• TABLE OF CONTENTS
HIDE
 Copyright
 Front Cover
 Pruning principles
 Suggested practices
 Pruning equipment
 Brush disposal
 Conclusion
 Back Cover






Group Title: Florida Cooperative Extension Service circular 477
Title: Pruning principles and practices for Florida citrus
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00049271/00001
 Material Information
Title: Pruning principles and practices for Florida citrus
Series Title: Circular Florida Cooperative Extension Service
Physical Description: 23 p. : ill. ; 23 cm.
Language: English
Creator: Phillips, R. L ( Richard Lee ), 1928-
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1980?
 Subjects
Subject: Citrus fruits -- Pruning -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: R.L. Phillips.
General Note: Cover title.
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00049271
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 08851582

Table of Contents
    Copyright
        Copyright
    Front Cover
        Page 1
        Page 2
    Pruning principles
        Page 3
        Page 4
        Page 5
    Suggested practices
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
    Pruning equipment
        Page 21
    Brush disposal
        Page 22
    Conclusion
        Page 23
    Back Cover
        Page 24
Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




(i -'1


Circular 477


PRUNING PRINCIPLES

AND PRACTICES

FOR FLORIDA CITRUS


R. L. PHILLIPS
O F


Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
John T. Woeste, Dean for Extension


, 0C- C







PRUNING PRINCIPLES AND
PRACTICES FOR
FLORIDA CITRUS

R. L. Phillips


Proper control of vegetative growth is essential for maintaining
healthy, productive citrus groves. Most citrus groves in Florida must
be pruned eventually to avoid problems associated with overcrowded,
excessively tall trees. Crowded conditions result in poor light accessi-
bility, a loss of lower foliage, relocation of fruiting to the top of the
canopy, reductions in fruit yield and quality, poor spray coverage and
interference with cultural and harvesting operations. Excessively
tall trees are difficult to spray effectively and harvesting is more ex-
pensive. It is wise to prune before these problems appear.
The response of citrus trees to pruning depends on many factors,
such as tree vigor, age, fruiting habits, growing conditions and pro-
duction practices. The influence of a variety of variables make deci-
sions on proper pruning procedures difficult. These variables include
the type, degree, frequency and timing of pruning, the different vari-
eties of citrus of various ages at different spacings and the varying
conditions under which they are grown. No one system or set of rules
can be adequate for the variety of situations encountered in the field.
Selection of the proper pruning procedure for a given grove situation
will depend upon research results, grower observations, good sense
and an understanding of the principles involved.

PRUNING PRINCIPLES
Sunlight. The importance of adequate sunlight in the production
of high yields of good quality fruit cannot be overstressed. Light pro-
vides the energy for photosynthesis in which carbon dioxide from the
air and water from the soil are combined in the chloroplasts of the
leaves to form the basic foods upon which the trees live, grow and bear
fruit. Light becomes a limiting factor in crowded groves and pruning
is done to keep them open for better light access. For best results,
growers must adjust tree height, middle width and hedging angles so
that adequate light reaches a maximum amount of foliage. Sunlight
not only influences flowering and fruit set but also enhances fruit ma-
turity and color development.
Growth habit. Most citrus trees develop a desirable shape when
they are left to grow naturally (Fig. 1). Early branches tend to grow
upright, bending with their own weight to form laterals, then bend-



























Fig. 1. Natural shape of an uncrowded and unpruned orange tree.
Favorable light conditions are maintained on all sides of the
tree.

ing further with the additional weight of fruit to form skirts. New
branches sprout from the upper side of the laterals and become domi-
nant. These, in turn, droop and the process is repeated as the tree
grows. Branches in the upper parts of the tree tend to be more vigor-
ous because of this dominance and exposure to more sunlight, while
little vegetative growth occurs on the skirts. Hedged trees, therefore,
tend to grow more vigorously at the shoulders than at the skirts.
Apical dominance. Suppression of lateral bud growth by the ter-
minal bud is known as apical dominance. Apical dominance explains
many of the growth characteristics of trees and their responses to
pruning. Branching is influenced by an auxin produced in the termi-
nal bud which moves down the stem to inhibit lateral bud break. Re-
moval of the terminal bud destroys apical dominance so that one or
several lateral buds will commence to grow and branching results.
Vigorous shoots called water sprouts or suckers show extreme apical
dominance with no side-branch development. Apical dominance var-
ies somewhat with vigor and variety.
Basic pruning cuts. Heading back and thinning out are the main
types of pruning cuts and are used for somewhat opposite objectives.
Heading back removes the terminal portion of a shoot or branch, de-
stroying apical dominance and stimulating lateral bud breaks. This
tends to produce a more bushy, compact tree. Mechanical hedging







and topping are forms of mass heading back. Thinning out involves
the removal of complete branches to laterals or to the main trunk and
is done by selective pruning with hand-held equipment. It encour-
ages longer growth of the remaining terminals and can result in a
larger, more open tree. This type of pruning is sometimes done for
better light penetration into the tree.
Bearing habits. The balance between tree growth and fruitful-
ness appears to depend, to some extent, upon a relationship between
carbohydrates and nitrogenous compounds within the tree. When
both are adequate, moderate growth and high yields occur. When
both are low, citrus trees grow and fruit poorly. A tree low in carbohy-
drates and high in nitrogen tends to produce vigorous vegetative
growth at the expense of fruit production. Since carbohydrates are
manufactured and stored in the leaves, heavy pruning which re-
moves a large portion of the leaf area can result in this condition. Too
much nitrogen after severe pruning can aggravate the problem, caus-
ing thick peel and puffiness. Nitrogen applications should therefore
be adjusted to the severity of pruning. Some growers are reducing ni-
trogen applications in an effort to avoid an imbalance when heavy
pruning is done. Omitting a nitrogen application before heavy prun-
ing and possibly after will reduce both an expense and excessive vege-
tative growth. The length of time this limitation should continue will
depend upon the severity of pruning and the rate of top recovery.
Maintenance pruning should not affect fertilizer requirements.
Some citrus groves tend to have a bearing habit with alternating
high and low yields. A heavy crop of fruit tends to deplete carbohy-
drates and results in a small crop and increased vegetative growth
the following year. Pruning after a heavy crop increases this problem
because the carbohydrate supply has been somewhat depleted and
the capacity to produce carbohydrates has been reduced. Poor fruit
quality may also result from this practice. Pruning after a light crop
and before an expected heavy crop should help reduce alternate bear-
ing and produce much more satisfactory results.
The orientation of branches in space has a marked effect on growth
and fruiting. A decrease in growth rate and an increase in flowering
occurs when branches bend to a horizontal position. A possible expla-
nation for this phenomenon is a change in the distribution of growth
substances and carbohydrates. Favoring horizontal branches over
upright ones should result in better growth control and more fruit.
Relation between tree size and fruit area. Large trees with high
individual yields do not produce as much fruit for their size as do
small trees. Most citrus fruit is borne in an outside vegetative shell
about 3 ft. (0.9 m) thick where light is adequate for fruit bud forma-
tion. The area inside of this is occupied mainly by supporting struc-
ture and is mostly wasted space as far as fruit production is con-







cerned. Therefore, the proportion of fruit-producing foliage to sup-
porting structure becomes less as trees increase in size so that small
trees are more efficient units of production. However, a larger num-
ber of smaller trees in a given area does not necessarily contain more
foliage capable of bearing fruit because yield can be less if the trees
are lower than needed for adequate light conditions. Also, there are
more nonbearing middles per acre when rows are spaced close to-
gether. Theoretically, the greatest amount of fruit-bearing volume
per acre could be obtained with hedges about 6 ft. (1.8 m) thick since
the unfruitful framework would be largely eliminated and a solid
fruiting wall would be attained.
Responses to severe pruning. Severe pruning stimulates vigor-
ous new vegetative growth, especially when done before a major
growth flush. This happens because an undisturbed root system is
providing water and nutrients to a reduced bud area. The larger the
wood that is cut, the larger the subsequent shoot. Vegetative response
to pruning is greatest where the most severe cuts are made, resulting
in a strong tendency for pruned trees to resume their natural shape.
Effects of severe pruning on the fruit include increases in size and
juice content, decreases in soluble solids and acid and no change in
the soluble solids:acid ratio. This effect tends to diminish after the
first year.
Heavy pruning usually stimulates excessive vegetative growth at
the expense of fruiting wood. Heavy pruning of a severely crowded
grove typically results in a crop reduction the first year, recovery of
previous yield the second year and higher yields the third year, al-
though this can vary with conditions and the size of the previous crop.

SUGGESTED PRACTICES
Young trees. Severe pruning and training of young, non-bearing
trees tends to delay fruit production and should be avoided. Most
trees need no pruning for the first few years in the grove except for re-
moval of sprouts on the trunk (Fig. 2). These can be easily brushed off
when young and tender and the wounds will be small. Larger sprouts
should be cut off flush with the trunk. These wounds should be paint-
ed to avoid invasion by foot rot organisms. Sprouting on the trunks of
young trees can be greatly reduced by using a commercial sprout in-
hibitor containing naphthaleneacetic acid. Protective wraps around
the trunk also can reduce sprouting in addition to providing protec-
tion from sunburn, sandblasting and rodents. Occasionally, a vig-
orous sucker will dominate a weak tree or a sucker may arise from
the root-stock. These should be removed early, before they compete
too greatly with more desirable growth.













































Fig. 2. Sprouts on the trunk of a young orange tree. These are easily
removed at this stage or smaller and the wounds are small.

Pruning during the first few years of tree development should be
light so that it does not stimulate excessive vegetative growth and de-
lay fruit production. Selection of permanent scaffold branches during
the first few years is rarely successful since the natural growth habit
of these trees is so unpredictable. New growth may occur at unexpect-
ed places and become dominant over selected branches. When the

7








tree is 3 or 4 years old, depending on its growth, branches that are too
closely spaced or are crossed and entangled should be removed. This
pruning should be light, just sufficient to establish a desirable frame-
work without stimulating excessive vegetative growth. Pruning dur-
ing the next several years should be limited to removal of water
sprouts, dead wood and occasional branches which interfere with the
growth of scaffold limbs.
Mature trees. These require little pruning until the trees begin to
crowd. Water sprouts should be periodically removed from the trunk
and scaffold limbs since they are unproductive, compete for water and
nutrients, make satisfactory pest control difficult and are not desir-
able as permanent branches. Unwanted limbs should be removed to
their base or to a lateral to reduce sprouting of new buds in the area
around the cut. Sprouts which could be used to fill in a vacant space in
the tree periphery should be left. They will produce fruit when they
receive adequate light. Deadwood should be removed every 3 to 5
years, depending on the amount present and on the labor supply,
since it can scar fruit and be a source ofmelanose infection. This can
be done at any time when labor is plentiful. Growers need only to re-
move dead branches of /4 in. (0.64 cm) in diameter or larger since
smaller dead wood is often broken off in harvesting and other grove
operations. All cuts should be made into live wood, flush with a larger
branch or at a lateral
Hedging. When a grove is laid out, each tree is allotted a unit of
space in which to grow. When this space is exceeded, crowding occurs
and results in inadequate light conditions, losses of foliage and fruit
production in the lower portion of the tree, hindrance of cultural
and harvesting operations and interference with adequate spray
coverage.
Hedging, which consists of cutting back the sides of trees to prevent
or alleviate crowding, has become a common practice since the deve-
lopment of mechanical equipment for this purpose. Middles (alleys)
between tree rows should be sufficiently wide to accommodate orchard
equipment and to provide adequate light access to the sides of the
trees. Middles are usually hedged to a width of 7-8 ft. (2.1-3.1 m), but
this has varied from 6-9 ft. (1.8-2.7 m). Hedging facilitates orchard
operations, reduces damage to equipment and injury to operators,
trees and fruit and improves fruit set and color development.
Hedging should be started before crowding becomes a problem so
that only light cutting is necessary and little, if any, crop reduction
results. The closer the spacing and the more vigorous the trees, the
sooner hedging is required and the more frequently it needs to be
done. Removal of a large portion of the tree may be required when
pruning is deferred until severe crowding occurs. Excessive vegeta-








tive growth and a drastic reduction in subsequent yield may result.
Hedging of severely crowded groves aids in restoration of the tree
skirts and opens them up for passage of grove equipment. However,
heavy cutting is more expensive, an initial crop reduction can be ex-
pected and brush disposal is more troublesome and costly.
Hedging is usually done at an angle, with the boom tilted toward
the tree tops so that the middles are wider at the top than at the bot-
tom, allowing more light to reach the skirts of the tree. Hedging
angles being used vary from 2.5 to 25 degrees from vertical with in-
termediate angles of 10 to 15 degrees being more commonly used and
generally more satisfactory (Fig. 3). Greater hedging angles result in
longer exposure of the sides to sunlight and delayed overgrowth of the
skirts by the more vigorous shoulders of the trees. With wide angles,
topping can sometimes be done with one pass of the boom instead of
two or can be eliminated entirely if the trees come to a peak at a suit-
able height. Other advantages of hedging at wider angles may be bet-
ter spray coverage, particularly from the air, and more efficient har-
vesting since a higher percentage of the fruit is accessible to pickers
on the ground. Possible disadvantages of extreme angles are a
greater initial yield reduction when they are imposed on older trees,
greater stimulation of long, undesirable shoot growth and greater ex-
posure of fruit to possible cold injury. Although a greater initial yield
reduction may occur if considerable foliage is removed when a
greater hedging angle is first imposed, yields tend to differ little, if
any, between angles in subsequent years.
Many groves are cross hedged so that space is maintained between
trees in both directions. The desirability of hedging between trees
within the row (cross hedging) depends on a number of factors. Proba-
bly the most important of these are tree spacing, vigor and the need
for open space between the trees. Cross hedging facilitates movement
of men between trees, maintains fruit-bearing surfaces on all sides of
the trees, increases light access and air movement for better fruit col-
or and disease control and provides spaces for fruit containers. If
space is sufficient, it is possible to have more fruit-bearing foliage per
acre by maintaining fruiting surfaces around the tree. On the other
hand, cross hedging increases hedging and weed control costs and is
usually unsatisfactory in a close spacing of vigorous trees. Cross
hedging in bedded citrus may present some problems but it can be
done with appropriate equipment if it is dry between beds.
About 15 ft. (4.6 m) between trees seems to be the dividing line for
cross hedging, although some is done with closer spacings and not
done with wider spacings. Narrower middles of 4-6 ft. (1.2-1.8 m) can
be used for cross hedging because of less traffic in that direction, but,
to maintain satisfactory fruiting on those sides, the hedging angle








Fig. 3. Hedging angles of 50 (A), 150 (B) and 250 (C) from vertical.
The greater the angle, the greater the length of the sides,
the narrower the top and the longer the sides are exposed
to the sun.


A Hedging Angle of 50


B Hedging Angle of 150



























C Hedging Angle of 250


used should be sufficient to allow adequate light to reach them. This
is commonly done at an angle 50 to 100 from vertical. Where trees are
planted quite close in the row, cross hedging between every 2 or more
trees may be more practical than cross hedging to maintain individ-
ual trees, especially if they are vigorous. This allows those between to
grow together as units of foliage. The intervals between cross hedg-
ing should be consistent with harvesting needs.
Perhaps a more practical alternative would be to remove every
third or more trees, depending on tree spacings and other consider-
ations. This would allow groups of 2 or more trees to grow together as
units of foliage while providing the desired spacing and reducing
pruning requirements. Trees to be removed could be progressively
cut back, to allow normal growth of the permanent trees and removed
when they will no longer return a profit. The trees may be removed by
pulling, cutting them off at ground level or using a large self-
propelled tree shredder.
Some groves are hedged in only one direction so that hedgerows are
maintained. This practice has both advantages and disadvantages.
Some savings in pruning and weed control costs should be experi-
enced. However, pickers usually complain because it is difficult to get
between the trees and there is no good place to put fruit containers. A
change in harvesting methods may be justified for hedgerow plant-








ings. If the rows are quite close together, a greater bearing volume is
realized with hedgerows. Also, it can be difficult to keep the space
open and the sides between trees fruitful when vigorous trees are
closely spaced within the row.
Topping. Topping should be done before the trees have become ex-
cessively tall and should be a permanent part of a maintenance pro-
gram. Excessively tall trees are more difficult and expensive to har-
vest, coverage in the tops by sprays for pest and disease control is poor
and the fruit in the tops is often smaller. Topping trees at a suitable
height should reduce harvesting costs, improve pest and disease con-
trol, and increase fruit quality and size. Yield reduction due to top-
ping is usually not great if trees still have their skirts, especially
since fruit density is generally greater in shorter trees. However, if
the trees have lost their skirts, a large reduction in yield will occur in
the first year since most of the fruit-producing foliage would be re-
moved. Topping these trees would still be beneficial in the long run
since it would help them regain their skirts and bring them to a suit-
able height. Many groves are topped mainly to facilitate harvesting
because it is often difficult to get tall trees picked and a premium is of-
ten paid for all fruit picked from them. Topping would be advisable if
the total premium exceeds the value of fruit lost from a yield reduc-
tion. This largely depends on fruit price. Also, since topping usually
increases fruit size, fresh-market fruit from topped trees may be
worth more even if there is less of it.
Some trees are flat-topped, especially if they are small or narrow or
have been hedged at a wide angle. Closely-spaced rows, and those
with a sufficient hedging angle, can be flat-topped with a single pass
of the boom. However, most are topped at angles which may vary
from 15 to 30 degrees from horizontal, resulting in a peak which is 2
or more ft. (0.6 or more m) higher than the shoulders (drip) (Fig. 4).
Angles between these extremes are commonly used. The slope aids
the machine in sweeping the brush from the tops.
Optimum tree height depends on the distance between trees, the
hedging angle and tree width. Topping height may vary from about
10-20 ft. (3.1-6.1 m), but is usually about halfway between. Some
common topping heights are 12-14 ft. (3.7-4.3 m) at the shoulder and
15-16 ft. (4.6-4.9 m) at the peak. Lower heights are sometimes used for
training trees, increasing fruit size or rejuvenating declining trees.
Taller trees are sometimes maintained when they are vigorous and
widely spaced. Trees in the flatwood areas are generally topped about
2 ft. (0.6 m) lower than those in the ridge because the more limited
root systems will not support as much top growth. Some common top-
ping heights in these groves are 10-12 ft. (3.1-3.7 m) at the shoulders
and 12-14 ft. (3.7-4.3 m) at the peak. Topping should be started before



























Fig. 4. Trees topped at an angle of 200 from horizontal. The slope aids
the machine in sweeping the brush from the tops.

heavy cutting is required but, if this is necessary in an older grove,
the initial cuts should be low enough to avoid cutting heavy wood in
subsequent topping operations. Retopping is generally done just
above the old cut.
Pruning programs. A pruning program should begin before any
heavy cutting is necessary and should be continued at appropriate in-
tervals so that desired tree size and shape can be maintained at low
cost and with minimum loss of tree canopy. Regular maintenance
hedging and topping removes only a small portion of the tree canopy
if it is practiced soon enough and at proper intervals. A regular prun-
ing program eliminates the necessity for large cuts, maintains good
fruit production and simplifies brush disposal.
Hedging should be started before crowding becomes a problem in
order to maintain good fruit yields at a minimal cost. Maintenance
hedging between rows should begin when the trees are about 4 ft.
(1.2 m) from meeting so that not more than a foot or two of foliage is
removed from each side. When pruning is deferred until severe
crowding occurs, removal of a large portion of the tree results in ex-
cessive vegetative growth and a drastic reduction in subsequent
yield. In severe cases of crowding, the lower part of the tree canopy
may be lost due to excessive shading.
Hedging programs can vary considerably with variety, vigor, spac-
ing and grower preferences and practices. The schedule should be fit-








ted to the grove. The important objectives are to avoid overcrowded
conditions and heavy cutting of vigorous trees while maintaining
good fruit yields, size and quality. Regular maintenance hedging
eliminates the necessity for large cuts and simplifies brush disposal.
Vigorous, closely-spaced groves require more frequent maintenance
hedging. Some groves are on a yearly program of hedging all sides ev-
ery year while most are on programs in which a particular side is
hedged at intervals of 2-4 years. Annual pruning may be required to
hold vigorous trees within their allotted spaces and maintain drive
middles for orchard equipment. Some groves of specialty fruit have
been hedged on 4 sides one or more times a year to size fruit. Groves
on a 2 year program are hedged in one direction one year and the
other direction the next, or alternate middles are hedged in both direc-
tions every year. A 3 year program, which consists of hedging one
way the first year, the other way the second and topping in the third
year, is popular. A 4 year program can consist of hedging alternate
middles in one direction the first 2 years and alternate middles the
other direction the next 2 years, every middle in one direction the
first year and every middle in the other direction 2 years later, or any
other system which would result in each side being hedged once every
4 years. A 4 year program may be quite adequate for less vigorous
trees or those planted at a very wide spacing. The possibilities are nu-
merous and should be decided on an individual basis. A strict sched-
ule is not always practical, for various reasons. In many cases, cross
hedging is done less frequently because of less traffic in that direction
and less need to keep those middles as open.
Groves in which the trees are maintained as hedgerows may also be
on 1, 2, 3 or 4 year pruning programs. Here, the grower can hedge ev-
ery middle every year, hedge alternate middles every year, hedge ev-
ery middle every other year, hedge alternate middles for 2 years and
top the third year, hedge alternate middles every other year or hedge
all middles every 4th year.
The best time of year to hedge depends on variety, climate, severity
of pruning and when the job can be done. Since hedging is usually
done after removal of the crop, early maturing varieties are generally
hedged before those which mature later in the season. Many prefer to
hedge early, before bloom, but they also get more regrowth which
may or may not be desirable. Hedging could begin as early as Decem-
ber in warmer areas but in colder locations it is best to wait until the
danger of freezing temperatures is past. January, February and
March is the preferred pruning time for many growers. Heavy prun-
ing in April or May is risky if the grove is dry since it could suffer sun-
burn and dieback. Moderate hedging can be done to July with little or
no crop loss. A reduction in fruit numbers will often be made up by an








increase in fruit size. Light maintenance pruning can be done
throughout the summer and until early fall with little or no loss in
fruit production. Hedging should not extend very far into the fall
since tender regrowth is more susceptible to cold injury.
Hedging 'Valencia' orange or late harvested grapefruit presents a
special problem because of overlapping crops. There seems to be no
good time because fruit is on the tree at all times, either from the old
crop, the new crop or both. Hedging has usually been done in late
spring after the old crop is harvested and the new crop is set. Fruit
harvest should be scheduled early in the season for 'Valencia' groves
that are to be hedged. 'Valencia' groves which are not very vigorous
can be hedged every third or fourth year, after harvest. However,
good results have been obtained when annual hedging has been done
in late winter with the old crop still on the tree and before bloom. The
first cut is usually done after harvest and then the grove is rehedged
annually in January or February. When this is done annually at the
same width, the foliage removed contains few fruit and there is no re-
duction in yield.
Topping should also be started before heavy cutting is required.
Maintenance topping should be scheduled to avoid heavy cutting.
This is usually about every third year where vigorous regrowth has
occurred. Shorter time periods are usually not as economical but
trees with fruit destined for the fresh market may be topped annually
or even more often to maintain good fruit size and color and to facili-
tate harvesting. Long intervals may actually increase costs of top-
ping and brush disposal because cutting larger wood is slower and
there is more brush to dispose of. Also, vigorous trees could again be-
come excessively tall. Longer intervals may be suitable with less vig-
orous trees. Trees grown in shallow soils, such as bedded citrus, of-
ten require special consideration because the limited root system
cannot support as much top growth and fruit production. Topping
should be started when the tops of the trees start to become thin and a
break can be seen in foliage density. These trees are not only topped
lower, in general, but more frequently, to maintain them in a healthy
condition.
Severe topping should not be started until after the threat of freez-
ing temperatures is past to avoid possible cold injury. Generally, top-
ping begins in January and continues through March. It should be
completed before the spring flush of growth so that exposed limbs
would be covered with new growth before hot, dry weather later in
the spring. Adequate soil moisture at the time of topping aids recov-
ery and prevents dieback, especially in hot weather. Topping in April
or May without irrigation is risky. Timing is not as critical with light
topping if little fruit is removed, but it is best not to top in the fall to








avoid cold injury to new growth. Regrowth is more vigorous when top-
ping is done before a major growth flush. Topping before the spring
flush results in new growth that is more leggy than when it is done at
other times. Maintenance topping can be done in the summer after
the summer rains begin. Regrowth will be less vigorous at that time.
Light retopping in early fall when regrowth is even less vigorous
should be considered if regrowth is too leggy after severe topping in
the spring.
Pruning to increase fruit size. Fruit size is very important in
fresh fruit sales. Small sizes often result in a reduced pack-out and
lower prices which could mean an actual loss to the grower. In some
cases, the larger fruit are spot-picked and the rest of the crop is never
harvested unless it sizes up sufficiently. In more severe cases, an en-
tire crop may be left on the tree because it is not economically feasi-
ble to harvest it. Some cultivars grown for fresh fruit tend to set very
heavy crops of small fruit in some years and very light crops the next
year. Pruning after a heavy crop can increase alternate bearing and
result in a small yield of poor quality fruit in the next crop. Hedging
and/or topping after a light crop and before an expected heavy crop
can be used to reduce the numbers of fruit and obtain an appreciable
increase in fruit size. This should also reduce alternate bearing. The
grower may elect to speculate and prune before an expected large
crop is set or wait until after fruit-set so that the amount of fruit-set
can be more accurately determined. The latter should be done before
the fruit has attained appreciable size since later fruit removal could
result in a crop reduction without a compensating fruit size increase.
Sometimes specialty fruit trees are hedged and/or topped both before
and after bloom and fruit set. Fruit in the tops of tall trees is usually
smaller, particularly grapefruit. 'Ipping these trees will have a
greater effect on fruit size than will hedging.
Pruning lemon trees. Lemon trees are more open and irregular in
growth habit than other varieties of citrus and they require special
consideration. They are usually quite vigorous and produce numer-
ous long, upright shoots which bend over when terminal fruit are set.
Numerous laterals are produced on the bent branches so that un-
pruned trees grow into a tangle of weak, interlaced branches, which
makes harvesting more difficult and pest management less efficient.
These trees are productive but the fruit is generally smaller and often
scarred. Early tree training is similar to that for other citrus but re-
quires more attention due to the greater number of sprouts produced.
The terminals of long shoots are often cut back, preferably to laterals,
to prevent excessive bending. Frequent, light hedging and topping
are preferable to heavy pruning, to avoid excessive growth stimula-
tion. Unwanted and unfruitful shoots are selectively removed and








light thinning of the foliage promotes production of higher quality in-
side fruit. Hand pruning is usually done every second or third year.
Skirt pruning. Raising the tree skirts by pruning has both advan-
tages and disadvantages. Fruit on or near the ground is often of poor
quality because of cuts and bruises made by cultivation equipment.
Also, it is more subject to brown rot attack, and pest control is usually
less adequate in that area. Low skirts may also increase the incidence
of foot rot because of poor aeration and may interfere with the move-
ment of herbicide booms or other implements which pass under the
tree. Also, the lower limbs could be damaged by this equipment. Skirt
pruning is done by removing whole limbs at the trunk when appropri-
ate or by pruning only those subordinate branches which hang too
near the ground. Most growers do little or no skirt pruning because it
is an added expense and there may be a slight initial reduction in
yield. Also, more weeds can grow under the skirts and some growers
believe that high winds can cause more tree damage if the skirts are
off the ground.
Limb removal. When possible, large pruning cuts should be made
to sound, live wood and made flush with the trunk or parent limb or to
a lateral so that a stub does not remain. Healing of the cut area on a
stub of a large limb is retarded because it is out of line with the move-
ment of food and growth substances from the leaf area above it. New
shoots arising from latent buds at the end of the stub may eventually
aid healing. To avoid tearing of bark and splitting of wood, large
limbs should be removed in a 3-step process. The first cut is made on
the underside of the limb, several inches from its base and to about
1/3 of its thickness. The second cut is made downward,just beyond the
first until the limb falls. Then, with most of the limb weight removed,
the final, flush cut can be easily and safely made.
Pruning after freeze damage. Corrective pruning should be de-
layed until the full extent of damage can be determined. Sufficient
time should be allowed for new growth to take place and for dieback to
cease. Premature pruning can result in removing some limbs which
would recover, and in not removing some limbs or parts of limbs which
will die back further, both of which may slow tree recovery. Injury to
foliage and tender shoots usually becomes visible within a few days
but twigs and small limbs may show little or no signs of cold damage
for 2-4 weeks. It may be several months before severe injury to larger
limbs can be fully determined. Therefore, pruning should not be done
for at least 6 months after severe cold damage has occurred. All prun-
ing cuts should be made into living wood, below all serious bark dam-
age and at crotches or to a point where vigorous new shoots are grow-
ing. Further light pruning may subsequently be done when needed to
aid in forming a new framework.







Rejuvenation. Loss of tree vigor in older groves results in thin-
ning of the foliage, low yields of small fruit and is usually accompa-
nied by dieback of twigs and small branches. This decline may be due
to old age, disease, soil organisms, poor drainage, neglect, root dam-
age or other causes. The cause of decline should be determined and
corrected, if possible. Otherwise, the response to rejuvenation prun-
ing will be temporary.
A limited root system due to a high water table, a hardpan or a poor
subsoil can result in early tree decline and in trees more readily
stressed by drought or root injury. Topping these trees should restore
them to a more favorable top to root relationship.
Root damage may result from flooding, poor drainage, mechanical
injury, root weevils, nematodes, oil spills or various other causes.
When this occurs, the top becomes out of balance with the more limit-
ed root system and suffers from insufficient uptake of water and nu-
trients by the roots. The trees may recover without pruning if the
damage is not severe and the cause is corrected. However, in cases of
severe root damage, pruning to re-establish a proper root/top balance
will aid tree recovery. Hand pruning can be used for this purpose but
it is more practical to use topping and hedging machines if many
trees are involved.
Tree decline may also result from various disease problems. The
feasibility of rejuvenation pruning will depend on the disease in-
volved and its severity. Heavy pruning can sometimes extend produc-
tion for many years but in other cases tree recovery is too temporary
to be practical. When size and yield of the trees are reduced to an une-
conomical level, they should be replaced.
The severity of pruning to use for rejuvenation will depend on the
cause and degree of decline. Moderate hedging and topping may be
sufficient if the situation is not serious but severe pruning would be
required to rejuvenate trees in severe decline. Severe hedging and
topping will result in increased vigor, reduced tree size and relatively
rapid tree recovery..The operation can be completely mechanized and
a structurally sound tree remains (Fig. 5). Skeletonization, the re-
moval of all foliage and wood smaller than 1-1/2 in. (2.5-3.8 cm) in di-
ameter, invigorates the tree and results in production of fruiting
wood throughout the remainder of the tree. However, it is costly and
the crop is lost for a year. Buckhorning, cutting back the scaffold
limbs to a height of 5-6 ft. (1.5-1.8 m) above the ground, is the most se-
vere form of rejuvenation pruning. It results in vigorous growth,
greatly reduces tree size, and has a long-lasting effect. However,
large wounds remain, the tree is structurally less sound and produc-
tion is lost for about 3 years.


























Fig. 5. Rejuvenation pruning in an old 'Valencia' orange grove. All
trees were hedged. Those in the foreground were topped at 15
feet to invigorate the trees and to reduce them to a more man-
ageable height.


Protecting the tree after pruning. Large wounds are an open in-
vitation to bacteria and wood-rotting fungi. Wound dressings encour-
age healing of large pruning wounds and protect them against inva-
sion by disease organisms which can eventually cause dieback. It is
advisable to paint large wounds on or near the trunk but it may be too
costly to cover large wounds higher in the tree which result from
hedging and topping. Many types of wound dressings are available. A
water-based asphalt emulsion with a fungicide added has been quite
satisfactory. A white acrylic latex paint that is non-phytotoxic ap-
pears to be a good alternative.
Topping which exposes large limbs that have grown in the shade
may result in sunburn when done during or shortly before hot, dry
weather. Application of a whitewash to exposed surfaces of limbs and
trunks will prevent damage. Several formulas of whitewash have
been devised. A whitewash made of 50 lbs. (22.7 kg) hydrated lime
and 4 lbs. (1.8 kg) of zinc sulfate per 100 gal. (378.51) of water affords
good protection. Diluted white latex paint has been quite satisfac-
tory, but is more expensive. Application with a brush is suitable for a
few trees but the use of a power sprayer would be more efficient for a
large number of trees.








Closely-spaced groves. Many citrus growers have turned to
closer tree spacings as a way of achieving higher early and sustained
fruit yields to contend with increasing costs of land, production and
harvesting. Favorable results have usually been obtained in early
years but problems of over-crowding, excessive regrowth following
pruning and reduced yields have often developed later because the
trees were too vigorous for close spacings (Fig. 6).


Fig. 6. Trees in rows spaced 15' apart. Annual hedging is required to
keep the middles open for equipment and adequate light.

Pruning vigorous trees in a closely-spaced planting can lead to a
perpetual problem of excessive vegetative growth at the expense of
fruit production, unless properly carried out (Fig. 7). Severe cutting
should be avoided as much as possible. The more vigorous the trees
and the closer the spacing, the sooner pruning should be started and
the more often it should be done, so that only light cutting is neces-
sary and crop reduction is minimized. Slow-growing trees respond
more favorably to pruning and are easier to maintain at a given size
and shape without sacrificing yield. Tree vigor can be controlled to
some extent by proper selection of rootstock and scion and careful ni-
trogen control.
Growers with closely-spaced rows of relatively vigorous trees often
have a problem with hedging to large stubs. Pickers dislike them and
they are often struck by equipment. This may be corrected by hedging
an extra foot off each side and then coming back at the regular width


























Fig. 7. Excessive vegetative regrowth by young, closely-spaced trees
following hedging. Satisfactory fruiting on the sides of these
trees is often attained before they again become crowded.

the next time. Perhaps this would be better done in a 3-step process
which would begin by hedging a foot or two off-center to cut back the
larger branches on one side, while allowing the other side to grow and
fruit well. When hedging is again required, it should be done off-
center on the other side of the middle. Subsequent hedging should
then be resumed down the middle until a similar problem develops.
Frequently, long, vigorous shoot growth extends into the middles
and presents a problem. Most of this can be adequately controlled by
hedging. However, large, vigorous shoots which are cut back usually
produce vigorous new shoots and the problems redevelop. Excessive-
ly vigorous shoots should be selectively removed at their base to pre-
vent further problems with them.
This can be done fairly inexpensively every second or third year by
removing only those with which this difficulty is expected.

PRUNING EQUIPMENT
Appropriate pruning equipment should be selected for satisfactory,
economical results. A wide variety is available for purchase or use
through commercial operators. Small equipment may be more eco-
nomical for light pruning or in tight areas but, for heavier cutting,
larger equipment can often do a better job for less money, even
though the cost per hour is greater. No matter what equipment is








used, the blades should always be kept sharp since sharp blades do a
better job and require less power.
Hand-held equipment may be used for selective pruning or
where relatively few trees are involved. The simplest and least ex-
pensive pruning tools are powered by hand. These include hand
shears, long-handled loppers and pruning saws. The saw blades are
generally curved, cut when pulled and fold for easy carrying.
Hand pruning has been made easier with loppers or saws powered
by air, electricity or hydraulics. It is important that the power source
is adequate to meet the demands placed upon it. Otherwise, the oper-
ation may be slower and repairs more frequent. The cutting blades
are usually at the ends of poles of various lengths which extend the
reach of the operator.
Platforms for reaching higher in the tree include ladders for man-
ually-powered tools and mobile platforms for small power tools. Spe-
cial one-man machines are marketed by several companies and some
growers have mounted platforms on trucks and tractors.
Hedging machines vary considerably in size and design, ranging
from a tractor-mounted vertical boom with a row of belt-driven circu-
lar saws to rather large machines with 2 booms mounted on a self-
propelled or tractor-pulled chassis. Some have straight booms with a
row of saws on each while others have booms with rotating cross arms
with a saw at the end of each. The larger machines can do heavy cut-
ting more easily and rapidly. The booms on many machines can be ad-
justed to the desired width and angle.
Topping machines also vary from tractor-mounted booms.to larg-
er machines that are self-propelled or tractor-drawn. They also have
straight or rotating booms which can be adjusted to the desired top-
ping angle.
Preparation for hedging or topping should include having the
ground as level as practical so that the machine will not be slowed by
ruts or other impediments. Adequate turn areas should also be pro-
vided. Before topping, risers of overhead sprinklers must be taken
down and hedgiAg is sometimes needed to facilitate movement of
the machine through the grove and to allow the brush to fall into
the middles.

BRUSH DISPOSAL
The brush that results from pruning is often the biggest problem
and the greatest expense. Brush disposal can be handled in several
ways, depending on the amount and size. No special operation is nec-
essary when the size and amount of brush is rather small, since it will
decay where it falls or be broken up in routine mowing, discing or








chopping. However, in some cases this operation can be more expen-
sive than pruning itself.
Rotary mowers have been widely used for many years because of
relatively low costs. They are quite adequate when neither the
amount nor size of the brush is great. The mowers being used are de-
signed for heavy cutting and are often further reinforced for added
strength to absorb pounding by wood chunks. Safety precautions
must be taken to avoid injury by flying wood. This type of equipment
has been used on citrus brush up to 3 or 4 in. (7.6-10.2 cm) in diameter.
Larger wood should be cut off and removed from its path. The mower
should go over the brush on the day it is cut or the operation should be
delayed until the brush is brittle. In between these times, the brush is
much tougher.
Another method is to haul the brush out and burn it in a suitable
place. Equipment of various sizes and types can be utilized, depend-
ing on the job. Local burning laws should be complied with. In some
cases the brush can be dumped into a pit or sink hole.
Large, self-propelled brush shredders are relatively new in Flori-
da. These large, powerful machines can shred wood up to several
inches in diameter by means of heavy steel hammers or teeth. This
reduces the brush to small pieces which should not present any fur-
ther problem. These machines are practical in a heavy brush situa-
tion since they can do the job better and faster.

CONCLUSIONS
Pruning can have a pronounced influence on tree size and vigor,
production and harvesting practices, and fruit yield, size and quality.
Hedging and topping programs are successful only if they are well
suited to the groves for which they are intended. The best procedure is
to inspect the grove, decide on the desired results, consider the prun-
ing principles involved, select the appropriate methods and equip-
ment and then proceed according to what seems best for the particu-
lar grove situation.


rf






















































This publication was printed at a cost of $998.90, or 19.9 cents
per copy, to inform growers about pruning practices. 7-5M-80



COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLOR-
IDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES,
K. R. Tefertiller, director, In cooperation with the United Statesl
Department of Agriculture, publishes this Information to further the
purpose of the May 8 and .une 30, 1914 Acts of Congress; and Is
authorized to provide research, educational Information and other
services only to individuals and Institutions that function without regard to race, color,
sex or national origin. Single copies of Extension publications (excluding 4-H and Youth
publications) are available free to Florida residents from County Extension Offices.
Information on bulk rates or copies for out-of-state purchasers Is available from C. M.
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Galnesvllle, Florida 32611. Before publicizing this publication, editors should contact
this address to determine availability.




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