Nutritional Deficiencies of Woody Ornamental
Plants Used in Florida Landscapes
R. D. Dickey
Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
F A ,Wnnrl lann fnr R pbarnh
Cover-Severe nitrogen deficiency symptoms of red maple
(Acer rubrum) growing in a landscape planting.
Nutritional Deficiencies of Woody Ornamental
Plants Used in Florida Landscapes
R. D. Dickey
Ornamental Horticulture Department
Florida Agricultural Experiment Stations
University of Florida, Gainesville
This public document was promulgated at an annual cost of
$8,369.60, or a cost of $.558 per copy to present informa-
tion on diagnosis and treatment of nutritional deficiencies
of woody ornamental plants used in Florida landscapes.
Mention of a trade name or proprietary product does not
constitute a guarantee or warranty of the product by the Uni-
versity of Florida and does not imply its approval to the ex-
clusion of other products that may also be suitable.
INTRODUCTION .......................................... 1
Deficiency Symptoms ................................... 1
Soil Conditions ....................................... 2
Species Susceptibility .................................. 3
NUTRITIONAL DEFICIENCIES ........................... 3
General Treatment of Nutritional Deficiencies ........... 3
MACRONUTRIENT DEFICIENCIES ....................... 4
Nitrogen Deficiency ................................. 4
Cause .......................................... 5
Symptoms ........................................ 5
Treatment ....................................... 5
Phosphorous Deficiency ................................ 6
Cause ............................................ 6
Symptoms ........................................ 7
Treatment ....................... ................ 7
Potassium Deficiency ................................ 7
Cause ............................. ............... 8
Symptoms ........................................ 8
General ....................................... 8
W ax-leaf privet ................................ 9
Treatment ......................................... 9
Magnesium Deficiency ................. ................ 10
Cause ................. ................ ........... 11
Symptoms .................................... .. 11
Treatment .......... ....... ................... 13
Soil application ................................ 17
Foliage spray ................................. 18
Calcium Deficiency ................................... 20
Cause ............................................. 21
Symptoms ....................... ................. 21
Treatment ......................................... 21
Sulfur Deficiency ...................................... 21
Cause .......................................... 22
Symptoms .............................. ........ 22
Treatment ......................................... 22
MICRONUTRIENT DEFICIENCIES ....................... 22
Manganese Deficiency .................................. 22
Cause .......................................... 24
Symptoms ........................................ 24
Treatment ........................................ 28
Soil application ................................ 28
Foliage spray ................................. 31
Iron Deficiency ....................................... 31
Cause ........................................ 32
Symptoms ........................................ 32
Treatment ........................................ 34
Soil application ................................ 34
Foliage spray ................................. 36
Zinc Deficiency ........................................ 37
Cause .......................................... 38
Symptoms ........................................ 40
Treatment ............................... ... ... 40
Soil application ........................ ........ 41
Foliage spray ................................. 41
Copper Deficiency ................................... 43
Cause .......................................... 45
Symptoms ........................................ 45
Treatment ........................................ 46
Soil application ................................ 47
Foliage spray ................................. 47
Molybdenum Deficiency ............................... 49
Cause ......................................... 49
Symptoms ........................................ 49
General ..................................... 49
Chinese hibiscus ............................... 50
Treatment ........................................ 51
Boron Deficiency .................................. 51
Cause .......................................... 52
Symptom s ..................................... 52
General ...................................... 52
Coconut ....................................... 52
Treatment ......................................... 53
General ...................................... 53
Coconut ....................................... 53
MULTIPLE DEFICIENCIES .............................. 53
Cause .......................................... 54
Symptoms ........................................ 54
Treatment ............................. .. ....... 55
Acid soils .................................... 55
Alkaline soils ................................. 56
SYMPTOMS OFTEN CONFUSED WITH THOSE
OF DEFICIENCIES .................................... 56
REFERENCES ............................................. 59
Nutritional Deficiencies of
Woody Ornamental Plants
Used in Florida Landscapes
The ornamental value of woody plants used in the landscape
is affected by placement and appearance. If these plants fail to
make a vigorous, thrifty growth, their ornamental value may be
materially reduced. Of the many environmental factors affecting
growth and vigor of woody ornamentals, nutritional deficiencies
are an important factor.
For approximately 60 years, much research has been done
on nutritional deficiencies of fruit, nut, vegetable, and agronomic
crops in Florida and, to a similar but lesser degree, with certain
woody ornamental plants (see reference section).
Mineral and organic soils of Florida are frequently deficient
in one or more nutrient elements essential to plant growth. Plants
growing in these soils will remain in an unhealthy condition,
though all other factors for good growth are present, until the
deficient element or elements are supplied.
Commercial citrus species and varieties (orange, grapefruit,
tangerine, tangelo, lemon, lime, etc.) are often used as orna-
mental plants. Information on nutritional deficiencies of citrus is
given in detail in other Experiment Station and Florida Extension
Service publications (9, 41, 51) and will not be discussed herein.
Some other plants grown for their fruit, but also used as orna-
mentals in Florida include: pecan, peach, pear, plum, black wal-
nut, muscadine grape, tung, avocado, and mango.
The term deficiency designates malnutrition conditions con-
sistently associated with symptom complexes evidenced by one
or more species. Where specific causes have been determined,
names used for these deficiencies are those of the deficient element
(manganese deficiency, iron deficiency, etc.) which will correct
the deficiency when applied to affected plants. Common names
in use for deficiencies are given, but they frequently describe
only one symptom of the complex. For example, the term "lime
chlorosis" is only one symptom of the iron deficiency symptom
complex. Sometimes two or more elements may be deficient at the
same time, and when this occurs all deficient elements must be
supplied before the deficiencies are corrected. Under these condi-
tions symptoms of one deficiency usually mask, to a considerable
degree, those normally produced by other deficiencies. However,
this may vary depending on species and deficiency combinations
Visual symptoms on leaves, twigs, fruit, and branches of af-
fected plants can be used as a reliable guide for identification of
nutritional deficiencies of woody ornamental plants in the field,
when diagnostic symptoms have been established by adequate
research, observations, and experience. Knowledge of deficiency
symptomology enables the trained observer to recognize defi-
ciencies in the field, and it helps him to make an educated guess
as to the causes of unidentified deficiencies, although identifica-
tion remains a guess until confirmed experimentally.
An element may be deficient for several reasons, most of
which relate to the soil. (a) An element may be leached from the
soil; this tendency is increased by acidic conditions. (b) An ele-
ment may be "fixed" in unavailable forms, as are iron, man-
ganese, zinc, etc., in highly calcareous soils. (c) An element may
be "cropped out" by removal in crops over a period of time pre-
vious to its use for ornamental plantings. (d) The native content
of previously uncultivated soils may be in the deficiency range
for certain plants. (e) Excessive levels of one element in the soil
may induce deficiency symptoms of a heavy metal element; for
example, iron deficiency induced by excessive amounts of copper
in the soil or copper deficiency induced by excessive phosphorous.
Deficiencies may develop because high levels of one element
inhibit uptake of other elements (antagonistic effects). Produc-
tion of deficiency symptoms or the intensification of already
present deficiency symptoms may be caused by factors causing
rapid growth, such as the application of nitrogen. The repressive
effect of one element on the uptake of another can be produced
by fertilization. For example, applying potassium where mag-
nesium is low may induce or intensify magnesium deficiency
symptoms. Some widely reported antagonistic effects are those
of calcium on potassium, calcium on magnesium, potassium on
magnesium, nitrogen on phosphorus, and nitrogen on potassium.
Application of nitrogen, because of its growth stimulating effect,
may produce or increase intensity of deficiency symptoms of
other elements that are at or near deficiency levels in plants. For
example, increasing nitrogen levels may induce or increase copper
and/or potassium deficiency symptoms (6, 18, 38).
Disease or nematode injury to the root systems and poor
drainage, with its accompanying poor aeration, reduce ability of
roots to take up nutrients from the soil. This may indirectly con-
tribute to development of deficiency symptoms. Generally, in-
creasing a soil's organic matter content increases its ability to
hold nutrient elements against leaching.
Species and variety differences in development of nutritional
deficiencies have been determined for many commercial crops.
The fact that, under similar growing conditions, some woody
ornamental species develop symptoms of these deficiencies while
others do not, suggests that there are specific differences in the
ability of the roots to forage for nutrients in short supply.
Those essential nutrient elements needed by plants in rela-
tively large amounts (nitrogen, phosphorus, potassium, calcium,
magnesium, sulfur) are commonly called major elements, while
elements required in relatively small amounts (copper, zinc, iron,
manganese, boron, molybdenum, chlorine) are referred to as
minor, secondary, or trace elements. These terms are misleading,
because the nutritional roles of copper, zinc, iron, and manganese,
for example, are no less important than those of major elements
such as nitrogen, potassium, calcium, or magnesium. For this
reason the more accurate terms of macronutrients for major ele-
ments and micronutrients for the minor, secondary, or trace
elements are used herein.
General Treatment of Nutritional Deficiencies
Spray and soil applications are the general methods used in
treating nutritional deficiencies of plants. Micronutrient spray
applications are most effective when made just before or during
a period of active growth, usually from spring to early summer.
Response as indicated by greening of chlorotic foliage and normal
growth coming from buds on affected shoots is usually observed
from 2 to 8 weeks after treatment, but response time varies de-
pending on species, age of plant and its parts (leaves, twigs,
branches), time of year, severity of the deficiency and soil con-
ditions under which plants are growing. Usually one or two appli-
cations during the year will prevent or control deficiencies, but
under some conditions it may be necessary to make several spray
treatments annually to maintain healthy growth. All of the
foliage should be covered with the spray, since only sprayed
portions of the plant respond. Macronutrients are usually sup-
plied to plants by soil applications, but under certain conditions
they may be applied as foliage sprays.
Soil treatments, when effective, are the most satisfactory
method of treatment because of ease of application and residual
Some suggest that home owners or commercial operators
should prevent or correct nutritional disorders, whether caused
by single or multiple element deficiencies, by use of a "shot gun"
(commercial or homemade) mixture containing several elements.
This idea has considerable merit, but also has some disadvan-
tages. If a foliage spray is to be used, the necessary spray equip-
ment may be lacking, or hand sprayers may not be adequate to
do the job on a large number of plants or several large plants.
Home owners living in communities having pest control com-
panies can hire the work done, but the cost may be prohibitive
for some. Iron sprays are a special problem; they sometimes are
ineffective and may burn the foliage of some species. Iron sulfate
and copper sulfate should not be used in the same spray (12).
Sprays containing iron, manganese, and copper will stain masonry
structures and walkways. Soil application of "shot gun" mixtures
is the more desirable method, when effective, but it also has
disadvantages. Much more manganese sulfate will be needed to
correct this deficiency on plants growing on highly calcareous
than on acid soils. Under this condition commercial mixtures at
recommended rates may not correct the manganese deficiency,
but to apply enough of the "shot gun" mixture to do this might
bring other elements (copper, zinc, boron) in the mixture to toxic
levels. Soil applications of zinc have generally not been successful
in correcting zinc deficiency on acid soils of central and southern
Florida and on calcareous coastal soils.
Apparently there is no one control method (soil or foliage
application) which satisfies all conditions throughout the state,
because response varies with the element deficient, soil type, soil
reaction (pH), plant species, and method of application.
Nitrogen deficiency is the most widespread of all nutritional
deficiencies affecting growth of woody ornamentals in Florida's
landscape planting. Plants can be grown in the landscape with-
out application of commercial forms of nitrogen, but their growth
and appearance, and thus their landscape value is improved by
its application, almost without exception. Generally, if other
factors are not limiting growth, the subsequent growth and ap-
pearance of plants is improved to a greater degree by nitrogen
than by any other essential element.
Generally, mineral soils of Florida are low to very low in
nitrogen, and this is especially true of light sandy soil types.
Nitrogen is readily leached from soils, especially the nitrate form
(N03), but ammonia (NH4) nitrogen is held on the cation ex-
change complex to some extent, and thus is less subject to leach-
ing than the nitrate form. Florida's organic soils are generally
higher in nitrogen and more retentive of it than its mineral
soils; thus they provide a more uniform supply of nitrogen for
Nitrogen intake by plants may be affected by levels of certain
other nutrient elements in the soil, but depression of nitrogen
uptake from this cause is usually of little practical importance.
Nitrogen deficiency appears first on older foliage as a uniform
loss of green color over the entire leaf, and may vary in intensity
from a pale yellowish-green in early stages to ivory color in
advanced stages (Cover). This uniform loss of green color serves
to distinguish nitrogen from magnesium and iron deficiencies
with which it might be confused (Fig. 2). Affected leaves are
thinner than normal, and are reduced in size and number. Nitro-
gen deficiency affects leaves over the entire plant with yellowing
more severe on fruiting branches of fruit trees.
Severely affected plants are stunted, foliage is sparse, dead
wood appears in the plant, and fruit size and quantity is reduced.
Nitrogen deficient plants grow slowly if at all, and are more
susceptible to cold injury than those adequately supplied with
nitrogen. Bud opening is delayed on some species of flowering
Small amounts of nitrogen are made available to plants by
decomposition of organic matter and by nitrifying bacteria which
convert urea to ammonia and ammonia to nitrate nitrogen. There-
fore, organic soils, and mineral soils with relatively high organic
matter content, release more nitrogen 'to plants than soils with
low organic matter content. Organic amendments do not release
enough nitrogen for plant growth and should not be used for this
Ammonium nitrate, sulfate of ammonia, nitrate of soda, po-
tassium nitrate, urea, and ammoniated superphosphate are ma-
terials commonly used to supply the nitrogen in N-P-K (nitrogen,
phosphoric acid, and potash) commercial fertilizers frequently
used in fertilizing woody ornamentals. Application rates of these
N-P-K fertilizers are based on the amount of nitrogen to be sup-
plied. Four applications per year of an 8-8-8 made in spring,
summer, fall, and winter at rates of 2 to 4 pounds per 100 square
feet will usually supply sufficient nitrogen for adequate growth.
If a higher analysis fertilizer such as 16-4-8 or similar formula
is used, apply half the above recommended rate (1 to 2 pounds
per 100 square feet). To supply only nitrogen by using a material
listed above, the amount to apply depends on percent nitrogen
in the fertilizer. For example, 1/2 to 1 pound of ammonium ni-
trate (33.5% nitrogen) per 100 square feet will supply approxi-
mately as much nitrogen as the recommended rate of 2 to 4
pounds of 8-8-8 applied to an area of the same size. Plant condi-
tion should be used as a guide for deciding whether an increased
nitrogen rate or more frequent fertilization is needed.
A noticeable improvement in green color of the foliage of
many woody ornamentals usually takes place within 1 to 3 weeks
after the application of nitrogen.
Phosphorus deficiency has not been identified on woody orna-
mentals growing in Florida's landscape plantings. There are prob-
ably several reasons: phophorus is readily taken up by plants;
the amount required for normal growth is about 10 to 13 times
less than their nitrogen requirement; and it is an ingredient of
mixed commercial fertilizers containing nitrogen, phosphoric
acid, and potash commonly used in fertilizing Florida's woody
Phosphorus is generally low in most Florida soils, except in
Arredondo and related series, which have developed from phos-
phatic materials. Some phosphorus may be lost by leaching es-
pecially in acid soils (below pH of 5.5) and by cropping, but phos-
phorus can easily be replenished. Though phosphorus is not in-
volved in cation exchange reactions, it is usually fixed more se-
curely in the soil than potassium, magnesium, and calcium. This
fixation takes place to a greater degree in clay and in calcareous
soils than in acid soils.
Phosphorus deficiency symptoms have been described for
many field crops agronomicc and vegetable), but generally woody
species will grow well in the field without phosphorus fertilization
on soils that require such fertilization for rapidly growing field
crops. For this reason little is known of phosphorus deficiency
symptoms of woody ornamentals growing in the field, and none
has been identified in Florida.
Superphosphate, treble superphosphate, and ammoniated
superphosphate are materials commonly used to supply the phos-
phoric acid (P20s) of N-P-K commercial fertilizers. Smith (8)
stated that "phosphorus deficiency is rare in citrus even where
none has been applied". This indicates the minimum amount of
phosphorus in relation to nitrogen and potassium that can be
obtained in commercial N-P-K fertilizers, should supply phos-
phorus needs of woody ornamental plants in Florida. Superphos-
phate contains, in addition to phosphorus, calcium sulfate (gyp-
sum), which also supplies the nutrient elements calcium and
sulfur. It also contains small amounts of molybdenum and fluorine
Application rates of N-P-K fertilizers are based on percentage
of nitrogen they contain. Therefore, application rates suggested
in the sections on nitrogen and potassium deficiencies should be
used. To supply only phosphorus, apply 0.8 to 1.6 pounds of super-
phosphate (20% phosphoric acid) per 100 square feet. This sup-
plies approximately as much phosphoric acid as the recommended
rate of 2 to 4 pounds of 8-8-8 applied to the same sized area.
Potassium deficiency was once common in commercial tung
plantings growing on some clay soils (Redbay, Ruston, Norfolk)
of northwestern Florida before adjustment of fertilizer programs
to prevent it. However, it has not been seen on tung in landscape
plantings, nor has it been observed on other woody ornamental
species growing over the same area. Potassium deficiency has
been identified on wax-leaf privet (Ligustrum japonicum) in
northern peninsular Florida growing on sandy soils under very
low fertilization levels. Symptoms similar to those identified as
potassium deficiency on dogwood (Cornus florida) and red maple
(Acer rubrum) elsewhere in the United States have been ob-
served on these plants in northern peninsular Florida. The fact
that potassium deficiency has been identified on only a few woody
ornamental species in Florida's landscape plantings is probably
because of the low nitrogen levels usually applied, use of chemical
fertilizers containing potassium and the ability of plants to toler-
ate a relatively wide range in foliage potassium (0.35% to 3.5%)
without showing deficiency symptoms.
Recognition of potassium deficiency of woody ornamentals
in Florida is further complicated by limited research information
on this problem and by the fact that symptoms of potassium and
magnesium deficiencies are frequently so similar in appearance
that foliage analyses in conjunction with corrective treatments
are often necessary to distinguish between them.
Florida soils are generally low in potassium, and experience
with many commercial crops has shown that good growth and
yields require repeated supply of potassium in fertilizers. Potas-
sium also is removed from the soil by cropping and by leaching,
which increases as soils become more acid. Excesses of calcium
and/or magnesium creates an imbalance of potassium to calcium
or potassium to magnesium, which reduces uptake of potassium
by plants and thus contributes to possible development of potas-
sium deficiency. When potassium supply in the soil is low, ap-
plication of nitrogen may induce potassium deficiency symptoms
or aggrevate already existing symptoms.
Generally, an interveinal chlorosis (yellowing of tissue be-
tween midrib and main and secondary veins) develops first on
leaves at base of shoots, and advances up the shoot as the season
progresses. This is followed by scorch which develops from the
margin inward with areas of dead tissue extending inward in
areas between main veins (Fig. 1); on some species margins of
these scorched leaves roll inward toward midribs. In advanced
stages much of the leaf surface dies, and scorched leaves may be
frayed resulting from loss of dead tissue. Early leaf drop may
occur later in the season. The time of symptom development is
variable, but it often appears from early summer until fall.
When potassium deficiency becomes chronic and acute, growth is
reduced, some limbs and branches die, and affected plants are
more susceptible to cold injury. On some species symptoms of
potassium and magnesium deficiencies are so similar it is difficult
to distinguish between them by visual symptoms only. Variations
from this general symptom pattern have been described for
several species as leaves of some turn blue-green; those of some
others show an interveinal speckling and browning in addition
to the marginal scorch; and leaves of some others show a purple
tinting before scorch appears. In other species some trees evi-
denced largely interveinal chlorosis; others developed mostly
necrosis (scorch and interveinal dead tissue); and other trees
first developed interveinal chlorosis followed by necrosis of the
chlorotic leaves, a pattern similar to that described above.
Chlorosis first appeared on the older mature leaves at base of
shoots and progressed towards shoot tips as the season advanced.
Chlorosis began at the tips of leaves as a loss of green color over
the entire chlorotic area, and in severe cases the affected area
enlarged to include all of the leaf surface except a small green
area at base of the leaf (Fig. 1). Depending on severity of the
deficiency, a few shoots to the entire plant were affected. Ir-
regularly shaped dead areas appeared in the chlorotic areas of
some leaves, but this is not a prominent symptom.
Increasing organic matter content of the soil, mulching
plants, and maintaining pH in a range of about 5.7 to 6.3 will
increase the soil's ability to hold potassium against leaching.
Prevention and/or correction of potassium deficiency consists
of supplying adequate amounts of potassium in the fertilizer.
Chemicals commonly used in commercial fertilizers to supply
potassium are potassium sulfate, potassium chloride (muriate of
potash), and potassium nitrate. Commercial fertilizers such as
an 8-8-8 (nitrogen, phosphoric acid, and potash) applied in the
spring, summer, fall, and winter at rates of 2 to 4 pounds per
100 square feet (1.6 to 3.2 ounces per 10 square feet) will usually
u -i -1U L VW-
Figure 1.-Severe potassium deficiency symptoms of wax-leaf
privet (Ligustrum japonicum) showing chlorosis and necrosis.
supply needed potassium. Apply about half the recommended
rates (1 to 2 pounds per 100 square feet) when using a higher
analysis fertilizer such as a 16-4-8 or similar formulas. When
potassium containing chemicals are used alone, apply them to
supply amount of potash (K20) contained in an 8-8-8 fertilizer
applied at a rate of 2 to 4 pounds per 100 square feet. This is
0.32 to 0.64 pound of potassium chloride, 0.3 to 0.6 pound of
potassium sulfate, or 0.35 to 0.7 pound of potassium nitrate per
100 square feet.
Magnesium deficiency was once widespread in Florida's com-
mercial citrus plantings and in commercial tung plantings that
previously existed in northern peninsular Florida. It occurred
less frequently on citrus growing in landscape plantings, and
has not been observed on tung used in this manner. Though mag-
nesium deficiency is less common than manganese and iron de-
ficiencies, it occurs to a considerable extent on several woody
ornamentals used in landscape plantings in the state, and is more
prevalent in peninsular than in northwestern Florida..
Woody ornamental species in Florida on which magnesium
deficiency has been identified or is suspected are given in Table
1. Further experimentation and observation should expand this
list considerably. Species most often showing magnesium de-
ficiency symptoms are citrus, Japanese pittosporum, Canary Is-
land date palm, nagi podocarpus, poinsettia, orchid-trees, yew
podocarpus, Chinese box-orange, and pigmy date palm. Species
and varieties of woody ornamentals show a difference in sus-
ceptibility to magnesium deficiency because some kinds may de-
velop symptoms while many others growing under similar soil
conditions may not. Research has shown (6) that magnesium
deficiency of citrus is closely associated with seediness; seedy
varieties of grapefruit and oranges were more susceptible to
magnesium deficiency than seedless or nearly seedless ones.
Heavily fruiting female plants of yew podocarpus have been ob-
served showing magnesium deficiency, while nearby fruitless
male plants evidenced none or only mild symptoms. Likewise
magnesium deficiency symptoms were further intensified by
heavy fruiting of female nagi podocarpus plants.
Magnesium deficiency of citrus is called "bronzing", but this
common name has also been applied to zinc deficiency of tung in
Florida, and is but one symptom of the deficiency complex.
Many Florida soils are low in magnesium, and in some cases
the low native supply has been further depleted by heavy crop-
ping. Magnesium is readily leached from acid sandy soils, and in
calcareous soils is "fixed" in relatively unavailable forms. The
antagnostic effect of calcium on uptake of magnesium is a factor
contributing to development of magnesium deficiency in plants
growing on calcareous soils. Clay soils (Redbay, Ruston, Orange-
burg, Norfolk, Greenville, Tifton, and related series) of north-
western Florida apparently supply more available magnesium
than sands and calcareous soils, because magnesium deficiency
has not been seen on woody ornamental species growing on these
clay soils. Heavy applications of potassium to tung and citrus in
Florida have caused magnesium deficiency symptoms or aggre-
vated existing symptoms by further depressing magnesium in-
take. Under similar soil conditions some other woody ornamental
species should respond similarly.
Generally foliage is a normal green on growth flushes in the
spring, but as the season progresses an interveinal chlorosis
develops on these maturing leaves from early summer to fall.
Table 1. Woody ornamental species in Florida on which mag-
nesium deficiency has been identified experimentally or is sus-
pected as the cause.
Magnesium deficiency identified experimentally
Aleurites fordi Tung tree
Bauhinia purpurea Orchid-tree
Bauhinia variegata Orchid-tree
Carya illinoensis Pecan
Citrus spp. Citrus species and varieties
Euphorbia pulcherrima Poinsettia
Phoenix canariensis Canary Island date palm
Pittosporum tobira Japanese, pittosporum
Podocarpus nagi Nagi podocarpus
Vitis rotundifolia Muscadine grape
Magnesium deficiency suspected as cause
Butia capitata Butia palm
Cercis canadensis Redbud
Feijoa sellowiana Feijoa
Hibiscus rosa-sinensis Chinese hibiscus
Ilex opaca American holly
Ixora coccinea Scarlet ixora
Jasminum mesnyi Primrose jasmine
Ligustrum japonicum Wax-leaf privet
Malvaviscus arboreus Turk's cap
Murraya paniculata Orange-jessamine
Paurotis wright Saw cabbage palmetto
Phoenix reclinata Senegal date palm
Phoenix roebeleni Pigmy date palm
Podocarpus macrophylla Yew podocarpus
Sabal palmetto Cabbage palmetto
Severinia buxifolia Chinese box-orange
Spiraea cantoniensis Reeves spirea
Tecomaria capensis Cape-honeysuckle
Viburnum suspensum Sandankwa viburnum
Chlorosis begins on leaves at base of shoots and advances toward
the tip as the leaves mature and the season progresses. The pat-
tern of chlorosis development and intensity of yellowing of the
foliage depend on species, age of leaves, and duration and in-
tensity of the deficiency. In early stages of chlorosis development,
unconnected areas, irregular in extent and outline, developed
between the midrib and main lateral veins over all or part of
the leaf. In severe cases these chlorotic areas enlarge and merge
to form large yellow areas which may cover all or nearly all of
the leaf except an inverted V-shaped area at base of the leaf
(Japanese pittosporum, citrus) (Fig. 2A). Some species evidence
only a chlorosis of the foliage but no necrosis (Japanese pit-
tosporum, nagi podocarpus, yew podocarpus, Canary Island date
palm, Chinese box-orange, orange-jessamine, cape-honeysuckle,
pigmy date palm, citrus), while necrosis (which may develop as
marginal scorch or tip burn, and/or interveinal necrosis) may
accompany the chlorosis on other species (poinsettia, orchid-
trees, Reeves spirea, wax-leaf privet, tung, muscadine grape)
(Fig. 2B). There are variations from this characteristic pattern
of chlorosis. Chlorosis of nagi podocarpus begins as a band of
yellow tissue near the middle or in the tip half of the leaf which
may enlarge to cover all the leaf except small green areas at the
base and tip (Fig. 3). Chlorosis of Canary Island date palm de-
velops as a fading of the green color of the leaf's individual leaf-
lets from their tips toward their bases. Older leaves on a tree,
which persist for several years, show symptoms while upper
leaves are a normal green color (Fig. 4).
Magnesium deficient plants may drop leaves that have lost
most of their green color, with leaf drop starting at base of
shoots and progressing towards the tips. Though normal green
leaves remain at the tips of many shoots, there are usually some
shoots on a plant on which all leaves show symptoms. Leaf drop
is usually more pronounced on species that fruit heavily (yew
and nagi podocarpus, American holly, citrus) and plants sub-
jected to adverse environmental conditions such as drought, cold
weather, and poor drainage. Pesticide sprays also increase leaf
drop. The degree to which symptoms develop on an affected
plant may vary from only a few scattered shoots showing sym-
toms to nearly all of the shoots with symptoms.
Leaf size was not materially reduced nor were there any
primary symptoms on shoots attributable to magnesium de-
ficiency of the plants listed in Table 1.
Since severe magnesium deficiency greatly increased sus-
ceptibility of citrus to cold damage (6), it seems likely that some
other severely affected woody ornamentals may be susceptible
for the same reason.
Magnesium deficiency of most woody fruit and ornamental
species is often difficult to control under field conditions by either
soil or foliage applications of magnesium, but several species
have responded satisfactorily to either or both of these treat-
ments. Correction of magnesium deficiency by soil applications
Figure 2A.-Magnesium deficiency symptoms: branch of Japa-
nese pittosporum showing foliage chlorosis which started on older
leaves at base of shoot.
Figure 2B.-Magnesium deficiency symptoms on shoot of
poinsettia plant growing in the field, showing chlorosis and
Table 2. Approximate pounds of ground limestone or dolomite lime required to increase Florida's sandy soils
one unit of pH.1
Soil Soil content of organic matter low Soil content of organic matter moderate
Texture2 Lbs. per Lbs. per Lbs. per Lbs. per Lbs. per Lbs. per
10 sq. ft. 100 sq. ft. 1,000 sq. ft. 10 sq. ft. 100 sq. ft. 1,000 sq. ft.
Sand 0.4 3.7 37 0.7 7.0 70
Loamy sand 0.5 4.7 47 0.8 8.4 84
Sandy loam 0.6 6.0 60 0.9 9.3 93
Sandy clay loam 0.9 9.3 93 1.1 10.9 109
1J. NeSmith and E.W. McElwee. 1971. Soil reaction (pH) for flowers, shrubs, and lawn around the home.
2Listed in order of increasing clay content.
of magnesium sulfate and/or dolomite (magnesium and calcium
carbonates) has been obtained on citrus and tung in Florida in
a reasonable length of time (1 to 4 years), but response to soil
applications of magnesium sulfate by Japanese pittosporum,
nagi podocarpus, wax-leaf privet, and Canary Island date palm,
growing on acid sandy soils in the Gainesville area (22), has
been slow and irregular as has response to soil applications by
citrus and lime, especially, on calcareous soils of Florida's lower
Adjusting pH of acid soils to between 5.5 to 6.5 by liming
(Table 2) and increasing organic matter content increases their
ability to retain magnesium against leaching, and lowering pH
of calcareous soils by application of soil acidifying materials
(see iron deficiency section) increases availability of magnesium.
The best method of control is to prevent magnesium de-
ficiency from developing. Apply dolomite (about one-half is mag-
nesium carbonate) to acid soil area where woody ornamentals
(shrubs, vines, trees, palms) are to be planted to adjust pH
to the desired range as a preventive measure, and simultaneous-
ly supply a source of slowly available magnesium. Amount to
apply depends on soil pH, texture, and organic matter content,
but can be determined from information given in Table 2. For
example, if pH of a sandy soil low in organic matter is 5.0 and
it is desired to raise it to 6.0, this requires an application of
dolomite to the soil of 0.4 pound per 10 square feet, 3.7 pounds
per 100 square feet, or 37 pounds per 1,000 square feet (Table
2). Spread the dolomite evenly over the area to be treated and
incorporate it into the soil to a depth of 6 to 12 inches.
When magnesium deficiency has developed and become
chronic and acute on established woody landscape plants, satis-
factory control is difficult to obtain. Woody ornamentals respond
slowly under these conditions, and magnesium is readily leached
from the soil; therefore, repeated soil applications over a period
of years may be required for correction and control. Apply mag-
nesium sulfate (epsom salt) twice yearly (February or March
and June or July) at rates of 500 to 1000 pounds per acre per
application. One teaspoon per square foot, 3 tablespoons per
square yard, or 2 cups (1 pound) per 100 square feet applies
magnesium sulfate at a rate of 500 pounds per acre. Apply the
magnesium sulfate evenly under spread of plants and wash in
Figure 3.-Magnesium deficiency symptoms: branches of Podo-
carpus nagi showing chlorosis pattern characteristic of this plant.
with water. Repeat these applications yearly until symptoms
disappear. Large plants such as mature trees of nagi podocar-
pus and Canary Island date palm showing severe symptoms
should be given from 4 to 8 pounds of magnesium sulfate per
application. After magnesium deficiency has been corrected, it
can be prevented from reoccuring by applying magnesium sul-
fate (1% to 3% MgO) in the fertilizer. Best control has been
obtained on acid soils when both dolomite and magnesium sul-
fate (32) were applied.
Magnesium sulfate sprays generally have been unsuccessful
in correcting magnesium deficiency on most woody species. Some
success has been reported in correcting this deficiency with mag-
nesium nitrate sprays on orange trees in California and on mar-
cotted limes in Florida (34, 40); but foliage sprays are not
recommended because of inconsistent results due to species dif-
` ~ cK
,__ ,_ M. ;i I
Figure 4.-Magnesium deficiency symptoms on older leaves of
ferences, growth condition, climatic factors, season of the year,
number of applications required, possibility of spray burn es-
pecially from repeated applications, limited information relative
to use on woody ornamentals, and the fact that foliage pro-
duced following treatment may show symptoms. If other control
measures have been ineffective, sprays should be tested on a
small group of plants of each affected species to determine its
effectiveness and safety before general use. A suggested rate is
10 pounds of magnesium nitrate in 100 gallons of water (3.2
ounces in 2 gallons of water to foliage flushes that are two-
thirds to three-fourths expanded). Magnesium nitrate is ex-
pensive, hard to obtain, and hydroscopic, making it hard to
store. Success in correcting magnesium deficiency of citrus ob-
tained from applications of a spray composed of 10 pounds of
magnesium sulfate plus 10 pounds of calcium nitrate in 100
gallons of water suggests trying this spray on woody orna-
mentals when other control methods have failed.
Calcium (lime) deficiency has not been identified on woody
ornamental species growing in Florida's landscape plantings.
Factors contributing to this are low nitrogen levels usually ap-
plied, calcium in irrigation water, calcium sulfate (gypsum) in
superphosphate, and calcium materials used as fillers in commer-
- Calcium functions as a plant nutrient and indirectly affects
// soil fertility. A beneficial effect of calcium is that it adjusts
soil reaction of acid soils to the desirable pH range of 5.5 to
6.5; this adjustment in pH reduces losses by leaching of phos-
phorous and ammonia and of the cation exchange elements po-
tassium, magnesium, calcium, manganese, iron, zinc, copper,
and boron. The desirable pH range improves the growth of bene-
ficial soil organisms, increases availability of molybdenum, and
reduces injury from toxic elements such as aluminum and excess
copper (common in old citrus orchard soils). High calcium
levels can have some harmful effects. High calcium levels in-
crease the pH above the desirable range; this in turn reduces
the availability of the nutrient elements manganese, iron, zinc,
copper, boron, and magnesium. Too much calcium also depresses
uptake of potassium and magnesium, and reduces phosphorous
availability by forming the relatively unavailable tricalcium
The amount of available calcium in Florida soils is variable
but is relatively low in light sandy acid soils. Some calcium is
lost by leaching, especially in very acid soils; by fertilizing with
acid residue materials; and by cropping. However, woody plants
usually obtain sufficient calcium from the soil for normal growth.
Necessary liming of very acid soils will correct this excessive
There is no information available from field experiments on
calcium deficiency symptoms of Florida's woody ornamental
Application of calcium as a nutrient element to woody orna-
mentals in Florida is not required. However, if areas to be land-
scaped are strongly acid (pH below about 5.5) it will be desir-
able to apply calcium to adjust to the more desirable pH range
of 5.5 to 6.5 (15) to improve availability of other elements. Ma-
terials commonly used to supply calcium are agricultural lime-
stone, hydrated lime, and dolomite-which contains calcium and
magnesium. If the only consideration is pH control, the best
material to use would be agricultural limestone. However, acid
sandy soils of Florida are usually low in magnesium; therefore,
dolomite should be used to adjust soil reaction and also to supply
Amounts of liming materials needed to adjust pH of the soil
are given in Table 2; this varies with the soil type, pH, and or-
ganic matter content. Mix liming materials with the soil to a
depth of 6 to 12 inches, where possible.
Sulfur deficiency has not been identified on any woody orna-
mental plants in Florida. Sulfur and phosphorus requirements
of woody plants are similar, and less of both is usually needed
than the other macroelements.
Enough sulfur for normal plant growth may be provided by
sulfur in the soil, supplied in irrigation water, deposited by rain-
fall (1 pound per acre per 1 inch of rainfall), produced from de-
composition of organic matter, and supplied by commonly used
fertilizer materials (calcium sulfate in superphosphate, am-
monium sulfate, potassium sulfate, etc.).
Sulfur is lost from soil by leaching and by cropping, but is
replaced from sources mentioned. Therefore, woody ornamentals
growing in Florida normally will not develop sulfur deficiency.
Foliage symptoms of sulfur deficiency are similar to those
of nitrogen deficiency, as leaves become a pale yellow, but this
chlorosis occurs on younger rather than on the older leaves.
Total growth is reduced in severe cases.
For reasons given above application of sulfur containing fer-
tilizer materials solely for the purpose of preventing or correct-
ing sulfur deficiency is not necessary.
Manganese deficiency is one of the two most prevalent micro-
nutrient deficiencies of woody ornamentals in Florida. Several
woody species showing manganese deficiency have been observed
throughout the state, but this deficiency is much more pre-
valent in peninsular than in northwestern Florida. Manganese
deficiency is common on acid sandy soils and over-limed soils of
interior peninsular Florida, and is most prevalent and acute on
calcareous soils (alkaline sands and marl soils) of coastal areas.
Woody ornamental plants in Florida on which manganese de-
ficiency has been identified, or is suspected, are given in Table
3. Further observation and experimentation will likely increase
this list. Under similar growing conditions many plants of Bou-
gainvillea glabra cv. 'Sanderiana' show manganese deficiency,
while only an occasional plant of cv. 'Crimson Lake' is affected.
Manganese deficiency of several woody ornamental species
in Florida is sometimes called frenching; that of the queen and
royal palms has variously been called "frizzle leaf", "curly top",
"curly bud", and "curly leaf"; and that of the pecan "mouse ear"
(little leaf). However these common names are only part of the
manganese deficiency symptom complex of these plants.
Table 3. Woody ornamental species in Florida on which man-
ganese deficiency has been identified experimentally or is sus-
pected as the cause.
Manganese deficiency identified experimentally
A leurites fordi
A leurites montana
A recastrum romanzoffianum
Tufted fish-tail palm
Citrus species and varieties
Canary Island date palm
Pigmy date palm
Manganese deficiency suspected as cause
Saw cabbage palm
Many Florida soils, especially acid sandy ones low in organic
matter and cation exchange capacity, are natively low in man-
ganese. They are further depleted by leaching by the cumulative
effects of acid-residue fertilizers over a period of years or, in
some cases, by cropping prior to use for ornamental plantings.
A pH range of 5.5 to 6.5 is best for availability and utilization of
manganese by the plant. As the soil reaction becomes more acid
(below 5.5), leaching increases; and as the soil becomes alkaline
(pH 7.0 and above) manganese is "fixed" and becomes relatively
unavailable to plants. This explains why manganese deficiency
is more prevalent and acute on over-limed acid soils already low
in manganese and calcareous soils of coastal areas. Over-liming
of normally acid soils around buildings frequently results from
lime mixed with the soil during construction, or washed from
walls and foundations of masonry buildings, or from lime rock
used in road beds. The high fixing power of alkaline soils for
manganese is shown by an experiment with citrus in which it
was found that less than 1 pound of available manganese per
acre was extractable from the soil 1 year after manganese sul-
fate had been applied at the rate of 1,000 pounds per acre (7).
Manganese deficiency has been only occasionally observed on
woody ornamental species growing on the clay soils (Red Bay,
Ruston, Norfolk, Orangeburg, Tifton, and related series) of
Manganese deficiency symptoms first appear on young, de-
veloping foliage at shoot terminals soon after it emerges from
the bud. The degree of symptoms that plants show may range
from a few chlorotic leaves on one shoot to virtually all leaves
chlorotic on a mature plant as in severe cases of manganese de-
ficiency of allamanda, crape-myrtle, and the camphor tree.
Manganese deficiency has shown a wide variety of symptom
patterns which may be classified into three principal types:
(a) chlorosis, which is usually interveinal (yellowing of tissue
between midrib and main veins) but may also include the entire
leaf; (b) reduction in size of plant parts (leaves, shoots, fruit,
trunk); and (c) necrosis (dead tissue), which may be evidenced
as dead spots or extensive dead areas of leaves, leaf drop, dead
branches, and in some cases death of the entire plant. These
three types of manganese deficiency symptoms have appeared
on woody ornamentals in Florida in these symptom complexes
(patterns) : (a) chlorosis as principal symptom plus necrosis
(spotting) on some species; (b) reduction in size of plant parts
and necrosis; and (c) chlorosis with reduction in size of plant
parts and necrosis.
Interveinal chlorosis of leaves is the characteristic symptom
(Fig. 5A, B) of several woody ornamental species on which man-
ganese deficiency has been identified (allamanda, bougainvillea,
crape-myrtle, cattley guave, flame vine, Bengal clock-vine, dog-
wood, camphor tree, butterfly-bush, cape plumbago, furry jas-
mine, citrus, wax-leaf privet, glossy privet, crape-jasmine, sweet
viburnum, Japanese pittosporum, agyneja-Table 3). These
plants showed no visible reduction in leaf size. Amount of
chlorotic leaf area and intensity of yellowing varied with the
age of the leaves, plant species, and severity and duration of the
deficiency. Severely affected plants of some species (crape-jas-
mine and rusty fig) showed foliage symptoms that could not be
distinguished from those of iron deficiency, until identified ex-
perimentally, because many severely affected leaves lost all green
color and were entirely yellow (Fig. 6). Manganese deficiency
of tung and Bengal clock-vine is an example of interveinal chloro-
sis with necrosis (dead spots in chlorotic areas) and no visible
reduction in leaf size (Fig. 7).
The manganese deficiency of pecan symptom complex appears
as a reduction in leaf size and necrosis. In mild stages leaflets
may be normal in size with only the ends rounded. Acutely af-
fected leaflets, as compared with normal large long-pointed
leaflets, are severely dwarfed, and they have blunt tips which
may be rounded, indented at the midrib, or irregularly shaped
resulting from marginal scorch of tissue in terminal area of
leaflets. Midribs of severely affected leaflets and midrib of the
compound leaf are shortened. The leaflets or leaf blades are
cupped in varying degree and somewhat wrinkled, from which
has come the term "mouse car" (Fig. 8). Occasionally, trees are so
severely affected that some top branches die (37). This deficien-
cy is most often found on pecans growing in landscape plantings
where the soil pH is 6.8 to 7.4 and above. This high pH may
occur naturally in calcareous soils near coastal areas, or may be
produced on acid soils from lime mixed with it during building
or paving operations.
Manganese deficiency of queen, royal, and other palms de-
veloped the three basic types of symptoms previously mentioned:
Figure 5A.-Manganese deficiency symptoms: (left) allamanda
shoot showing interveinal chlorosis and (right) normal shoot.
chlorosis, reduction in growth of leaves and trunks, and necrosis.
Chlorosis of leaves is the first symptom to appear on affected
plants. Compared with normal green leaves, leaflets of deficient
leaves are light green to greenish yellow in color. The degree of
color loss depends on severity of the deficiency. Affected leaflets
appear streaked, since the tissue between the veins is lighter
green than the veins. Young leaves unfolding from the bud may,
in advanced stages, be pale yellow in color. In acute stages leaves
are much reduced in size, individual leaflets are chlorotic and
small, and the entire leaf presents a characteristic "frizzle leaf"
appearance. Necrotic areas appear in leaflets in varying degree,
and in severe cases much of the leaf area is killed (Fig. 9).
Figure 5B.-Manganese deficiency symptoms of crape-myrtle:
(left) shoot showing severe interveinal chlorosis and anthocyanin
pigment, (center) normal shoot, and (right) shoot with moderate
Growth of the trunk immediately below the leaf crown, in
chronic and acute cases, may be so severely reduced in diameter
that it produces a "bottle neck" effect. In some cases a later in-
crease in growth may produce an "hour glass" effect. These con-
ditions considerably reduce the ornamental value of affected
plants. In final stages, growth is so reduced that the palm is un-
able to put out leaves and finally dies.
Figure 6.-Manganese deficiency symptoms of rusty fig (Ficus
rubiginosa): (left) untreated chlorotic shoot, showing symptoms
similar to those of iron deficiency; (right) an affected shoot 10
weeks after treatment with a 1% manganese-lime solution.
This is the better method because of ease of application and
long lasting effect, but may not always be effective. The amount to
apply varies with species, age and size of plant, soil type and pH,
and severity of the deficiency. Application rates of manganese
sulfate for woody ornamentals growing on acid soils may range
from 1 to 2 ounces per plant to 5 pounds per tree for mature
pecan trees and queen and royal palms. Soil applications of man-
ganese sulfate on calcareous sandy soils, ranging in pH from
6.8 to 8.2, have corrected manganese deficiency of crape-myrtle,
allamanda, cattley guava, sweet viburnum, cape plumbago, flame
vine, bougainvillea, pecan, queen and royal palms (Fig. 9), and
Canary Island date palm (11, 14). Amounts applied ranged
from 4 ounces per plant for small plants to 10 pounds per tree
for mature pecan trees, but 1/ to 1 pound per plant corrected the
deficiency on several shrubs and vines tested. However, soil ap-
plications of manganese sulfate to camphor trees, crape-jasmine,
and citrus on calcareous sandy soils were unsuccessful. Man-
Figure 7.-Tung leaves showing steps in development of man-
ganese deficiency symptoms-chlorosis and necrosis. Young leaf
is at upper left. Symptoms of chlorosis become more severe as
leaves mature, and leaf at lower right shows necrosis.
Figure 8.-Manganese deficiency symptoms ("mouse ear")
of pecan showing reduction in size of individual leaflets, rounded
ends of leaflets, leaflets with cupped and wrinkled blades, and
necrosis at leaflet terminals.
.. .. j.I I.-_.. -* i
Figure 9.-Left: Queen palm showing acute symptoms of man-
ganese deficiency-reduction of leaf size, "frizzle leaf," and leaf
necrosis. This tree was treated with 1% manganese-lime spray
plus 2 pounds of manganese sulfate applied to the soil on May 13,
1941, and March 11, 1942. The photograph was taken when first
treated. Right: Same palm, photographed June 26, 1942. The
manganese treatments have effected complete control of man-
ganese soil applications on marl soils of the Miami-Homestead
area are generally unsuccessful in correcting manganese de-
ficiency of woody ornamentals because of high manganese fixing
power of these soils.
Soil applications of manganese sulfate should be made by
broadcasting it evenly under spread of the branches or canopy,
or by broadcasting it in a cleared circle around the base of plants
growing in lawns. If this cleared circle is not maintained it is
better to apply the manganese by "plugging" rather than broad-
cast. Make applications at any time manganese deficiency is ob-
served on affected plants but preferably in spring or early sum-
mer. In experiments with mature queen palms one application
per year was as good as two, provided sufficient manganese was
applied. Repeat treatments until desired response is obtained.
Once manganese deficiency has been corrected, additional soil ap-
plications should be made only when the deficiency reoccurs.
Generally, soil applications take longer than foliage sprays to
correct manganese deficiency, and from 1 to 6 months may be
required for complete response.
Sometimes concentrating the amount applied into smaller
areas by "plugging" into holes distributed under spread of the
crown or in narrow trenches located at outer edge of plant's
canopy may improve response to manganese applications on cal-
Manganese deficiencies can be quickly corrected with foliage
sprays, and often this is the only satisfactory way to correct
symptoms on plants growing on calcareous soils. A disadvantage
is that spray treatments usually must be applied yearly to pre-
vent reoccurrence of the deficiency.
Spray applications are most effective when made just before
or during a period of active growth. Therefore, from spring to
early summer is usually the best time to spray. Generally, re-
sponse of chlorotic foliage is seen within 2 to 8 weeks, but im-
provement of palms is evidenced by emergence of normal leaves
from the bud, and this may require 3 to 6 months (11). Usually
one or two applications will correct the deficiency; however, un-
der some conditions several sprays will be required to maintain
healthy growth. Cover all the foliage with the spray, as only that
portion responds which has been sprayed. A manganese-lime
spray is made by dissolving 3 pounds of manganese sulfate
(23% to 25% manganese) and 3 ounces of hydrated lime in 100
gallons of water (1 tablespoon of manganese sulfate and 1 tea-
spoon of hydrated lime in 2 gallons of water-Table 8).
Severely affected plants may benefit from a combined treat-
ment of a foliage spray for its immediate response and soil
applications for long range effects.
Iron deficiency is one of the two most prevalent micronutrient
deficiencies of woody ornamental plantings in Florida. Many
woody ornamental species showing iron deficiency have been
observed throughout Florida, but it is much more prevalent and
severe on plants growing on calcareous soils (alkaline sands and
marl soils) of peninsular Florida's coastal areas and localized
over-limed areas of acid soils. Though less prevalent it does occur
on acid soils especially on azalea, gardenia, ixora, and citrus.
Woody ornamental plants in Florida on which iron deficiency
has been identified or is suspected are given in Table 4. Further
observations and research should increase this list. Woody orna-
mental species vary in their susceptibility to iron deficiency.
Plants such as ixora, azalea, hibiscus, and gardenia may show
severe iron deficiency symptoms while other species growing
nearby show none or only mild symptoms.
Iron deficiency is sometimes called lime chlorosis, lime in-
duced chlorosis, marl chlorosis, chlorosis, or frenching. These
common names are descriptive of only one symptom of the iron
deficiency symptom complex.
Generally, iron deficiency is not caused by a deficiency of iron
in the soil but by unavailability of iron to plants. An alkaline
soil reaction (pH 7.0 and above) caused by excess lime (calcium
carbonate) in the soil is the most important factor causing iron
deficiency of woody ornamentals in Florida. Excess lime in the
soil "fixes" iron in a form unavailable to plants, which explains
why iron deficiency of woody ornamental plants is much more
prevalent and severe on localized over-limed areas of acid soils
and on alkaline sands and marl soils of coastal Florida. Some
acid sandy soils of inland central Florida are low in iron, es-
pecially sandy areas near lakes and places known as "sand
soaks" or "sand scrubs". This is also true for sandy beach soils,
and the problem is further complicated because soils in these
locations are frequently alkaline.
An excess of heavy metal nutrient elements in the soil such
as copper, zinc, or manganese can also produce iron deficiency.
This excessive buildup of copper, and subsequent development
of iron deficiency, has occurred in some locations in central
Florida on citrus, vegetable, and gladiolus growing on acid soils
that had been fertilized and/or sprayed with copper for several
years. If these soils with excess copper are later used for land-
scape plantings, this increases the possibility of iron deficiency
developing, especially on susceptible plants.
Characteristic iron deficiency symptoms first appear on young
leaves at shoot terminals as a pronounced chlorosis of the foliage
in which leaves are yellow with the veins appearing as fine green
Table 4. Woody ornamental species in Florida on which iron
deficiency has been identified experimentally or is suspected as
Iron deficiency identified experimentally
A leurites fordi
A verrhoa carambola
Citrus species and varieties
Iron deficiency suspected as cause
lines. In advanced stages some leaves on affected plants may be
entirely yellow (Fig. 10A). Foliage chlorosis symptoms of iron
deficiency is sometimes difficult to distinguish from that of
severe manganese deficiency of some plant species (rusty fig-
Fig. 6). As iron deficiency increases in severity, young develop-
ing leaves are dwarfed, dead spots and tip and/or marginal burn
develops on some leaves, plant growth is reduced or may cease,
some affected leaves drop, and dead wood appears in the plants
(Fig 10A, B). Amount and severity of iron deficiency symptoms
evidenced by plants may vary from development of chlorosis of
leaves on a few shoot terminals to development of all stages of
the iron deficiency symptom complex on severely affected plants,
and some plants may die.
Iron deficiency has long been the most difficult micronutrient
deficiency to control, especially by soil applications. Iron de-
ficiency has been corrected by soil or foliage applications (except
iron foliage sprays on citrus and gardenia) throughout Florida,
but soil application is the more desirable method because of long
lasting effect and ease of application.
Soil applications of iron compounds such as iron sulfate
produce, at best, inconsistent results even on acid soils, and
are generally unsatisfactory on calcareous soils. With advent of
the use of iron chelates on citrus in the early 1950's (42, 43),
satisfactory control by soil applications can now be obtained on
many acid and alkaline soils.
An acid soil reaction, adequate soil organic matter, and an
organic mulch are desirable growing conditions that reduce the
possibility of iron deficiency. If the soil is not naturally well
supplied with organic matter, then acid peat, muck, compost, or
leafmold should be mixed with the soil in areas where plants are
to be set. Frequently soil around new houses-block, brick, or
stucco particularly-is contaminated with lime in the mortar
spilled from the walls or foundations. This contaminated soil
should be removed and the bed filled with soil which is acid
If the soil is alkaline (pH 7.0 and above) it should be treated
with a soil acidifying material. Ordinary agricultural sulfur will
usually correct the trouble in a reasonable time, but finely ground
dusting or wettable sulfurs are more satisfactory since they
react more rapidly. A mixture of 3 parts dusting sulfur and 1
part iron sulfate is a good acidifying agent, as it not only
acidifies the solil but supplies iron that may be deficient. Use
Figure 10A.-Iron deficiency symptoms of 'Formosa' azalea:
shoots show mild (left), moderate (center), and severe (right)
Figure 10B.-Plants of Ixoria coccinea showing acute iron de-
V -4) 1.4:
sulfur and mixtures containing sulfur at rate of 1 pound per
100 square feet (1.6 ounces per 10 square feet) per application,
and do not use more than two or three applications per year.
At least 6 to 8 weeks should elapse between applications. Acidify-
ing materials should be incorporated into top 6 to 8 inches of
soil, whenever possible. This treatment is usually successful on
localized areas (over-limed and alkaline soils), but is impractical
for use on extensive areas of calcareous coastal soils, where at
best the acidifying effects are temporary.
Iron deficiency of woody ornamental plants can be corrected
by soil applications of iron chelates. The iron chelate of ethylene-
diamine tetraacetic acid (FeEDTA) has proved effective in cor-
recting iron deficiency of ornamental plants on acid soils (below
pH 7.0) but not on alkaline ones. For alkaline soils (pH 7.0 and
above) the iron chelate of sodium ferric diethylenetriamine penta-
acetate (Fe-DTPA-Sequestrene 330)1 and iron chelate of hydro-
xyethyl ethylenediamine triacetic acid (Fe-EDTA-OH-Versi-
nol)2 are effective on most calcareous soils. For calcareous soils
where these chelates do not correct iron deficiency (Rockdale
and related marl soils), good results can be obtained by using
the iron chelate of ethylene diamine di (o-hydroxphenyl) acetic
acid (FeEDDHA-Sequestrene 138)1. However, this chelate is ex-
pensive and should be applied only to those soils where response
is not obtained from either Fe-DTPA or Fe-EDTA-OH. Fe
EDDHA is not effective on acid soils. Time required for re-
sponse varies from 1 to 6 months depending on species and size
of plant, amount and kind of chelate applied, season of the
year, soil pH and type, and severity of the disorder. Maximum
efficiency is obtained from iron chelates when they are applied
to moist soil around plants and irrigated or dissolved in water
and applied about the plants as a drench. Because iron chelates
are effective in relatively small amounts and excessive levels may
injure the plant, manufacturers' directions should be carefully
Sometimes when an immediate correction of iron deficiency
is wanted and there is a delayed response to soil applications
'Sequestrene-Manufactured by Ciba-Geigy Corporation, Agrichem-
ical Division, Box 11422, Greensboro, North Carolina.
2Versinol-Manufactured by Hampshire Chemical Co.-Sold by
Traylor Chemical and Supply Company, Orlando, Florida.
of iron chelates, iron sprays may be used (ineffective on citrus
and gardenia). Disadvantages of iron sprays are: (a) they are
more difficult to apply than soil applications; (b) they will stain
brick or concrete structures and sidewalks and driveways; (c)
they leave an undesirable residue on the plant; and (d) each
time new leaves are produced by iron deficient plants, another
spray must be applied to green-up the chlorotic foliage. Irregular
response may be obtained on species from iron sprays, especially
when applied to severely affected old foliage. Apply the spray
at the rate of 2 to 4 pounds of iron sulfate per 100 gallons of
water (1/3 to 2/3 ounce of iron sulfate to 1 gallon of water) to
which has been added a small amount of a suitable spreader or
'detergent. Response may be observed 2 to 3 weeks following
treatment. Foliage sprays may injure young foliage of some
woody ornamentals at the higher rates.
Iron chelate sprays have been known to burn certain plants,
so if using them on plants other than those on which they are
known to be safe, test them on a small group of plants before
Zinc deficiency was once widespread in commercial pecan and
tung plantings in north and northwestern Florida. However,
pecans, peaches, pears, black walnut, satsuma orange, and
oriental persimmon in landscape plantings are also affected
from time to time over this area. Zinc deficiency of species and
types of citrus was once widespread over the state's citrus
growing areas, but occurs less frequently on citrus used in
landscape plantings. Zinc deficiency is not common on woody
ornamentals in peninsular Florida, and when present occurs
largely on plants growing on the calcareous coastal soils, though
it is sometimes seen on plants growing on acid soils.
Woody ornamentals in Florida on which zinc deficiency has
been identified or is suspected are given in Table 5. Observa-
tions and research should increase this list considerably. In
peninsular Florida, except for citrus, zinc deficiency is most
often seen on orange-jessamine, loquat, wax-leaf privet, surinam
cherry, carambola, barbados cherry, and silk-oak (Table 5).
In Florida zinc deficiency of pecans and black walnut is
called rosette; of peaches and pears, little-leaf; of tung, bronz-
ing; and of citrus, frenching. However, each of these is only one
symptom of the zinc deficiency symptom complex. Species of
Table 5. Woody ornamental species in Florida on which zinc
deficiency has been identified experimentally or is suspected as
Botanical name Common name
Zinc deficiency identified experimentally
A leurites fordi Tung tree
A leurites montana Mu-oil tree
Carya illinoensis Pecan
Catalpa longissima Haiti catalpa
Citrus spp. Citrus species and varieties
Diospyros discolor Velvet apple
Diospyros kaki Oriental persimmon
Eribotrya japonica Loquat
Eugenia uniflora Surinam cherry
Grevillea robusta Silk-oak
Ilex rotunda Japanese holly
Juglans nigra Black walnut
Ligustrum japonicum Wax-leaf privet
Malpighia glabra Barbados cherry
Murraya paniculata Orange-jessamine
Persea americana Avocado
Prunus persica Peach
Prunus salicina Plum
Pyrus pyrifolia Pear
Ulmus americana American elm
Zinc deficiency suspected as cause
Cornus florida Dogwood
Liquidambar straciflua Sweet gum
Nerium oleander Oleander
Ulmus parviflora Chinese elm
Ulmus pumila Dwarf Asiatic elm
woody ornamentals vary in susceptibility to zinc deficiency;
species showing symptoms were observed growing in the same
area with other species which do not.
Zinc deficiency occurs on acid and calcareous soils in Florida.
Acid, sandy, and clay soils have in many locations been depleted
of their zinc supply by previous cropping, cumulative effects of
acid residue fertilizers, and to some extent by leaching. Alkaline
soils (over-limed acid soils, alkaline sands, and marl soils) and
soils high in phosphatic materials fix zinc in unavailable forms,
and this problem is further intensified on calcareous soils low in
native zinc content. Camp and Fudge (6) stated that zinc de-
ficiency of citrus in Florida was commonly associated with
over-liming and that zinc deficiency increased in amount and
severity when citrus was grown on soils of pH above 6.0. How-
ever, orange-jessamine, loquat, pecans, peaches, pears, etc., are
apparently less sensitive than citrus to pH conditions.
Figure 11.-Normal (left) and zinc-deficient peach shoots
showing chlorosis, crinkled leaves, wavy margins, and reduction
in leaf size.
Interveinal chlorosis on terminal leaves of growing shoots is
a characteristic foliage symptom of zinc deficiency. The midrib
and main lateral veins with some tissue bordering them remain
green, and intensity of yellowing is quite variable depending
on plant species, relative severity, and duration of the deficiency
(Fig. 11). As zinc deficiency increases in severity, leaves are
reduced in size to only 5% of normal in severe cases, and they
become very narrow and pointed on several species. This drastic
reduction in leaf size has led to the term little-leaf for this char-
acteristic zinc deficiency symptom on certain plants. Leaves of
some zinc-deficient plants are smooth (orange-jessamine, citrus,
etc.), while others develop crinkled leaves with wavy margins.
Severely affected tung leaves may have one-half of the leaf
smaller than the other. Mild chlorosis produced by zinc de-
ficiency is often indistinguishable from that of manganese and
iron, but the development of other symptoms of the zinc de-
ficiency complex will assist in its identification. Some peach
leaves show red to purple discolorations in chlorotic areas, and
zinc deficiency of tung has bronzing of leaves as a striking symp-
tom. In advanced stages, dead areas-irregular in extent, out-
line, and location-appear on leaves of some affected species
(loquat, peach, tung, etc.) (Fig. 12A, B) but not on the leaves
of some others.
Mild stages of zinc deficiency may not affect shoot growth,
but as the deficiency becomes more acute, internode length is
greatly reduced. When these affected shoots resume growth,
they produce compact clusters or tufts of abnormally small,
pointed leaves and shoots called rosette (orange-jessamine, pecan,
black walnut, peach, pear, plum, tung, etc.) (Fig. 13). Rosette
and little-leaf symptoms of zinc deficiency commonly appear first
on upper branches of affected plants, but later the entire plant
may become partially or entirely defoliated (pecan, citrus), and
shoots and branches may die back so that the plant may actually
decrease in size, and in advanced stages may die. Zinc deficient
plants are more susceptible to cold injury, and may be badly
injured or killed by winter temperatures that will not injure
nearby healthy plants.
Zinc deficiency of fruit trees (listed above) in north and
northwestern Florida has been corrected by soil or foliage ap-
plications of zinc, but soil application is the more desirable
method because of long lasting effects and ease of application.
Amount of zinc needed to prevent or correct the deficiency
varies with soil pH and type, age and size of affected plants,
and severity of the deficiency. Soil applications of 1 to 2 ounces
per tree to young peach, pear, plum, loquat, and satsuma orange
and 3 to 4 ounces per tree to young pecan and black walnut trees
will usually prevent or correct the deficiency. Larger plants may
require from 1/2 to 1 pound per plant of zinc sulfate. Zinc de-
ficiency of mature pecans and black walnut trees growing on
sandy soils can usually be corrected by applying 21/2 pounds per
tree of zinc sulfate, but on the heavier-textured sandy loam and
clay soils 5 to 10 pounds per tree of zinc sulfate may be required
(59). Soil applications of zinc should be made by broadcasting
it evenly under spread of the branches. Zinc should be applied
in spring or early summer to most woody ornamentals as they
respond the same season zinc is applied. Plants that do not re-
spond properly should be retreated the following season. Once
zinc deficiency has been corrected, additional applications should
be made only when the deficiency recurs.
Because zinc moves downward very slowly from surface ap-
plications, mixing it with the soil where possible before or after
planting is a desirable practice. Better response to zinc was ob-
tained when zinc sulfate was applied around established trees
and plowed in than from broadcast applications (61). One ounce
of zinc sulfate applied on the bottom and sides of the hole before
planting was as effective or more so than 4 ounces broadcast
on the soil surface after trees were planted (48).
A zinc-lime spray should be used when it is more convenient
to spray or when satisfactory response is not obtained (penin-
sular Florida) from soil applications.
Apply 3 pounds of zinc sulfate plus 1.2 pound of hydrated
lime in 100 gallons of water (1 ounce of zinc sulfate plus 1/3
ounce of hydrated lime in 2 gallons of water-see Table 8) in
spring or early summer. Repeat this application in subsequent
years as needed to correct the deficiency. This recommendation
is based on experimental information that, in peninsular Florida,
soil applications of zinc have not been consistently successful in
correcting zinc deficiency. Experimental information, excepting
Figure 12A.-Severe zinc deficiency symptoms of orange-jessa-
mine (Murraya paniculata) showing chlorosis, rosette, dwarfing
of leaves and shoots, and necrosis.
Figure 12B.-Severe zinc deficiency symptoms of loquat (Erio-
botrya japonica) showing chlorosis, reduction in leaf size, and
Figure 13.-Pear shoots (left) showing acute zinc deficiency
symptoms--chlorosis, little-leaf, rosette; (right) normal shoot.
citrus, is limited as to the response that can be expected from
soil applications of zinc to other zinc susceptible woody species
in this area (Table 5).
Copper deficiency was once widespread in Florida's com-
mercial citrus plantings and in commercial tung plantings that
once existed in northern peninsular Florida. It would therefore
be expected to occur on several other woody ornamental plants
in these areas, but it is not commonly found. Only a few species
of ornamental plants (common camellia, furry jasmine, Jasmi-
num nitidum, wax-leaf privet, Japanese pittosporum, Southern
Indian azalea, and rose) in peninsular Florida have shown mild
to moderate copper deficiency (Table 6).
Woody ornamentals in Florida on which copper deficiency
has been identified or is suspected are given in Table 6, and fur-
ther observation and experimentation should expand this list.
There is a difference in susceptibility of woody ornamentals to
copper deficiency; tung and species or varieties of citrus devel-
oped copper deficiency over the same area where many other
species showed no symptoms.
Dieback and exanthema are common names used for copper
deficiency on several species, but each is descriptive of only one
symptom of the copper deficiency symptom complex.
Table 6. Woody ornamental species in Florida on which copper
deficiency has been identified experimentally or is suspected as
Botanical name Common name
Copper deficiency identified experimentally
Aleurites fordi Tung tree
Camellia japonica Common camellia
Citrus spp. Citrus species and varieties
Jasminum multiflorum Furry jasmine
Jasminum nitidum Jasmine
Ligustrum japonicum Wax-leaf privet
Pittosporum tobira Japanese pittosporum
Rhododendron simsi Southern Indian azaleas
Rosa spp. Rose cultivars
Copper deficiency suspected as cause
Brassaia actinophylla Scheffelera
Coccolobis uvifera Sea-grape
Conocarpus erectus Silver buttonwood
Diospyros kaki Oriental persimmon
Hibiscus rosa-sinensis Chinese hibiscus
Jasminum mesnyi Primrose jasmine
Podocarpus macrophylla maki Yew podocarpus
Rhodoleia champion Hong-Kong tree
Viburnum odoratissimum Sweet viburnum
Viburnum suspensum Sandankwa viburnum
Copper deficiency occurs on acid and alkaline soils in Florida.
Organic soils (muck and peat) especially and light, sandy acid
soils are generally low in copper. Alkaline soils (over-limed acid
soils, alkaline sands, and marl soils) and soils high in phosphatic
materials reduce the availability of copper; thus correction of
copper and zinc deficiencies is more difficult under these soil con-
ditions. Copper deficiency has not been observed on susceptible
species such as tung on the clay soils (Red Bay, Ruston, Norfolk,
Greenville, Tifton, and related series) of northwestern Florida,
nor has it been seen on other woody ornamentals growing on
these clay soils in this area. Application of growth stimulating
fertilizers such as nitrogen may induce copper deficiency or ag-
gravate the existing deficiency (18, 38).
Leaves at tips of growing shoots are smaller than normal
leaves in mild stages, and in some cases an interveinal chlorosis
develops (furry jasmine, Jasminum nitidum, Japanese pitto-
sporum, 'Formosa' azalea). In other cases leaves are an over-all
lighter green color (wax-leaf privet, common camellia, 'Fielder's
White' and 'George Lindley Taber' azaleas). Leaves become
slightly to moderately "cupped" depending on species (furry
jasmine, Jasminum nitidum, 'Formosa' azalea, wax-leaf privet,
tung) or variously roughened and wrinkled (common camellia,
wax-leaf privet), and some affected leaves show a mild tip and
marginal burn. Leaves are much reduced in size in acute stages
and become strongly "cupped" and/or roughened and wrinkled,
and leaves of some species become thickened, leathery, and brit-
tle (common camellia, wax-leaf privet). Severe tip and margi-
nal burn is evident on young leaves of some species soon after
they unfold from the growing shoots. This produces irregular
broken margins of some species (common camellia, 'Formosa'
and 'Fielder's White' azaleas, tung). Premature leaf drop fre-
quently occurs, especially at shoot terminals.
Shoot growth is much reduced on severely affected plants
caused by a reduction in number and length of internodes, and
growing tips of some defoliated terminal shoots may dieback in
varying degrees. Multiple buds may develop (furry jasmine,
Jasminum nitidum, wax-leaf privet, citrus, tung) on acutely af-
fected plants, and they sometimes produce shoots, but the result-
ing small, slender twigs soon die. Growth is retarded in varying
Figure 14.-Copper-deficient (A) and normal (B) plants of
'Formosa' azalea. Plant (A) shows typical symptoms of copper
deficiency-chlorosis, small terminal leaves, tip burn, and dwarf-
degree, and acutely affected plants are severely stunted as com-
pared with similar plants receiving sufficient copper. Several
symptoms of the copper deficiency symptom complex are shown
in Figure 14. Copper deficiency increases the susceptibility of
affected plants to cold injury.
Copper deficiency of woody ornamental plants in Florida can
be prevented or corrected by soil or foliage applications of cop-
per. Soil treatment is generally effective, and is the best method
because of application ease and residual effect. Copper spray is
effective and quick in correcting copper deficiency and is a valu-
Most applied copper, unless mechanically mixed deeper into
the soil, is held in the topsoil, which delays response to soil
applications. Copper in small amounts is necessary for normal
plant growth, but excess copper in the soil retards growth by
injuring the root system, inducing a deficiency of one or more
other essential elements, especially iron. Injury to root system
of citrus by excess copper (53, 54) has induced iron deficiency
in Florida. Since copper accumulates in the topsoil, it will build
up to toxic levels if too much is applied. Up to 50 pounds of total
copper per acre (about 200 pounds per acre of copper sulfate
containing 25% copper) is adequate to prevent or correct copper
deficiency, and amounts above this level may depress growth.
Amount of copper to apply varies with age, size, variety and
species of plant, soil type and pH, severity of the disorder, and
method of application. In tests 1/6 ounce of copper sulfate in
3/4 pint of water applied to soil near base of 1-year-old trees
was as effective in correcting copper deficiency as broadcast soil
applications of 1, 2 and 3 ounces of copper sulfate per tree. Since
this treatment method was effective for tung, it may be appli-
cable to other woody ornamentals in Florida (29, 30).
Amount of copper sulfate to apply at the rate of 200 pounds
per acre to areas of various sizes and shapes are given in Table
7. Copper sulfate should be mixed into the top 6 to 8 inches of
soil before planting where possible, but it can also be applied to
plants established in the landscape. This can be done for small
areas by mixing the small amounts of copper sulfate recom-
mended in Table 7 in 1 to 2 handfuls to 1 quart or more of coarse
sand, depending on area size, or by dissolving it in 1 pint of
water and spreading evenly over the area to be treated. For large
areas dissolve copper sulfate in 5 to 100 gallons of water, de-
pending on size of area, and spray evenly over area to be treated.
Fertilizers containing copper can also be used to supply the
needed copper. Soil applications of copper may be made at any
time during the year.
Copper sprays are a desirable method of control under con-
ditions where immediate correction of copper deficient plants
is desired, a fungicidal spray is needed, or a delayed response to
soil applications of copper has occurred. Basic (neutral) cop-
per sulfate at rate of 3 pounds in 100 gallons of water (1 ounce
in 2 gallons of water) or a 3-1-100 copper-lime spray (1 ounce
of copper sulfate, 1/% ounce of hydrated lime in 2 gallons of water
-see Table 8) will correct copper deficiency of woody orna-
mental plants. Basic (neutral) copper sulfate spray is more de-
sirable for use on woody ornamentals because it is easier to mix
and leaves less unsightly residue than the copper-lime spray.
Best response is usually obtained from foliage sprays made any
time from early spring to mid-summer.
Table 7. Amounts of copper sulfate to apply to soil areas of
varying sizes and shapes, at rate of 200 pounds per acre.
Diameter Area in Amount of copper sulfate to apply
sq. ft. Grams Ounces Teaspoons
1 foot 0.8 1.6 0.06 1/4
11/ foot 1.8 3.7 0.13 '/
2 feet 3.1 6.5 0.23 3
22 feet 4.9 10.2 0.36 1/4
3 feet 7.1 16.0 0.56 2
3% feet 9.6 20.0 0.70 2%
4 feet 12.6 26.1 0.92 3%
41 feet 15.9 33.1 1.17 4
5 feet 19.6 40.8 1.49 5
Square or rectangular areas
1 2.1 0.07 1/
5 10.4 0.37 11/
10 20.8 0.74 2%
100 208.0 7.34 26
1000 2080.0 73.38
Table 8. Pounds and/or ounces of copper, zinc, and man-
ganese sulfates; borax, ammonium molybdate; and hydrated lime
to make 100 gallons of copper-zinc-manganese-boron-molyb-
Chemical2 (Ibs. or ozs.) Remarks
Copper sulfate 3.0 Ibs. First dissolve sulfates of cop-
Zinc sulfate 3.0 Ibs. per, zinc, and manganese;
Manganese sulfate 3.0 Ibs. borax; and ammonium molyb-
Borax 11.0 ozs. date by slowly dusting them
Ammonium molybdate 2.0 ozs. into spray tank, then add hy-
Hydrated lime 3.0 Ibs. drated lime and suitable
spreader. Apply spray to cover
all parts of the plant.
1Adapted, in part from Table 2, Fla. Agr. Exp. Sta. Bul. 536B, 1964,
Recommended fertilizers and nutritional sprays for citrus.
2Use 1.6 pounds of hydrated lime for each 3 pounds of copper sulfate,
1.2 pounds hydrated lime for each 3.0 pounds of zinc sulfate, and 0.2
pound of hydrated lime for each 3.0 pounds of manganese sulfate. No
lime is required if neutral zinc, copper, or manganese compounds are
Molybdenum deficiency of woody ornamental plants in Flori-
da has been identified only on varieties of Chinese hibiscus
(Hibiscus rosa-sinensis) and citrus. This deficiency is likely to
appear when varieties of Chinese hibiscus are grown on unlimed
acid sandy soils (pH 5.2 or lower) and is much less prevalent
on plants growing in calcareous soils. Symptoms have been ob-
served in the Gainesville area on a few Chinese-box orange
plants (Severinia buxifolia), a citrus relative, similar to those
described and illustrated (9) for citrus. Also, symptoms similar
to those of molybdenum deficiency on Chinese hibiscus have been
observed on Southern Indian azalea and wax-leaf privet in the
Palatka area; dogwood (Comus florida), loquat (Eriobotrya
japonica), and red myrtle (Myrica rubra) in the Gainesville
area; and turk's cap (Malvaviscus arboreus) elsewhere in the
state. Positive identification of these disorders has yet to be
There is a big difference in susceptibility to molybdenum
deficiency because, of the many different kinds of ornamental
plants grown in Florida, it has been identified only on Chinese
hibiscus and citrus.
Molybdenum deficiency of Chinese hibiscus is called "strap-
leaf", and of citrus "yellow spot" disease. Each of these again
is only one symptom of the molybdenum deficiency symptom
Factors affecting availability of molybdenum, except pH, are
not well known, but experience has shown that liming acid soils
may increase availability of molybdenum. This explains why
molybdenum deficiency of Chinese hibiscus is more prevalent on
acid sandy soils than on calcareous coastal soils in Florida.
Molybdenum deficiency symptoms and 2,4-D injury to Chi-
nese hibiscus foliage are very similar in appearance. This de-
ficiency develops on young leaves and shoots of many plants, but
citrus is an exception in that symptoms appear on the mature
In mild stages leaves at tips of growing shoots are slightly
reduced in size and misshapen as compared with normal leaves.
Acutely affected leaves are greatly reduced in size, but actually
there is a much greater reduction in width than length, produc-
ing the characteristic strap-like appearance (Fig. 15). Normal
leaf blades are thin, smooth, and pliant, whereas affected leaves
are rough, thick and leathery, with margins irregularly wrinkled
or buckled. In some leaves the margins are rolled downward.
Midrib and main veins of affected leaves are enlarged and more
prominent than those of normal leaves. A mild chlorosis is evi-
dent on some young developing leaves, but affected mature leaves
Figure 15.-Shoots of Chinese hibiscus, variety 'Brilliantis-
simus' (Single Scarlet). Left, normal; right, typical molybdenum
deficiency symptoms-strap-leaf; dwarfed, thick leaves with ir-
regular wrinkled or buckled margins; and prominent midribs and
are usually normal green. Depending on severity of molybdenum
deficiency symptoms, part or all of a plant's foliage may show
strap-leaf. Growth of severely affected shoots may be materially
retarded because of a reduction in length of internodes. Flower-
ing is greatly reduced on acutely affected plants, and individual
flowers are much reduced in size. Petals of some severely af-
fected flowers may fuse to form a solid funnel-shaped flower on
single flowered varieties.
Molybdenum deficiency is much more prevalent on acid
sandy soils (pH 5.0 and lower), and adjusting pH (Table 2)
to a range of 5.5 to 6.5 has largely eliminated this deficiency from
Florida's commercial citrus plantings (9) by increasing molyb-
denum availability. Therefore, this practice should have a similar
effect on Chinese hibiscus.
A combination spray and soil drench of sodium molybdate
is more effective in correcting molybdenum deficiency of Chinese
hibiscus (70) than either method alone. Apply at rate of 1 ounce
of sodium molybdate in 100 gallons of water (for smaller quan-
tities of spray use 1/4 teaspoon of sodium molybdate to 2 gallons
of water). Home owners and commercial spraymen should first
spray plants, then drench surrounding soil with the remaining
solution. Applying 1 pound of hydrated lime per plant along
with the molybdenum increased the residual effects (70). Spray
and spray plus soil drench treatments are usually effective for
1 year or longer in some cases. Treatments should be repeated if
symptoms reappear in subsequent years.
Sodium molybdate is compatible with other chemicals used
in a micronutrient spray (Table 8).
Boron deficiency of woody ornamentals in Florida has been
experimentally identified only on citrus, but is of minor im-
portance when citrus is grown in landscape plantings. Reports
have been received, first in 1946 and at intervals later, that old
coconut palms (Cocos nucifera) which had previously fruited
for many years were dropping all or nearly all of their fruit
and that no fruit matured on some of these trees. Boron de-
ficiency was suspected as a possible cause of the disorder. Though
experimental proof of this is still lacking, observations and
demonstrations indicate this problem of fruit set and maturation
of the coconut fruit in Florida may be caused by boron deficiency.
Boron deficiency occurs in Florida on citrus and possibly the
coconut palm, but has not been identified on other woody orna-
mentals growing in the state. This indicates a big difference be-
tween species in susceptibility to boron deficiency.
Florida soils are generally low in boron yet boron deficiency,
except for citrus, has not been a problem in growing woody orna-
mentals possibly because very small amounts of boron are needed
for normal plant growth. Boron is soluble in acid soils, and is
readily leached from them. It is fixed in unavalaible forms in
alkaline soils, thus it is surprising this deficiency is not common
on localized over-limdd acid sandy soils and the alkaline sands
and marl soils of Florida's coastal areas.
Boron deficiency first appears on young growing tissue
(leaves, shoots, fruit, inflorescence, roots). A well defined leaf
chlorosis is present on some species but absent on others. When
present, young leaves may show chlorosis at their tips and mar-
gins or may evidence interveinal chlorosis. Leaves on affected
shoots are small, leathery, and variously malformed (cupped,
wrinkled, and thickened).
Affected parts may become stiff and/or brittle, and cracking
may occur. Affected shoots are shortened, become abnormally
thick and stiff, and may dieback from the tips in varying de-
grees. Shoots with shortened internodes produce a rosette effect
when buds grow. A characteristic symptom on several plants is
discoloration and death of vascular tissue followed by cracking
and splitting because of later growth stress. Frequently terminal
growth dies, flowers blast, and fruit and seeds fail to develop,
because boron deficiency affects the growing tissue. Boron de-
ficiency develops to a much greater degree on susceptible species
during periods of prolonged drought.
In mild stages fruit set is reduced, and some fruit may drop
throughout the fruit's maturation period. As boron deficiency
becomes chronic and severe, all stages of the deficiency appear,
and they may vary from reduced fruit setting and subsequent
dropping to cases where there is little or no fruit set. In advance
stages the central stem and main side branches of the inflor-
escences blacken and dieback and flowers blast. In chronic and
acute cases, previously fruitful palms may drop all or nearly all
of their fruit. A characteristic browning and death of areas of
the husk indefinite in location, extent, and outline are produced
on affected fruit. As affected tissue dies and dries out, cracking
and splitting of the husk occurs, and an amber-colored gum
exudes from the cracked areas. Severely affected fruit may not
produce a shell. No leaf symptoms have been associated with
this deficiency in Florida.
Woody ornamental species showing deficiency symptoms
similar to those described above which have not responded to
spray and/or soil applications of zinc, manganese, copper, iron,
molybdenum (see section on multiple deficiencies), or any of the
macronutrients could have boron deficiency. Spray such plants
in the spring or early summer with 2/3 pound of borax in 100
gallons of water (1/5 ounce of borax in 2 gallons of water).
Borax is compatible with other chemicals used in micronutrient
These treatments are suggested for coconut palms showing
symptoms similar to those described above. Dissolve 1/ teaspoon
of borax in 1 gallon of water and pour from 1 to 2 quarts of
this liquid into the bud where possible. Apply borax to soil at
rate of 2 to 4 ounces per mature palm in February or March
and again in July. Continue these yearly applications until af-
fected palms again mature fruit.
When two or more elements are deficient at the same time,
all deficient elements must be applied before affected plants will
respond completely to treatment. The multiple deficiency prob-
lem has been encountered in Florida with several woody plants
where several deficiency combinatigris (various combinations of
copper, zinc, magnesium, iron, and manganese deficiencies) were
simultaneously affecting growth and yield. Such conditions have
been observed with woody ornamental species growing on cal-
careous soils of the coastal areas, especially on the lower east
coast. In these areas this is an important factor affecting growth,
vigor, and the subsequent ornamental value of affected plants.
Deficiencies of this type are some times called marl or lime
chlorosis; chlorosis is a prominent symptom, but is only one
symptom of the multiple deficiency complex.
Multiple deficiencies are caused by various combinations of
several causal factors previously given for individual elements
involved in a given multiple deficiency combination. For example,
an element or elements may be naturally low in the soil, may
have been lost by leaching or cropping, or may have been fixed
in a relatively unavailable form in calcareous soils.
Chlorosis is a characteristic foliage symptom of the multiple
deficiency symptom complex. In early stages terminal leaves of
shoots show an interveinal chlorosis, but as the deficiencies be-
Figure 16.-Multiple deficiency symptoms chlorosiss, reduction
in leaf size, and necrosis) on Bengal clock-vine (Thunbergia grandi-
flora) growing on calcareous soil of lower east coast.
come chronic and acute all leaves of a plant may be affected and
become yellow to ivory with little or no green color remaining
(Fig. 16.). Intensity of yellowing varies with species and sever-
ity of deficiencies. Leaves are reduced in size, internodes are
shortened, and growth of severely affected plants is materially
reduced. This continues until the deficiencies are corrected. Pre-
mature leaf drop and dieback of terminal shoots may occur, the
amount varying with severity of the casual deficiencies, species
affected, and degree of adverse weather conditions such as tem-
perature and drought.
Multiple deficiencies frequently have the overall appearance
of iron and/or manganese deficiencies, but often application of
only iron or manganese will not correct the disorder. Sometimes
symptoms of one deficiency mask those of one or more other de-
ficiencies, and symptoms of the masked deficiencies appear when
the dominant deficiency is corrected. For example, zinc deficiency
of tung masked those of copper and manganese in the Gaines-
ville area, and they appeared only after zinc deficiency had been
Multiple deficiencies occur on woody ornamentals in Florida
growing on both acid and calcareous soils (alkaline sands and
marl soils), but they are much more prevalent and difficult to
correct on alkaline soils (pH 7.0 and above) of coastal areas,
particularly those of the lower east coast. Alkaline soils reduce
availability of the nutrient elements manganese, iron, zinc, cop-
per, boron, magnesium, and phosphorous, which are fixed under
these soil conditions. Treatments such as incorporating organic
matter in the soil, mulching, and use of soil acidifying chemicals
(see iron deficiency section) are desirable.
Satisfactory response to soil applications of manganese, iron,
copper, zinc in certain areas, boron, molybdenum, and mag-
nesium has been obtained with these deficiencies on plants grow-
ing on acid soils in Florida. Zinc applied to the soil has corrected
zinc deficiency on acid soils in northern peninsular and north-
western Florida on pecan, tung, satsuma, peach, pear, plum,
oriental persimmon, loquat, and black walnut, but has generally
been unsuccessful on acid soils of peninsular central and
southern Florida and on calcareous soils statewide. Commercial
"shot gun" mixtures of these elements should be used according
to the manufacturers directions. When all are applied together
by the home owner or commercial operator, elements should be
applied at the minimum rates recommended in the sections on
manganese, iron, zinc, copper, boron, molybdenum, and mag-
nesium deficiencies. Use zinc sprays in areas and under soil
conditions in Florida where zinc soil applications are ineffective.
Directions for making this spray are given in the zinc deficiency
section. Control iron deficiency on acid soils by soil applications
of iron chelate of ethylene diamine tetraacetic acid (FeEDTA).
Usually one application of these materials per year in late
winter or early spring is sufficient, but repeat treatments yearly,
except copper, until symptoms disappear, then stop treatment.
Under such soil conditions (pH of 7.0 and above), where
multiple deficiencies are more likely to occur, nutritional sprays
are frequently the best control method. Use "shot gun" nutri-
tional sprays according to manufacturer's directions. Users can
make their own "shot gun" nutritional sprays, however, and
directions for doing this are given in Table 8. Because of pre-
viously mentioned factors that limit successful use of iron sprays,
iron chelates that are effective on alkaline soils should be used,
and they are discussed in the section on iron deficiency.
Usually one nutritional spray a year applied in the spring is
sufficient, but sometimes two or three applications during the
growing season are required for control.
SYMPTOMS OFTEN CONFUSED WITH THOSE
Several toxic and infectious agents injure plants causing
symptoms which may resemble those produced by nutritional
deficiencies. Thus, it is desirable to know what treatments (fer-
tilizers, herbicides, insecticides, fungicides, nematocides, salt
content of irrigation water, etc.) have been a;llli1't- previously
which might have affected plants and prol.bi.nm .lin i..-ing.
Salt (sodium chloride) in high concentrations whether from
salt spray, irrigation water, or absorbed from the soil will in jur.
plants. Degree of injury varies depending on plant species, salt
concentration, and application method (whether from soil or a
spray). Symptoms vary from irregular chlorotic areas to necro-
sis which ranges from small dead spots to include all or nearly
Figure 17.-Boron toxicity on Viburnum suspensum showing
marginal leaf scorch and areas of dead tissue extending inward
from the margins between main veins. The boron came from
cleanser used in a clothes washer.
*~~; ;IJ- ..~~~'
all of the leaf, defoliation, and ultimate death of plants. Similar
symptoms are produced when chemical salts used in fertilizers,
especially inorganic salts supplying nitrogen and potassium, are
applied in high amounts.
Boron in toxic concentrations, usually from certain house-
hold cleansers and detergents in wash water, caused marginal
leaf scorch followed by dead tissue extending inward between
main veins from dead margins (Fig. 17). In severe cases af-
fected plants may be defoliated.
Fungicides, insecticides, and nematocides applied in toxic
concentrations will injure plants, causing chlorosis, necrosis, and
reduction in growth similar to many nutritional deficiencies.
High amounts of herbicides produce various symptom pat-
terns, but they are usually evidenced as reduced growth, chloro-
sis, and varying degrees of necrosis. On certain plants (Chinese
hibiscus, roses) injury by 2,4-D is similar to that described for
molybdenum deficiency of hibiscus.
Infection by fungi, bacteria, and algae produce a variety of
leaf patterns on susceptible species usually evidenced as chlorosis
in localized spots and/or necrotic spots. Virus infections pro-
duce variable symptoms which also include chlorosis, mottling,
distortion, dwarfing and necrotic spotting, depending on the
virus and plant species attacked. Attack by certain insects
(aphids, bud mites, etc.) causes small and misshaped leaves on
some species. Lack of water may materially reduce leaf size and
cause symptoms common to other problems.
The following references contain information of value to the
many people involved in planting, maintenance, and care of woody
ornamentals growing in Florida's landscape plantings, particularly
as related to identification and correction of nutrient dificiencies.
1. Barnette, R.M. and H. Mowry. 1936. Soil reaction and azalea
growth. Soil Sci. 41 (1): 71-78.
2. Barnette, R.M. and H. Mowry. 1936. Soils for azaleas. Fla.
Agr. Exp. Sta. Press Bul. 496.
3. Barrows, H.L., M.F. Neff, N. Gammon, Jr., and W.W. Kilby.
1960. Response of one-year-old tung trees to levels and place-
ments of zinc sulfate as affected by soil type. Proc. Amer. Soc.
Hort. Sci. 76: 300-309.
4. Blackmon, G.H., R.D. Dickey, and R.J. Wilmot. 1942. Variety
tests of minor fruits and ornamentals. Ann. Rept. Fla. Agr.
Exp. Sta. pp. 82-83.
5. Bryan, O.C. 1957. Malnutrition symptoms of citrus. Sta. Fla.
Dept. Agr. Bul. 93.
6. Camp, A.F. and B.R. Fudge. 1939. Some symptoms of citrus
malnutrition. Fla. Agr. Exp. Sta. Bul. 335.
7. Camp, A.F. and M. Peech. 1938. Manganese deficiency in cit-
rus in Florida. Proc. Amer. Soc. Hort. Sci. 68:195-200.
8. Childers, N.F. Editor. 1966. Nutrition of fruit crops-
Second Edition. Somerset Press, Inc., Somerville, N.J.
9. Citrus Experiment Station. 1958. Florida guide to citrus
insects, diseases and nutritional disorders in color. Agr. Exp.
Sta., Gainesville, Florida.
10. Dickey, R.D. 1938. Testing of native and introduced shrubs
and ornamentals and methods for their propagation. Fla. Agr.
Exp. Sta. Ann. Rept. pp. 92-93.
11. Dickey, R.D. 1942. Manganese deficiency of palms in Flori-
da. Fla. Agr. Exp. Sta. Press Bul. 576.
12. Dickey, R.D. 1942. A preliminary report on iron deficiency of
tung in Florida. Fla. Agr. Exp. Sta. Bul. 381.
13. Dickey, R.D. 1945. A manganese deficiency of palms and
some other ornamental trees in Florida. Proc. Twenty-first
Nat'l. Shade Tree Conf. 98-103.
14. Dickey, R.D. 1947. Deficiencies in ornamentals. Proc. Fla.
Sta. Hort. Soc. 60:199-203.
15. Dickey, 1951. The lime requirements of ornamentals. Proc.
Soil Sci. Soc. Fla. 11:94-96.
16. Dickey, R.D. 1965. Azalea culture. Fla. Agr. Exp. Sta. Cir.
17. Dickey, R.D. 1965. Copper deficiency of some container grown
woody ornamental plants. Proc. Fla. Sta. Hort. Soc. 78:386-392.
18. Dickey, R.D. 1967. Factors affecting copper deficiency of
container grown Ligustrum japonicum. Proc. Fla. Sta. Hort.
19. Dickey, R. D. 1968. Growth and quality of woody ornamental
nursery stock. Ann. Rept. Fla. Agr. Exp. Sta. p. 102.
20. Dickey, R.D. 1969. Hibiscus in Florida. Fla. Agr. Ext. Ser.
21. Dickey, R.D. 1972. Identification and correction of copper
deficiency of Rhododendron simsi 'George Lindley Taber' cut-
tings. Proc. Fla. Sta. Hort. Soc. 85:398-400.
22. Dickey, R.D. 1974. Magnesium applications to woody orna-
mental plants in the Gainesville area. Unpublished data.
23. Dickey, R.D. and G.H. Blackmon. 1940. A preliminary report
on little-leaf of the peach in Florida-A zinc deficiency. Fla.
Agr. Exp. Sta. Bul. 344.
24. Dickey, R.D. and M. Drosdoff. 1943. Control of manganese
deficiency in a commercial tung orchard. Proc. Amer. Soc. Hort.
25. Dickey, R.D. and W. Reuther. 1938. Manganese sulfate as a
corrective for a chlorosis of certain ornamental plants. Fla.
Agr. Exp. Sta. Bul. 319.
26. Dickey, R.D. and R.J. Wilmot. 1939. Testing of native and
introduced shrubs and ornamentals and methods for their
propagation. Fla. Agr. Exp. Sta. Ann. Rept. p. 105.
27. Dickey, R.D. and R.J. Wilmot. 1941. Testing of native and in-
troduced shrubs and ornamentals and methods for their propa-
gation. Fla. Agr. Exp. Sta. Ann. Rept. pp. 80-81.
28. Dickey, R.D. and R.J. Wilmot. 1942. Testing of native and
introduced shrubs and ornamentals and methods for their
propagation. Fla. Agr. Exp. Sta. Ann. Rept. pp. 81-82.
29. Dickey, R.D., M. Drosdoff, and J. Hamilton. 1948. Copper
deficiency of tung in Florida. Fla. Agr. Exp. Sta. Bul. 447.
30. Drosdoff, M. and R.D. Dickey. 1943. Copper deficiency of
tung trees. Proc. Amer. Soc. Hort. Sci. 42:79-84.
31. Drosdoff, M. and A.L. Kenworthy. 1944. Magnesium deficien-
cy of tung trees. Proc. Amer. Soc. Hort. Sci. 44:1-7.
32. Drosdoff, M. and F.S. Lagassee. 1950. The effect of some
magnesium and calcium fertilizers in a magnesium deficient
bearing tung orchard. Proc. Amer. Soc. Hort. Sci. 56:5-11.
33. Drosdoff, M. and J.H. Painter. 1942. A chlorosis and necrosis
of tung leaves associated with low potassium content. Proc.
Amer. Soc. Hort. Sci. 41:45-51.
34. Embleton, T.W. and W.W. Jones. 1959. Correction of mag-
nesium deficiency of orange trees in California. Proc. Amer.
Soc. Hort. Sci. 74:280-288.
35. Floyd, B.F. 1917. Dieback or exanthema of citrus. Fla. Agr.
Exp. Sta. Bul. 140.
36. Fudge, B.R. 1939. Relation of magnesium deficiency in grape-
fruit leaves to yield and chemical composition. Fla. Agr. Exp.
Sta. Bul. 331.
37. Gammon, Jr., N. and R.H. Sharpe. 1956. Mouse ear-A man-
ganese deficiency of pecans. Proc. Amer. Soc. Hort. Sci. 68:
38. Hamilton, J. and S.G. Gilbert. 1947. The relation of fertiliza-
tion with copper and nitrogen to copper deficiency symptoms,
leaf composition and growth of tung. Proc. Amer. Soc. Hort.
39. Harkness, R.W. and J.L. Malcolm. 1957. Iron chlorosis in
avocado. Proc. Fla. Sta. Hort. Soc. 70:297-300.
40. Koo, R.C.J. and T.W. Young. 1969. Correcting magnesium
deficiency of limes grown on calcareous soils with magnesium
nitrate. Proc. Fla. Sta. Hort. Soc. 82:274-278.
41. Lawrence, F.P. 1967. Citrus for the dooryard. Fla. Agr. Ext.
Ser. Bul. 166B.
42. Leonard, C.D. and I. Stewart. 1953. Chelated iron as a cor-
rective for lime-induced chlorosis. Proc. Fla. Sta. Hort. Soc.
43. Leonard, C.D. and I. Stewart. 1953. An available source of
iron for plants. Proc. Amer. Soc. Hort. Sci. 62:103-110.
44. Lynch, S.J. 1943. Studies of minor fruits and ornamentals.
Fla. Agr. Exp. Sta. Ann. Rept. pp. 169-172.
45. Malcolm, J.L. 1953. Chelates for the correction of iron chlo-
rosis in sub-tropical plants. Proc. Fla. Sta. Hort. Soc. 66: 179-
46. Malo, S.E. 1966. Correction of iron chlorosis of avocados
growing in calcareous soils. Proc. Fla. Sta. Hort. Soc: 79:386-
47. Mowry, H. and A.F. Camp. 1934. A preliminary report on
zinc sulfate as a corrective for bronzing of tung trees. Fla. Agr.
Exp. Sta. Bul. 273.
48. Neff, M.F. and H.L. Barrows. 1957. Influence of level, source,
and placement of zinc applied to newly planted tung trees.
Proc. Amer. Soc. Hort. Sci. 69:176-182.
49. NeSmith, J. and E.W. McElwee. 1971. Soil reaction (pH) for
flowers, shrubs and lawn. Fla. Coop. Ext. Ser. Cir. 352.
50. Phillips, A.M., J. R. Large, and J.R. Cole. 1964. Insects
and diseases of the pecan in Florida. Fla. Agr. Exp. Sta. Bul.
51. Reitz, H.A., C.D. Leonard, I. Stewart, R.C.J. Koo, D. V. Calvert,
C.A. Anderson, P.F. Smith, and G.K. Rasmussen. 1964.
Recommended fertilizers and nutritional sprays for citrus. Fla.
Agr. Exp. Sta. Bul. 536B.
52. Reuther, W. and R.D. Dickey. 1937. A preliminary report on
frenching of tung trees. Fla. Agr. Exp. Sta. Bul. 318.
53. Reuther, W. and P.F. Smith. 1952. Chlorosis in Florida citrus
groves in relation to certain soil constituents. Proc. Fla. Sta.
Hort. Soc. 65:62-69.
54. Reuther, W. and P.F. Smith. 1954. Toxic effects of accumu-
lated copper in Florida soils. Proc. Fla. Soil Sci. Soc. 14:17-23.
55. Ruehle, G.D. 1941. Diseases of minor fruits and ornamentals.
Ann. Rept. Fla. Agr. Exp. Sta. pp. 195-196.
56. Ruehle, G.D. 1942. Diseases of minor fruits and ornamentals.
Ann. Rept. Fla. Agr. Exp. Sta. pp. 196-198.
57. Sharpe, R.H. 1966. Peaches and nectarines in Florida. Fla.
Agr. Exp. Sta. Cir. 299.
58. Sharpe, R.H. and N. Gammon, Jr. 1951. Magnesium deficiency
of pecans. Proc. SE Pecan Growers 44:23-28.
59. Sharpe, R.H. and N. Gammon, Jr. 1958. Pecan growing in
Florida. Fla. Agr. Exp. Sta. Bul. 601.
60. Smith, P.F. 1962. Mineral analysis of plant tissue. Ann. Rev.
Plant Physiol. 13:81-108.
61. Smith, P.F. and G.K. Rasmussen. 1959. Field trials on the
long-term effect of single applications of copper, zinc, and
manganese on Florida sandy citrus soil. Proc. Fla. Sta. Hort.
62. Stewart, I. and C.D. Leonard. 1952. Chelates as sources of
iron for plants growing in the field. Science 116:564-566.
63. Stewart, I. and C.D. Leonard. 1952. Iron chlorosis-Its pos-
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64. Volck, G.M. 1971. Fertilizers and fertilization. Fla. Coop.
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65. Volck, G.M. and C.E. Bell. 1944. Soil reaction (pH)-some
critical factors in its determination, control and significance.
Fla. Agr. Exp. Sta. Tech. Bul. 400.
66. Wallace, A. and O.R. Lunt. 1960. Iron chlorosis in horticul-
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67. Wallace, A., C.P. North, R.T. Muller, and N. Hermaiden. 1953.
Chelating agents as a means of supplying micronutrients to
woody plants in alkaline and calcareous soils. Proc. Amer. Soc.
Hort. Sci. 62:116-118.
68. West, S.H. and H.C. Harris. 1965. Physiological and bio-
chemical functions of micro-elements. Soil Crop Sci. Soc. Fla.
69. Westgate, P.J. 1952. Azalea tip burn. Florida Grower 60
70. Westgate, P.J. and H.N. Miller. 1955. Molybdenum deficiency
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71. Young, T.W. 1960. Response of iron chlorotic avocado trees
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Institute of Food and Afgrultural Sciences
7univrst of Floid