Commercial Leatherleaf Fern
Production in Florida
R. W. Henl yjkAiT Mrq .4---aolQtz
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences,
University of Florida, Gainesville, FL 32611 John T. Woeste, Dean for Extension
Authors express appreciation to the following University of
Florida Institute of Food and Agricultural Sciences faculty who
contributed technical information and advice during development of
C. A. Conover, Agricultural Research Center, Apopka
R. A. Dunn, Entomology and Nematology Department,
R. A. Hamlen, Agricultural Research Center, Apopka
D. S. Harrison, Agricultural Engineering Department,
F. J. Marousky, Agricultural Research and Education Center,
J. F. Knauss, Agricultural Research Center, Apopka
T. A. Kucharek, Plant Pathology Department, Gainesville
A. J. Overman, Agricultural Research and Education Center,
R. T. Poole, Agricultural Research Center, Apopka
J. B. Sartain, Soil Science Department, Gainesville
D. E. Short, Entomology and Nematology Department,
G. W. Simone, Plant Pathology Department, Gainesville
Appreciation is also expressed to L. A. Risse from the SEA-
USDA, Orlando, Florida and W. R. Miller from SEA-USDA, Rot-
terdam, Netherlands for contributions to the marketing and ship-
ping section of this bulletin.
TABLE OF CONTENTS page no.
Foreword ........................................... 2
List of tables ................................. 3
List of figures ........................... .............. 4
Introduction ............................ ............. 5
The leatherleaf fern .................................... 6
Location of fernery ................................... 8
Site preparation, planting and bed renovation ............. 9
Light intensity control ............................... 12
Fertilization and nutrition ............................. 16
Irrigation ........................................ 20
Temperature regulation ............................... 21
Diseases and other pests ............................... 25
Harvesting and preshipment handling .................... 34
Marketing and shipping ............................. .36
Problem solving ...................................... 40
Glossary of terms .............................. ...44
Bibliography ......................... ............. 45
LIST OF TABLES
1. Seasonal variation in light intensity in Florida as influ-
enced by shade level ........................... 13
2. Suggested fertilizer rates for production of leatherleaf
fern grown under 3000 to 5000 foot/candles (32280 to
53800 lux) .................................. 17
3. Salt indexes of selected fertilizer materials .......... 19
4. Desirable ranges of ten essential elements in mature
leatherleaf fern fronds........................... 19
LIST OF FIGURES page no.
1. Major parts of a mature leatherleaf fern plant........... .6
2. Diagram of the life cycle of a typical fern............... 7
3. Inside a modern fernery under polypropylene fabric
4. Rosemary branches placed on wood and wire frame
for fernery shade............................... 15
5. Leatherleaf fern beds under live oak canopy........... .15
6. A polypropylene covered fernery with a polyethylene
film liner on wall exteriors and a perforated liner
attached under the polypropylene fabric roof .......... .23
7. A polyethylene lined fernery equipped with forced air
heaters ....................................... 24
8. Lesions on leatherleaf fern stipes caused by Ascochyta
sp ........................................ ....26
9. Lesions on pinnules of leatherleaf fern caused by
Cercospora ..................................... 27
10. Development of Cylindrocladium pteridis on leather-
leaf fern pinnules................................ 28
11. Symptoms of Rhizoctonia injury to a leatherleaf fern
frond ........................................ 29
12. Injury to stipe and rachis from the leatherleaf fern
borer, Undulambiapolystichalis ............... .. ..31
13. Packing room with fronds on dipping racks which sit
upon portable bases that are pushed up to a vat of
water. They are then mechanically lifted from the
base, transferred into the vat and returned to the base
.... .................. ................ .......35
14. Box of 40 leatherleaf frond bundles in carton lined
with polyethylene film ........................... 36
15. Recommended stacking of header stack (first stack)
for fern box measuring 30 by 14 by 9 inches (76 by
36 by 23 centimeters) .............................39
16. Recommended parallel air channel stowage pattern for
fern boxes measuring 30 by 14 by 9 inches (76 by 36
by 23 centimeters) in van containers ................. 39
17. Commercial leatherleaf fern diagnostic form. ....... 41,42,43
Commercial Leatherleaf Fern Production in
R. W. Henley, B. Tjia and L. L. Loadholtz'
Florida leads the world in production of leatherleaf fern, with ap-
proximately 3000 acres (1200 hectares) in cultivation. Estimated
value of the 1975 crop was about 25 million dollars and the
estimated wholesale value in 1979 may be as high as 40 million
Leatherleaf fern, Rumohra adiantiformis (Polystichum adian-
tiforme), was first produced in Florida during the 1930's and 1940's
in small quantities, but major plantings were not started until the
early 1950's. Increased consumption of leatherleaf is attributed to a
preference by florists for use in floral arrangements. Superior keep-
ing quality, ease of shipping and more versatile design
qualities-form, texture and color-make the leatherleaf the most
widely used cut foliage in commercial floral arrangements and cor-
The highest concentration of leatherleaf ferneries in Florida is in
Volusia County, but considerable production also occurs in Lake,
Orange, and Putnam Counties. Small plantings of leatherleaf fern
can be found throughout Florida on sandy, well drained soils, in-
cluding northern sections where additional cold protection must be
Extensive plantings have been made in Central and South
America in recent years which will probably influence production
and marketing of leatherleaf in Europe and possibly the United
States. At this time, the degree of this impact is not known.
This publication provides growers information to maximize pro-
duction and quality of leatherleaf fern on a profitable basis. Struc-
tures, environmental control systems and cultural practices which
fail to meet this objective are not discussed.
'Associate Professor and Foliage Extension Specialist, University of Florida,
Agricultural Research Center, Apopka; Assistant Professor and Floriculture Ex-
tension Specialist, University of Florida, Gainesville, and Volusia County Exten-
sion Director, Deland.
THE LEATHERLEAF FERN
Leatherleaf fern is a true fern belonging to the family,
Polypodiaceae. Now correctly named Rumohra adiantiformis (G.
Forst.) Ching, leatherleaf fern was formerly classified as
Polystichum adiantiforme (G. Forst.) John Sm. It is native to
tropical areas of Central and South America, South Africa,
Madagascar, New Zealand and Australia. Growers have given
names to a few selections including Baker and Mayfield (1),
although most plant taxonomists do not recognize such names.
Leatherleaf fern is not sold by cultivar in the trade and unless some
very distinctive clones are selected and promoted, it is doubtful that
it will be. Only high quality leatherleaf with desirable frond shape
and keeping quality should be planted for commercial production.
Frond or complete leaf -
Pinna or primary
S. -. division of the
S '/ frond
Pinnule or secondary
division of the frond
SCrosier or expanding frond
Portion of stipe remaining /
after cutting Stipe Terminalbud
/ LStipe .-d-Terminal bud
Figure 1. Major parts of a leatherleaf fern.
Typically, leatherleaf fern leaves (fronds) are sturdy, dark, glossy
green and keep well after harvest (Figure 1). The petiole (stipe) of
leatherleaf fern grows erect and is covered with brown, hair like
scales. Frond blades have primary divisions called pinnae and
secondary divisions referred to as pinnules. In spring, rusty colored
patches known as sori develop on the underside of some fronds
(Figure 2). Sori are clusters of spore cases (sporangia). One spore-
bearing frond may produce hundreds of thousands of spores which
serve as the primary reproductive mechanism of the species in
nature. Leatherleaf rarely grows from spores in ferneries in Florida.
Young sporophyte with
frond and roots
developing white still
attached to the
Motile sperm, in film of
water, swim into the
archigonium which opens
at maturity and fertilizatic
Fully developed fern
and rhizoids on underside
antheridia containing sperm
Figure 2. Diagram of the life cycle of a typical fern.
Young fronds which develop near stem (rhizome) tips are tender and
vulnerable to drying injury and mechanical damage.
Leatherleaf fern is propagated commercially by rhizome (stem)
divisions or clumps to insure perpetuation of plants with desirable
characteristics. Leatherleaf fern propagated from spores may not be
true to type. The rhizome is usually free branching and develops
horizontally on or near the soil surface where it is anchored by
fibrous roots. The root system is easily injured when soil (1) is
mechanically disturbed (2) becomes very dry or (3) is infected with
root rot pathogens or nematodes. Young, actively growing roots
have white to yellowish tips while older roots are dark brown.
The fern life cycle is described in Figure 2. Fern development from
spores follows a cycle which includes sexual reproduction. When a
viable spore lands in a moist, shady environment, it germinates in
several days and produces slender cells rhizoidss) which secure the
young plantlet gametophytee) in place. The gametophyte then pro-
duces a green cell which develops into a thread of several green cells.
After about 3 months, the tip of the thread-like structure typically
grows into a flat, green, heart-shaped plate of tissue called a pro-
thallium. Located on the underside of the prothallium are male
structures (antheridia) bearing sperm and female structures (ar-
chegonia) each bearing an egg. Sperm are released from the an-
theridia and find their way to an egg in a film of water on the same
or a different prothallium. The union of a sperm with an egg is
known as fertilization and starts the sporophyte generation-the
typical fern which eventually bears spores.
The fertilized egg (zygote) divides to form an embryo or young
sporophyte which develops roots, stems and leaves. As roots grow
and become established in soil, the prothallium disintegrates, leav-
ing the sporophyte to develop. The prothallium, which continues to
live for some time if fertilization does not occur, eventually dies.
The first fronds produced by young sporophytes do not resemble
those of adult plants but successive fronds assume typical shape of
adult ones. A small, well established plant develops six months to a
year after spore germination. Leatherleaf fern is a relatively slow
growing species and may require another year for the sporophyte to
complete its development and produce spores. Once plants develop
spore bearing fronds, they are produced annually thereafter and the
life cycle begins again when spores are released from the sporangia.
LOCATION OF FERNERY
Leatherleaf fern can be grown throughout Florida, but warm loca-
tions in the central portion are preferred. Mature fronds are injured
by air temperatures below 28 degrees F (-2.2 degrees C), but
rhizomes survive 22 degrees F (-5.6 degrees C) air temperatures.
Most commercial plantings in Florida are located south of an east-
west line through Ocala and Palatka. Ferneries located in cooler
areas require more energy for cold protection.
Sandy, well drained soils well above the water table are best for
production of leatherleaf fern, although soils with clay or organic
matter present are also excellent, provided internal drainage is
good. Leatherleaf fern requires considerable moisture for best yield,
but plants cannot tolerate standing water or saturated soils for
more than 24 hours without sustaining damage. Good internal
drainage necessary for production of leatherleaf fern is usually
associated with soil types, 1, 2, 3, 4, 5, 8, 9, 12 and 17, as classified
by United States Soil Conservation Service in "General Soils Map
of Florida-1962" (8) and a companion publication (7).
Relatively level topography is preferred to (1) facilitate construc-
tion of shadehouses, (2) prepare beds and (3) resist excessive erosion
from surface runoff. Selection of land with few existing trees and lit-
tle brush minimizes clearing costs.
Leatherleaf fern requires shade for development of desired frond
shape and color. Many growers erect shadehouses for fern but some
growers still select hammocks with natural oak shade. Oak tree
shade provides a low cost source of shade initially, but long term
costs are increased as tree pruning is required to provide desired
shade level. Competition with trees for nutrients and water, insect
and weed problems and obstacles to mechanization (irrigation,
cultivation, etc.) are other problems associated with ferneries
located in oak hammocks. Shadehouses are recommended where
high yields are desired although natural oak shade can be used.
Other factors of importance in location of a fernery include land
cost, labor availability, access to good market channels, reliable
transportation and an adequate supply of good quality water.
PLANTING AND BED RENOVATION
The soil surface should be leveled as much as economically feasi-
ble when preparing the site. Irregular topography within a fernery
will create significant temperature gradients and surface runoff pat-
terns which create erosion problems. Some surface grading is usual-
ly desirable to insure uniform surface water infiltration during
heavy rains. It is difficult to standardize environmental conditions
on a site with rolling topography because of differences in
temperature, tendency for soil erosion and shifting of fertilizer and
pesticide residues with soil in surface water.
If permissible, cleared trees and other brush should be burned in
an area which will not be immediately planted with fern due to high
levels of potash and other elements which accumulate in the soil
from the ash. Arrangemnts should be made for disposal of debris if
burning is not permitted.
Soil low in organic matter may be enriched by spreading 2.0 to 2.5
inches (5.1 to 6.4 centimeters) of fibrous peat or similar organic
material on the surface of bed areas and incorporating it to a depth
of 6 inches (15.2 centimenters) prior to planting. Incorporation of
organic matter is most important for rapid establishment of new
plantings during the first year to year and a half (after which the
benefit of using an organic amendment is greatly diminished). If
drainage needs further improvement following incorporation of soil
amendments, beds should be formed approximately 4 to 6 inches
(10.2 to 15.2 centimenters) above aisles. Beds usually range 3 to 4
feet (0.9 to 1.2 meters) in width and should be oriented in a north-
south direction. Beds wider than 4 feet (1.2 meters) are difficult to
cut and maintain. Workers often step into wide beds and damage
fern when cutting or weeding if beds are wider than 4 feet. New
aisles between beds range between 18 to 24 inches (46 to 61 cen-
timeters) in width, but due to encroachment of the rhizomes and the
spread of fronds, aisles become narrower with time. Rototilling of
aisles will maintain desired aisle dimension and help control weeds.
Rhizome pieces can also be collected from the edge of aisles which
become too narrow due to fern encroachment.
In most cases, it is necessary to adjust soil pH and fertility prior
to planting leatherleaf divisions. Required calcium, magnesium,
phosphorus and microelements should be incorporated with the
organic amendments prior to planting. Leatherleaf fern grows well
when soil pH ranges between 5.5 and 6.0, although it will tolerate a
slightly broader range (5.0 to 6.0). If soil pH is within a desired
range but low in calcium or magnesium, calcium sulfate (gypsum),
or magnesium sulfate, or magnesium oxide, respectively, can be ad-
ded without appreciably altering pH. Using the double acid extrac-
tion procedure used by the University of Florida Soil Testing
Laboratory, available calcium oxide (CaO) and magnesium oxide
(MgO) readings should be adjusted to 1000 pounds and 250 pounds
per acre (1120 kilograms and 280 kilograms per hectare), respec-
tively. A range of 140 to 280 pounds of available P205 per acre (157
to 314 kilograms per hectare) is considered adequate.
Usually a minimum of 2000 pounds (2240 kilograms per hectare)
of dolomite and 1000 pounds (1120 kilograms per hectare) of super-
phosphate per acre is required on new fern beds on virgin Florida
soils. Sandy soils with pH of 4.5 require about 1000 pounds (1120
kilograms per hectare) of dolomite to elevate the pH to 5.5 while
sandy soils with pH 4.0 require about 1800 pounds (2016 kilograms
per hectare) of dolomite to elevate the pH to 5.5.
Most growers use rhizome pieces spaced closely, end to end in 3 or
4 rows the length of the bed. A few leatherleaf growers use 12 by 12
inch (30.5 by 30.5 centimeter) or 12 by 18 inch (30.5 by 45.7 cen-
timeter) spacing of clumps when planting beds. Wider spacing of
divisions in beds delays time to maximum frond production.
Research results indicate full production of leatherleaf can be ac-
complished after 1.5 years using 5 inch square (12.5 centimeter
square) clump divisions with 3 to 5 terminal buds and intact fronds
on 12 by 18 inch (30.5 by 45.7 centimeter) spacing. Plots planted
with small divisions-2 to 6 inch (5.1 to 15.2 centimeter) rhizome
pieces without fronds-took 2.5 to 3 years to produce maximum
yields (6). Establishment times for both plots would have been
longer if polyethylene lined structures and supplemental heat were
not provided for cold protection.
New fern beds should be planted with healthy divisions of the
best clones of leatherleaf available. Size of divisions used for plant-
ing will depend upon quantity of planting stock available and
distance and time required to transport it. Clumps with intact
fronds can be used when stock is abundant and the transfer to new
beds can be made quickly. Clumps 5 inches (12.7 centimeters) across
usually have 5 to 7 good fronds and at least 3 healthy terminal buds.
Larger clumps can be used. Terminal rhizome pieces as small as 2 to
6 inches (5.0 to 15.2 centimeters) with fronds intact can be selected
when propagation material is limited, but will take longer to
develop into productive beds. When rhizomes are prepared for ex-
port, fronds should be cut from rhizomes and soil and most roots re-
moved to conserve space and weight. Prepared rhizomes should be
carefully packed to prevent mechanical injury of terminal bud or
desiccation during transit.
Planting depth will markedly influence rate of bed establishment.
Divisions should be set no deeper than 0.5 inch (1.3 centimeters)
below the soil surface when clumps are used. Soil moisture should be
monitored closely to prevent excessive drying. Clumps with soil in-
tact will establish rapidly when positioned with the upper surface of
the rhizome clump positioned at the soil surface rather than below.
Rhizomes free of soil have few, if any, functional roots and should be
planted with 1 inch (2.5 centimeters) of soil covering the rhizome.
Planting deeper than 1 inch often results in delayed growth and loss
Fern beds planted on sandy soils often become less vigorous after
several years of production due to extensive rhizome growth at the
surface and from other unknown factors. Extremely old beds with
excessive rhizome growth should be replanted after soil is amended
with incorporated peat as suggested for new plantings.
LIGHT INTENSITY CONTROL
Leatherleaf fern producers utilize several methods of shading
their crops including fabric covered shade structures, lathhouses,
brush covered structures and tree canopy.
Fabric covered shadehouses
Fabric covered shadehouses are preferred to other shading pro-
cedures due to uniformity of shade level provided, longevity of
modern shade materials and the potential for a high degree of
mechanization within a well designed fabric covered structure
(Figure 3). Most of the early fabric covered shadehouses were
covered with saran but as polypropylene fabric became available
during the 1960's, it replaced saran because of its superior strength,
extended product life and reduced shrinkage.
Construction of polypropylene covered shadehouses with wooden
super structures usually employs 4 by 4 inch (10.2 by 10.2 cen-
timeter) posts 10 to 12 feet (3.1 to 3.7 meters) long spaced 10 to 12
feet or more on centers and tied together at the top with 2 by 4 inch
Figure 3. Inside a modern polypropylene fabric covered leatherleaf fernery.
(5.1 by 10.2 centimeter) or larger stringers. Size of the stringers
depends on post spacing. Stringers of 2 by 4 inch lumber are
satisfactory for posts on 12 foot (3.7 meter) spacing or less, but
heavier material must be used with wider spacing. High profile
shadehouses provide the advantages of cooler temperatures for
both plants and workers and increased flexibility for movement of
equipment and installation of irrigation systems but are more likely
to be damaged by high winds. Other methods of construction utilize
round wooden posts, pipe or reinforced concrete on 20 foot (6.1
meter) centers or more which are connected with heavy galvanized
wire of about 8 gauge or galvanized cable. Shade fabric is attached
to the wire or cable using a variety of techniques including nylon or
polypropylene cord or several types of metal fasteners.
Based on several years of research, leatherleaf fern is known to be
most productive when the light intensity ranges between 3000 and
5000 foot candles (32280 to 53800 lux). Ten to 15 years ago most
ferneries were designed to provide approximately 80 percent shade
or transmit 20 percent of the incident light. Under such conditions,
leatherleaf plants produce dark green fronds which are very flat.
Structures in Florida that provide 80 percent shade transmit 1800
to 3000 foot candles (19370 to 32280 lux) which is below the op-
timum light intensity range for highest yield. The influence of
season and shade density on transmitted light intensity in Florida
is presented in Table 1.
Table 1. Seasonal variation in light intensity in Florida as influ-
enced by shade level.'
Light intensity in foot-candles2
Actual shade Winter Spring Summer Fall
provided Dec.-Feb. Mar.-May June-Aug. Sept.-Nov.
0% (Full sun) 8,700 15,300 15,900 11,600
50% 4,350 7,650 7,950 5,800
60% 3,480 6,120 6,360 4,640
70% 2,610 4,590 4,770 3,480
80% 1,740 3,060 3,180 2,320
'Adapted from Weather Forecasting Service data, Gainesville, Florida.
"To convert to lux units multiply foot-candle value times 10.76.
Most modern ferneries are covered with polypropylene shade
cloth that provides 63 to 73 percent shade, with 73 percent shade be-
ing the preferred density. A number of different shade fabrics in a
variety of densities are now available. Black polypropylene fabrics
in a regular weave are the most popular but there are other products
available with lath weave having an alternating tight and open pat-
tern which permits more air penetration. These often result in lower
temperatures inside shadehouses during hot weather than in struc-
tures covered with fabrics of uniformly spaced strands.
Leatherleaf withstands light intensities in excess of 5000 foot
candles (53800 lux). However, fronds will be light green, thick and
curly and will lack commercial quality. Research results suggest
manipulation of shade levels between winter and summer periods to
increase frond production by approximately 15 percent in heated
structures if the winter shade level is reduced to 47 percent and later
shifted to 73 percent for summer production (5). The manipulation
can be accomplished by changing fabric or using a double layer
shading system which does not appear to be commercially feasible
at present. Manipulation of light intensity may become feasible
with more intensive cultivation of leatherleaf.
Some leatherleaf fern is still grown in lathhouses, sometimes
called "slatsheds", fabricated from cypress heartwood. Shortages
of cypress heartwood, and the increasing cost of materials and labor
have made construction of new lathhouses prohibitive for produc-
tion of leatherleaf fern. Because of excellent air movement between
lath, these structures are cooler than similar structures covered
with fabric shade materials. Lathhouses built for leatherleaf fern
production should provide about 65 to 70 percent shade.
Brush covered structures
Structures covered with rosemary (Ceratiola ericoides) can still be
found in a few areas (Figure 4). These structures are of historical in-
terest primarily. Dry rosemary is highly flammable and is especially
hazardous during winter months where open flame heaters are used.
Few brush covered structures are being constructed from rosemary
since it is scarce near fern producing areas and is expensive to
gather. Existing rosemary covered structures usually have posts 10
to 12 feet (3.1 to 3.7 meters) apart with 1 by 4 or 2 by 4 inch (2.5 by
10.2 or 5.1 by 10.2 centimeter) lumber stringers connecting them
together at the top. Usually galvanized chicken wire of about 2 inch
(5.1 centimeter) mesh is stretched across the stringers and rosemary
woven into the wire until the desired shade level is obtained.
Tree canopy shade
Approximately 40 percent of leatherleaf acreage has been planted
in oak hammocks (Figure 5). This shading technique is not recom-
mended for growers attempting to get highest yields possible.
*-. ... .." ,.,,_' t. ,3
Figure 4. Rosemary branches placed on a wood and wire frame for fernery
Figure 5. Leatherleaf fern beds under live oak canopy.
However, good quality fern can be produced under natural shade
and it costs less to establish a fernery in a hammock than build new
shadehouses. The primary productivity limitations of tree canopy
shade are non-uniform shade, damage to fronds from debris falling
from older trees, loss of equipment mobility in fernery, loss of bed
space to tree trunks difficulty in irrigation and competition for
nutrients by trees.
FERTILIZERS AND NUTRITION
Natural and synthetic organic materials, granular inorganic
blends, blends of these two, soluble formulations, liquid formula-
tions and controlled release fertilizers are available to fern growers.
Labor for preparation and application, cost of fertilizer and equip-
ment for application, risk of injury to plants, uniformity of applica-
tion and several other factors should be considered when selecting
fertilizer formulations which can be injected through overhead
sprinkler systems. Fertilization through sprinklers saves money on
labor but, may not always provide the most efficient use of
nutrients due to non-uniformity of water distribution and loss of fer-
tilizer in aisle areas which promote weed growth. Growers should
consider fertilizers which can be applied to beds only, since ground
water quality and environmental quality are of vital concern. Ap-
plication to beds only could save up to 40 percent of the fertilizer
bill. Materials which can be applied to beds include some of the
natural organic, granular organic-inorganic blends and the pro-
grammed release fertilizers.
Selection of a particular N:P,20:K20 ratio depends upon the soil
type and previous fertilization practices. Nitrogen is used in large
amounts by plants and is easily leached from soil during periods of
heavy rainfall or excessive irrigation. Researchers presently feel
that nitrogen sources should contain approximately 50 percent
nitrate and 50 percent ammoniacal forms. Unlike nitrogen,
phosphorus is used in smaller amounts and tends to accumulate in
many soils creating a nutritional imbalance in plants if applied ex-
cessively. Excessive soil phosphorus will fix several micronutrients,
especially iron, making them unavailable for plant growth. In most
situations a fertilizer with either a 2:1:2 or 4:1:4 (2) ratio of
N:P20s:K20 is satisfactory. The fertilizer ratio can be changed to a
1:0:1 or similar ratio if soil test or leaf analysis reports indicate high
levels of phosphorus.
The amount of fertilizer needed to produce the best yield of high
quality fronds is determined by light intensity, temperature,
amount of water from irrigation and natural rainfall and vigor of
root system as influenced by pathogens, nematodes and soil type.
Controlled experiments have demonstrated that the number of
fronds cut per unit area can be increased by increasing light inten-
sity from 1800 to 3000 foot candles (19370 to 32280 lux) to a range
of 3000 to 5000 foot candles (32280 to 53800 lux) and making a cor-
responding increase in fertilizer applied. Plants under 1800 to 3000
foot candles should receive approximately 25 percent less fertilizer
than plants growing under 3000 to 5000 foot candles to realize
similar production of good quality fronds. Since plant growth is
markedly reduced with cooler temperatures during winter months,
less fertilizer is needed by plants during these periods.
Suggested ranges for application of primary fertilizers are 400 to
600 pounds (448 to 672 kilograms per hectare) of nitrogen (N), 200 to
300 pounds (224 to 336 kilograms per hectare) of phosphoric acid
(P2,0) and 400 to 600 pounds of potash (K20) per acre per year (Table
2) (2). Magnesium (Mg) should be applied at the rate of 50 to 150
pounds per acre (56 to 168 kilograms per hectare) per year (2). If
nitrogen is applied at the 400 to 600 pound rate using a 8 to 12 per-
cent nitrogen fertilizer, the following analysis of microelements (per-
cent of actual element) is suggested: Manganese (Mn)- 0.03 to 0.06,
Copper (Cu) 0.008 to 0.015, Iron (Fe) 0.035 to 0.07, Zinc (Zn) 0.02
to 0.04 and Boron (B) 0.016 to 0.02 (2).
Liming material can be applied as required to adjust pH and sup-
ply calcium and magnesium. Dolomitic limestone is usually pre-
ferred because it provides additional magnesium. If soil pH is
Table 2. Suggested fertilizer rates for production of leatherleaf
fern grown under 3000 to 5000 foot candles (32280 to
element pounds/acre/month pounds/1000 ft2/mo
Nitrogen (N) 35-50 0.8-1.2
Phosphorus 15 25 0.3 0.6 Adjust accord-
(P205) ing to soil
Potassium (KO) 35 50 0.8 -1.2 If soluble salts
in soil or water
is high, avoid
'Reduce rates up to 50 percent through cold periods unless plants are growing under
'To convert to kilograms per hectare multiply pounds per acre value times 1.12.
within the upper limits (a condition which may be caused by irriga-
tion with water of high calcium content) an acid forming fertilizer
such as ammonium sulfate may be recommended. If calcium or
magnesium are deficient in the plant or soil they can be supplied by
calcium sulfate and magnesium sulfate, respectively.
Based on leaf analysis it may be desirable to apply micronutrients
such as iron, manganese, copper, zinc and boron. A micronutrient
supplement containing five to seven microelements can be applied
in granular or liquid form when micronutrients are generally low.
Some microelements accumulate in soils from certain fungicides ap-
plied to control foliar leaf spots. Single source microelement fer-
tilizers should be selected if only one or two microelements are defi-
cient. Indiscriminate additions of a wide spectrum micronutrient
supplement often results in accumulation of one or more elements
which reach toxic levels. Visually recognized microelement deficien-
cies in leatherleaf plants are rare.
High soluble salts or high salinity in beds markedly reduces pro-
ductivity of leatherleaf fern because roots cannot tolerate excessive
salts. Moderately high soluble salts in root zones will reduce plant
productivity without permanent injury. Excessive salts in root
zones will injure and eventually kill roots and plant. Soluble salt ac-
cumulation from excessive fertilization or insufficient irrigation to
provide for some leaching are problems which can be avoided.
Producers using water of fair or poor quality should irrigate with
sufficient water to prevent accumulation of fertilizers and other
salts in beds. Fertilizers with low salt indexes should be used when
salt accumulation is a problem due to improper irrigation practices
or poor water quality ( high analysis fertilizers such as 20:10:20,
generally have a lower salt index than low analysis types, such as
10:5:10, for equivalent amounts of actual nutrient).
Table 3 lists several fertilizer materials and their respective salt
Soil and plant tissue analyses
Leatherleaf fern is grown under numerous fertilizer programs
determined by soil type, application technique, grower under-
standing of plant needs and grower effort to maximize production.
A good fertilizer program should utilize both soil and leaf
analyses services. Since extraction procedures and methods of ex-
pressing soil test results vary considerably among laboratories, sug-
gested ranges for specific elements or ions are not mentioned in this
publication. Conversely, foliar analysis values have nearly universal
application if testing is done by a reliable laboratory. Suggested
foliar nutrient concentrations for leatherleaf fronds are displayed in
Table 4. Fronds not fully expanded and hardened or over 2 months
beyond cutting stage should not be used for leaf analysis. Both soil
and leaf tissue tests should be used several times a year to insure
good nutritional status of leatherleaf crops.
Table 3. Salt indexes of selected fertilizer materials.1
Salt index of
Fertilizer Percent fertilizer
compound nutrients) compound
Potassium chloride (60% KO2) 116
Potassium chloride (50% KO) 109
Ammonium nitrate (33% N) 105
Urea (45% N) 75
Potassium nitrate (13% N+45% KO) 74
Ammonium sulfate (20% N) 69
Calcium nitrate (15% N+19% Ca) 53
Potassium sulfate (48% K20) 42
Diammonium phosphate (21% N+54% P,O,) 34
Monoammonium phosphate (11% N+48% P206) 30
Concentrated phosphate (45% P20,+14% Ca) 10
Regular superphosphate (19% P20,+20% Ca) 8
Gypsum (29% Ca) 8
Calcium carbonate (32% Ca) 5
'The salt index is obtained from conductivity measurements and is an indication of
the relative influence of a particular compound on increasing the soluble salt level
in the soil solution when equal weights of each compound are used.
Table 4. Desirable ranges of ten essential
leatherleaf fern fronds.
elements in mature
2.0 to 2.8
0.22 to 0.40
2.3 to 3.4
0.3 to 0.7
0.2 to 0.4
25 to 75
10 to 30
100 to 400
40 to 150
30 to 150
'Composition of fronds is expressed on dry weight basis.
Leatherleaf fern can become subjected to moisture stress by
several factors-long periods without rain or irrigation, well drained
soils with limited moisture holding capacity, shallow root systems,
large foliage surfaces or shifts in relative humidity, air temperature
and wind velocity. Plant growth and fern productivity are markedly
reduced under moisture stress. Frequency of irrigation should be
determined by local weather conditions and a judgement by growers
regarding moisture content of beds prior to irrigation. Usually 0.5
to 1 inch (1.3 to 2.5 centimeters) of irrigation water applied to the
beds will wet soil sufficiently deep to satisfy plant needs without ex-
cessively leaching fertilizers. Small amounts of water applied fre-
quently provide an environment-wet foliage and high relative
humidity-that is ideal for development of numerous foliar fungal
diseases. If soil is kept excessively moist, root rots caused by fungi
such as Pythium may cause damage to fern roots and rhizomes. Ex-
cess water applied overhead will reduce effectiveness of pesticide
spray residues. About 1 inch (2.5 centimeters) of water every 3 days
through the summer, with compensation for natural rainfall and 0.5
inch (1.3 centimeters) every 4 to 7 days through winter months will
normally meet plant requirements.
Overhead irrigation is currently used by most leatherleaf pro-
ducers for crop irrigation. A well designed sprinkler system pro-
vides 100 percent overlap of water distribution patterns from the
heads. Most sprinkler heads used by leatherleaf growers are impact
or spinner designs. Other types are available, but usually do not
have the range of these and, therefore, have higher installation
Detailed information on construction of irrigation systems for
leatherleaf fern production is available in the publication entitled
"Irrigation Design for Leatherleaf and Plumosus Fern in Florida"
(3) which is available upon request from your local County Exten-
sion Agent or the Agricultural Engineering Department, Institute
of Food and Agricultural Sciences, University of Florida,
Gainesville, Florida 32611.
Water quality is important when considering location of a fernery
and selection of fertilizers. Deep well water is recommended for ir-
rigation of leatherleaf because soluble salts are usually low and
transfer of pathogens, nematodes, weed seed and particulate
material is eliminated. Water from shallow wells, canals, rivers and
ponds should be avoided.
Need for high quality water for irrigation of fern beds cannot be
overemphasized. Salt levels up to 600 ppm in the water are con-
sidered acceptable for leatherleaf production. Water with salt levels
between 600 and 1200 ppm can be used if beds are kept relatively
moist and are leached on a regular basis. Water containing over
1200 ppm total salts is not suitable for cultivation of leatherleaf fern
if good yields are expected. Soluble salts in deep well water is a
problem in some areas due to salt water intrusion of the freshwater
aquifer. Growers should contact their local County Extension
Agents for procedures to follow for water tests.
Leatherleaf fern producers must be concerned with extremes of
heat and cold which influence frond yield, quality and worker pro-
ductivity. Most growers are concerned about low temperatures
which suppress growth and injure fronds. Visually detectable injury
of immature fronds usually occurs after exposure to temperatures
below 30 degrees F (-1.1 degrees C). The precise temperature causing
injury will depend upon plant vigor, maturity, nutritional status of
the fern, frond moisture content, wind and length of exposure.
Systems of cold protection being used include gas and oil heaters,
sprinkler irrigation and plastic film lined structures.
Open flame oil heaters such as the jumbo cone and return stack
units provide some protection but are of limited value because of
poor utilization of heat generated and poor distribution. There is
risk of injury to personnel and damage to fern plantings and struc-
tures when fueling open flame heaters.
Agricultural engineers have demonstrated that some sprinkler
systems used for irrigation can also protect a number of crops, in-
cluding leatherleaf fern if properly employed. Low angle, double
headed sprinklers which supply at least 0.3 inches (0.8 centimeters)
of water per hour should be used. Even if the air temperature drops
below 32 degrees F (0 degrees C), the leaf temperature will remain
approximately 32 degrees F if the sprinklers are kept in operation.
The irrigation system must be started when the air temperature is
32 to 34 degrees F (0 to 1.1 degrees C) at crop level and operated con-
tinuously until ice from the freeze has melted or the wet bulb
temperature rises to 32 degrees F or above.
Sprinkler irrigation used for freeze protection is effective and
relatively economical although it creates a number of serious prob-
lems. Heavy pumping in some areas has contributed to decreases in
water quality due to saline water intrusion of good quality water.
Heavy pumping reduces the level of the aquifer during pumping and
for several hours afterward and may contribute to sinkhole develop-
If an irrigation system cannot be operated continuously
throughout the freezing period, or it is not operating properly,
damage will be greater than if the system was not used. Damage oc-
curs when foilage covered with ice reaches the "wet bulb"
temperature which may be 2 to 10 degrees F (1.1 to 5.6 degrees C)
below the "dry bulb" temperature from evaporative cooling.
Another drawback to sprinkler cold protection is excessive
leaching which lowers soil fertility and subsequent crop yield.
Possibly the most serious problem created from liberal use of water
for cold protection is the creation of. an ideal environment for
development of root rot organisms and loss of roots from poor soil
aeration. In some instances significant soil erosion can also occur
during a cold protection irrigation period where ferneries are
situated on sloping surfaces. Use of sprinklers as a means of protec-
ting leatherleaf from cold is not advised in fernery structures
covered with winter polyethylene.
Recently there has been some interest in a new technique of cold
protection known as high pressure fog. The fog system employs
automatic temperature sensing controls, a high pressure pump, a
high quality filter system and special nozzles which emit particles of
water averaging 10 microns in diameter when the system is
operating at 500 pounds per square inch (35.2 kilograms per square
centimeter). Each row of nozzles generates a layer of fog which pro-
vides a thermal barrier between the crop and the cooler air above.
Since high pressure fog is still in the experimental stage in Florida,
it is too early to strongly recommend the system for cold protection
of leatherleaf fern.
Covering ferneries with 2 or 4 mil (0.05 or 0.10 millimeter)
polyethylene is a good method of protecting leatherleaf from frost
(Figure 6). Other transparent or highly translucent films are on the
market, but polyethylene is the most economical product for this ap-
plication. Polyethylene to be used overhead is perforated in the roll
by drilling a series of 0.4 to 0.5 inch (1.0 to 1.3 centimeter) holes
spaced on approximately 12 inch (30.5 centimeter) centers with an
electric drill. The perforated cover will allow rain water to run
through and prevent water loading which can destroy a structure.
Polyethylene film is applied inside ferneries by attaching it to sides
of stringers between posts and pulling it tight. Galvanized 12 gauge
wires pulled perpendicular to the length of the polyethylene sheets
under the fabric shade material supports the plastic film liner when
it is in place under the shade cloth. Shadehouses constructed from a
Figure 6. A polypropylene covered fernery with a polyethylene film liner
on wall exteriors and a perforated liner attached under the poly-
propylene fabric roof.
series of widely spaced posts and overhead cables or heavy wires
which support fabric shade cannot be lined unless additional
wooden stringers are added for liner attachment. Polyethylene
liners should be installed by mid November and removed by mid
March. Ventilation of lined shadehouses on warm days is ac-
complished by rolling up film on sides or opening a section through
The most sophisticated techniques of protecting leatherleaf from
cold injury is through combined use of plastic film lined
shadehouses and forced air unit heaters which provide a uniform
and efficient means of protection (Figure 7). Winter temperatures
should not be allowed to drop below 35 degrees F (1.7 degrees C) on
the coldest nights if plastic lined shadehouses are used, otherwise
productivity of plants will be markedly reduced. Vented forced air
unit heaters are preferred to provide the required heating. However,
properly adjusted non-vented heaters can be used without danger of
air pollution when perforated films are used to line the roofs.
Heating units with fans are preferred to obtain the most uniform
distribution of heat possible. Units which burn good quality, low
sulfur fuel oil, liquid propane and natural gas are most commonly
Figure 7. A polyethylene lined fernery equipped with forced air unit heat-
ers: heaters are draped with polyethylene for weather protection
when not in use.
Shadehouses lined and heated for cold protection represent an ad-
ditional expense but benefits derived from these steps make the in-
vestment worthwhile. Winter production in lined and heated
shadehouses will be high and injury associated with cold or heavy ir-
rigation will be virtually eliminated. A steady supply of quality
fronds through winter is desirable because the demand for
leatherleaf is usually highest through winter months. A well man-
aged fernery with lined and heated structures should yield between
750,000 and 1,000,000 fronds per acre (0.41 hectare). One acre of
fernery has approximately 30,000 square feet of bed area.
Ventilation of shadehouses
Ventilation and control of excessively high temperatures at crop
level is of less concern to most leatherleaf fern producers than pro-
tection from low temperatures. There are three primary factors
which contribute to reduction of high temperatures within
shadehouses other than irrigation. These include height and con-
figuration of structure, type of fabric shade and system of side ven-
Higher profile structures are cooler at crop level. Structures with
9 to 10 foot (2.8 to 3.1 meter) high ceilings are preferred over 6 to 8
foot (1.8 to 2.4 meter) high houses. Tall structures provide both
superior summer environment for the fern and laborers and more
flexibility for automation and mobility within the structure.
Shadehouses can be designed with breaks in the otherwise solid
fabric canopy, but these are not generally employed by the fern
growers. Designs which employ overlapping strips elevated 1 to 2
feet (0.3 to 0.6 meters) over the primary aisles or roads in the fernery
which may be spaced 100 to 200 feet (30.5 to 61.0 meters) apart per-
mit much of the trapped hot air to escape.
Houses covered with coarse weave shade fabrics are cooler than
houses covered with tightly woven fabric that produce the same
degree of shade. Large holes associated with coarse weaves provide
increased rate of air exchange. Additional cooling can be obtained
from cross ventilation by rolling up plastic liners along side sections
DISEASES, INSECTS, NEMATODES, WEEDS,
OTHER PESTS AND PHYSIOLOGICAL DISORDERS
This section deals with descriptions of problems commonly en-
countered in leatherleaf production, some of the cultural procedures
which will help control them and a few general remarks concerning
use of pesticides. Specific information on pesticides for use on
leatherleaf fern in Florida is outlined in a leaflet prepared by the
Florida Cooperative Extension Service titled: "Disease, Insect and
Nematode Control Guide for Commercial Leatherleaf Fern Produc-
tion in Florida". This may be obtained from your local County Ex-
tension Agent or from Ornamental Horticulture Department,
University of Florida, Gainesville, Florida 32611.
Root rot diseases
Most root rots of leatherleaf are caused by fungi belonging to the
genera Pythium and Rhizoctonia. Diseases caused by Pythium are
most prevalent when soils are maintained moist to wet for pro-
longed periods. Use of well drained soils, formation of beds which
are slightly raised above the aisles, close regulation of crop irriga-
tion and use of systems other than irrigation for cold protection will
do much to control Pythium root rots.
Rhizoctonia is a pathogen associated with root and rhizome decay
when soil and air temperatures and humidity are high. Decays
caused by this pathogen are usually located near or at the soil line
where soil aeration is good.
Fungal leaf spot diseases
Several diseases of leatherleaf fronds are caused by pathogenic
fungi. Many of these foliar leafspots are prevalent during warm,
humid periods when fronds remain wet for prolonged periods from
rainfall, irrigation or dew. Leafspot diseases most commonly
associated with leatherleaf are caused by pathogens from the follow-
ing genera: Alternaria, Ascochyta, Cercospora, Cylindrocladium
This leafspot is less commonly detected than others, but may be
more prevalent than recognized because of the difficulty in visually
distinguishing it from those caused by Cylindrocladium and Cer-
cospora spp. Lesions are usually definite, reddish brown spots
which may occur irregularly on leaf tissue. Alternaria leafspot ap-
pears to be most common in late spring and early summer and again
in mid fall.
Figure 8. Lesions on leatherleaf fern stipes caused by Ascochyta sp.
Ascochyta leafspot and blight
The fungus, Ascochyta necans, attacks immature fronds during
prolonged wet and cool periods in the spring, causing severe distor-
tion and making them unsalable (Figure 8). Only immature tissue is
susceptible to invasion by the pathogen. Symptoms of infections
range from discrete leafspots to severe frond distortion and decay.
Leafspots which are primarily circular may be only a few
millimeters in diameter. Ascochyta may also cause elliptical lesions
on the stipes of leatherleaf fern (Figure 9).
Figure 9. Lesions on pinnules of leatherleaf fern caused by Cercospora.
The leafspots caused by Cercospora spp. are typically small and
bright reddish brown (Figure 10). This disease is especially
prevalent when relative humidity is high and dew remains on plants
for long periods.
Cercospora is usually common from early to mid spring and mid
to late fall.
This fungus causes the most severe foliar disease of leatherleaf
where proper fungicide spray programs are not followed. It is par-
ticularly prevalent during warm to hot and wet periods, but may be
found throughout the year. Lesions are variable in size but are
usually a deep reddish color. Disease development can occur so
rapidly under optimum conditions that some growers refer to the
disease as "fire". In addition to the frond blades, stipes are affected
along with the rhizomes. Cylindrocladium resides on infected tissue
and on leatherleaf debris above and below soil level.
Figure 10. Development of Cylindrocladium pteridis on leatherleaf fern pin-
Rhizoctonia frond blight
The foliar disease commonly called frond blight is caused by the
soil borne fungus, Rhizoctonia, which normally infects fronds only
during warm, wet conditions. The wet infected tissue is dark brown
(Figure 11) where active disease development occurs. Lesions
become tan colored as they dry. Infected fronds frequently become
matted together by conspicuous dark reddish brown threads
myceliumm) of the fungus.
Symptoms of several of the fungal leaf spots are similar, thus, it is
recommended that frond samples be sent to the Extension Plant
Diagnostic Laboratory in the Plant Pathology Department, Univer-
sity of Florida, Gainesville, Florida 32611, where tissue from the le-
sions can be cultured and specific pathogens identified. Occasion-
ally, a fungal disease develops so rapidly that producers must at-
tempt to suppress it before laboratory reports are received. Select a
broad spectrum foliar fungicide from the pest control guide and ap-
ply thoroughly at recommended rates.
Figure 11. Symptoms of Rhizoctonia injury to a leatherleaf fern frond.
Frequency of foliar fungicide sprays depends upon the initial
disease levels and prevailing environmental conditions-moisture,
temperature, etc.-which influence disease development. The
presence of free moisture is necessary for development of all known
foliar fungal diseases of leatherleaf fern, therefore, the length of
time plants are wet is extremely important. Density of fronds
should not be permitted to get too high prior to cutting as losses can
be sustained as a result of excessive humidity, slow drying of foliage
and poor penetration of spray materials. Losses in production can
be expected, even if disease is not present, when beds become
overgrown, because new fronds become distorted from crowded sur-
Distribution of foliar applied fungicides and other pesticides is ex-
tremely important. Correct combination of nozzle, sprayer pressure,
spreader sticker, tank agitation, applicator's technique and frequen-
cy of application collectively determine effectiveness of a spray pro-
gram. Since airblast sprayers have become popular with many
growers in recent years, proper calibration of these sprayers is very
important. Irrigation systems are used by some growers to apply
foliar fungicides in an effort to save labor, but they are not recom-
mended for this use because of their large droplet size and non-
uniform coverage. Upper and lower surface of foilage should be
covered with spray material. It is impossible to develop a "cook
book" schedule for disease control because human judgement is re-
quired to determine frequency of spraying during various seasons
depending upon specific environmental conditions and type of
organism which is being controlled. Spray applications are normally
made every 7 to 10 days, although applications may be needed as
frequently as every 3 to 4 days during extremely hot, wet periods.
Applications can be spaced 2 to 4 weeks apart under dry conditions,
however, when dew remains on the foilage, applications may be
needed every 10 to 14 days.
Ferneries should be kept as clean as possible. Dead and diseased
fronds and other plant parts should be removed since they are
sources of inoculum for healthy fronds. A combination of sanitation
and well timed, thoroughly applied, foliar fungicides will provide ac-
ceptable disease control.
Diseases caused by bacteria and viruses
Diseases caused by bacterial and viral pathogens are not con-
sidered a threat to productivity or quality of leatherleaf fronds.
Bacterial growth in holding vessels where bunched fronds may be
held for short periods prior to packaging can cause problems.
Vessels used for holding leatherleaf fronds should be cleaned fre-
quently and fresh water used with each batch of fronds processed.
The same sanitation precautions should be taken with water tanks
used to dip the fronds prior to packaging in the shipping cartons.
Insects can be a serious problem in production of leatherleaf fern
if pest populations are permitted to proliferate. Generally, insec-
ticides should not be used regularly on a year round basis, since
many pests are seasonal. Observe plantings on a regular basis and
be prepared to use insecticides or miticides as needed. Inclusion of
an insecticide in the spray tank each time ferns are sprayed for
disease control is wasteful and not recommended. Pesticides recom-
mended for use against insects and related pests of leatherleaf are
outlined in the pest control guide mentioned previously.
The most important insects and related pests of leatherleaf in-
clude: caterpillars, grasshoppers, leafhoppers, leatherleaf fern borer
(larva), spider mites, thrips, termites, snails, and slugs. Caterpillars,
grasshoppers, slugs and snails normally feed on the foliage although
some slugs and snails also feed on plant roots. Damage to fronds
from foliage feeding pests is usually conspicuous.
Occasionally, some fronds in a bed will wilt for no apparent
reason. One or more internal tunnel patterns can be observed upon
close examination of the stipe or rachis (Figure 12). Injury of this
type is caused by the leatherleaf borer, Undulambia polystichal.
Larva of this moth can be easily observed once injured portions of
the fronds are opened. Usually those portions of fronds above the
region where larvae have fed wilt and eventually turn brown and
Figure 12. Larva (left) and pupa (right) of the leatherleaf fern borer Undu-
lambia polystichalis, in fern stipes. Center photo is of a darkened
stipe section which contains the larva or pupa.
Leafhopper injury to leatherleaf fern is characterized by fronds
having many small, white or necrotic spots. Also, stunting and
malformation of fronds occurs. Leafhoppers are rarely seen on
plants at the time injury is observed.
Thrips injure leatherleaf fronds as a result of a rasping and suck-
ing feeding habit. Symptoms of thrips damage include injured
tissue having a whitish or silver flecked appearance.
Termites are not regarded as a serious pest and are found pri-
marily in oak covered ferneries where little or no insect control
materials are used. Termites are not known to invade healthy tissue
of the leatherleaf fern, but rather invade the dead, backsections of
Spider mites are usually not a serious problem in leatherleaf
plantings unless mite populations have expanded on crops or weed
hosts adjacent to ferneries. When preferred hosts die or weaken
from heavy mite feeding, some mites leave the original host and
move on to another species of plant. A stippled chlorotic pattern can
be seen on the upper side of the frond following heavy mite feeding.
Several species of nematodes have been associated with root
systems of leatherleaf fern, but the lesion nematode, Pratylenchus
penetrans, is the most serious. These microscopic roundworms in-
jure roots and rhizomes causing reduced plant vigor and subsequent
losses in production. Severely infected plants grow very slowly and
produce light colored, small fronds.
New plantings can be assured of a good start if beds in
shadehouses are fumigated prior to planting and relatively clean
plant material is used for stock. Pre-plant, bare root dips and post-
plant, soil nematicide applications are used by growers to maintain
It is impossible to maintain nematode-free bed plantings of
leatherleaf fern because reinfestation occurs from dirty tools, move-
ment of infested soil into planting areas and migration of nematodes
through the soil. Therefore, periodically treat beds with an ap-
propriately labeled nematicide. A listing of nematicides for use on
leatherleaf can be found in the Florida Cooperative Extension Ser-
vice leaflet mentioned previously. Beds should be treated with a
nematicide about twice a year for best results.
Rodents and other animals
Armadillos, skunks, moles and salamanders have been destruc-
tive to leatherleaf fern plantings in some areas, especially those in or
near large wooded areas. Damage usually occurs at night when
these pests dig or uproot plants while searching for soil borne in-
sects and worms.
The best way to eliminate disturbances by these pests is tO
eliminate their food supply. Other than using traps and bait,
elimination of these pests is rather difficult in areas where a natural
stand of trees is used for the fernery. Soil-borne insects are rarely a
problem in areas where ferneries are located independently of trees.
Soil treatment or fumigation in shadehouses eliminates these in-
Weeds are serious in a number of ferneries where they have been
permitted to become established and compete with fern for
nutrients and light. Rototilling or using contact herbicides on weeds
in aisles plus hand weeding beds is still considered a good method of
restraining weed populations. Weeds in aisles which produce seed or
creep into beds are a primary source of weeds which develop in beds.
For this reason, it is important to maintain clean aisles.
Some herbicides have been used by fern producers, but none are
presently labeled for use in leatherleaf fern beds. Several growers
have tried a variety of herbicides in the aisles. Products which are
non-selective and persistent can be washed or splashed into the beds
when applied to aisles and damage plants over a long period. Non-
residual contact or systemic herbicides have also been tried with
some success when applied as a carefully directed spray.
Selective and frequent cutting of fronds from beds maintains
more shade on the soil surface of the beds than if they are cut heavi-
ly on a less frequent basis. A combination of aisle cultivation,
maintenance of relatively dense canopy of fronds over the beds and
hand weeding of beds is suggested for control of weeds.
A number of producers described a problem called "fern wilt", a
postharvest physiological disorder which seems to be prevalent
during warm periods of the year when ferns grow rapidly. The prob-
lem is believed to be physiologically induced and results in frond
wilt approximately one week after harvest, which is approximately
25 percent of normal shelf life of the product when held under
refrigerated conditions. To date, pathogens and vascular blockage
have not been associated with "fern wilt".
"Red edge" is a physiological disorder which was once thought to
result from calcium deficiency. Efforts to produce "red edge" symp-
toms under experimental conditions have not been successful. "Red
edge" appears as a rusty to red margin around the pinnules and
seems to be most prevalent in early spring. The cause of "red edge"
is still not known.
Other patterns of frond discoloration
A variety of other off color patterns are observed in the fronds
produced commercially at various seasons and in different areas.
Most poor coloration not attributed to diseases or other pests is felt
to be caused by improper nutrition, injurious temperatures or ex-
cessive irrigation. Other factors may be involved but are not as
widespread as those mentioned.
HARVESTING AND PRESHIPMENT
Leatherleaf fern fronds are harvested with hand labor which is
relatively slow and expensive. Harvesting requires bending over
beds and reaching to the ground where stipes are cut. Extreme care
should be taken to avoid stepping into beds and injuring fronds and
rhizomes. All cuts should be made as close to the rhizome as possi-
ble to avoid leaving long, sharp sections of the stipe protruding
from the rhizome which can injure cutters' hands when beds are cut
Fern cutters should be advised to cut only those fronds which are
dark green, fully expanded and mature. Immature fronds not fully
expanded and hardened have poor keeping quality, bruise easily and
are not desired by the florist trade.
Researchers have studied the feasibility of mechanized harvesting
to minimize labor costs, but a satisfactory system has not been
developed. Mechanical harvesting of leatherleaf fern does not
distinguish between fronds which are ready for harvest and those
which are not, resulting in considerable waste of non-usable fronds.
Care of fronds after cutting has a strong influence on subsequent
keeping quality in retail outlets and in hands of consumers. Usually
25 fronds are placed in a bundle and tied with an elastic band or
string and placed in aisles between beds. Bundles are collected,
transported to the packing building and allowed to harden by im-
mersing them in water or submerging the stipes in water for a
period of time (Figure 13). Bundles should not be left out of water
for more than one hour after cutting.
Once "hardened" the fronds should be packaged and maintained
under refrigeration until they reach the retail outlet. Corrugated,
wax coated or wax impregnated cardboard boxes of at least 275
Figure 13. Packing room with fronds on dipping racks which sit upon port-
able bases that are pushed up to a vat of water. They are then
mechanically lifted from the base, transferred into the vat and re-
turned to the base. Fronds are then permitted to drain prior to
packing in shipping boxes.
pound (125 kilogram) test weight material are some of the best
types of containers used by the industry. Twenty or 40 bundles are
then packed in conventional shipping boxes lined with special paper
or perforated polyethylene film liner to conserve moisture and
cushion the contents (Figure 14). Packers should organize bunched
fronds in shipping boxes carefully to minimize mechanical injury to
fronds which causes undesirable blemishes. Boxes should not be
packed so tightly that they bulge excessively. Overfilled boxes
make loading difficult, restrict airflow around boxes and physically
damage boxes and fronds.
Most fern are not harvested, packed and shipped to market the
same day. Therefore, refrigerated storage facilities should be
available to the producer. Packed boxes should be immediately
placed in coolers, maintained at 40 degrees F (4.4 degrees C) and
held until ready for shipment in refrigerated trucks to distribution
points throughout the nation and for export. Leatherleaf fronds
should not be stored for more than a week before shipping, especial-
ly when orders must be shipped long distances. Cut fern have been
held by growers and wholesalers in a few instances for more than 4
weeks without being damaged before reaching consumers, but this
Figure 14. Box of 40 leatherleaf frond bundles in carton lined with polyeth-
ylene film. Fronds must be carefully handled at this point when
lids are closed and stapled to minimize mechanical injury to plant
practice is discouraged. A precautionary disease prevention
measure should be employed when storage of cut fern is necessary.
This usually involves dipping the fronds in fungicide prior to
MARKETING AND SHIPPING
Leatherleaf fern is marketed and shipped throughout the United
States, Canada and many other foreign markets by refrigerated
trucks, ships and airplanes. Most markets in the United States are
located near large population centers.
Many growers ship fern directly to wholesale distributors while
others ship directly to retail florists. A small percentage of the
distribution is through truck sales routes which operate within a
limited distance of production areas. Growers usually find their own
buyers and obtain higher profits than if they sell on prearranged
prices through brokers.
Recently the European market has become increasingly impor-
tant to the Florida cut fern industry. According to statistics re-
leased by the Florida Market News Service for hardy greens and
ferns, 23 percent of the leatherleaf fronds shipped from Florida in
the 1977-78 crop year were exported outside the United States.
Seventy percent of the exported product was carried by ship,
primarily in van containers, and the remaining 30 percent by air
Reliable estimates on leatherleaf shipments have only recently
been collected and published by the Florida Market News Service.
Most cut foliage producers agree that the export market for fern,
especially leatherleaf, has increased rapidly in the last few years.
The European wholesale buyers demand high quality fronds
because the product is exposed to a lengthy process of transport,
distribution and retail handling. The entire process from harvest to
European consumer requires a period of 3 to 4 weeks. Growers and
shippers should provide the best quality fronds possible regardless
of the ultimate market. Factors such as proper conditioning,
packaging, precooling and loading are essential and must be
checked before shipment.
The quality and condition of leatherleaf fern is extremely impor-
tant when it is sold. All fronds should be uniform in size, color and
stage of maturity and free from soil, other foreign material,
diseases, insects and other pests. Shipper and receiver should agree
on size of ferns before shipment because size is important in meeting
specifications of specialized markets of retail florists and tastes of
Consumers expect fronds in floral arrangements to be fresh in ap-
pearance for at least as long as the cut flowers or other greens.
Sometimes, this may be as long as 10 days. Once fronds are placed
in floral arrangements and sold to the consumer they are subjected
to more stress than they sustained during the distribution process.
Pretransit van or van container check
Growers shipping to Europe should become familiar with physical
differences between different models of van containers used by car-
riers. The refrigeration system and other parts of the van must be
functioning properly before ferns are loaded. The thermostat should
be set to 37 degrees F (2.8 degrees C) and the unit should be allowed
to operate through several refrigeration cycles. If the indicating
thermometer on the thermostat varies more than 4 degrees F (2.2
degrees C) from set point, the carrier should be notified so the ther-
mostat can be recalibrated when the van container returns to the
terminal. All doors should close tightly and maintain adequate
seals. Ducts should be installed correctly and function properly.
Floor drains should be free from debris. The inside surface and floor
should be clean and free from undesirable odors. Only the newest
models of van containers should be used for shipping fronds. Per-
sons transporting fronds within the United States and Canada
should check the thermostatic controls of vans in a similar manner
as described for van containers to assure proper cooling or heating
of the cargo.
The stowage pattern in both vans and van containers is the most
important factor in prevention of high temperature or cold damage
to fern during transit. Select a stowage pattern which allows max-
imum use of space and minimum transport cost per unit shipped.
Such a pattern should provide unrestricted airflow through the load
to maintain proper, uniform transit temperatures. Boxes must be
aligned properly and stowed in a manner to prevent movement that
would restrict airflow or increase the risk of physical damage to
boxes and ferns during transit. The type of stowage pattern used
should be determined by size of boxes and inside dimensions of the
van or van container.
Boxes sized 27 by 15 by 5 inches (69 by 38 by 13 centimeters)
should be stacked in van containers in a 5 by 3 modified bonded
block pattern and boxes sized 30 by 21 by 12 inches (76 by 53 by 30
centimeters), 30 by 21 by 6 inches (76 by 36 by 15 centimeters) and
30 by 14 by 9 inches (76 by 36 by 23 centimeters) should be stacked
with parallel channels in the third and fifth layers or sixth layers
(Figures 15 and 16). Since truck vans vary considerably in size and
shape, stowage patterns should be carefully planned for each unit.
Care must be taken to stack boxes adjacent to the forward
bulkhead in all stowage patterns in an arrangement that will allow
free flow of air to the return side of the refrigeration unit. Return air
inlet ducts are at the extreme lower outside corners of the forward
bulkhead in some units. Return air inlets are on the bottom or sides
of an exposed air plenum that projects into the forward cargo area
in some van containers.
If a void remains at the rear of a load when rear doors of a van or
van container are closed, a cargo restraining brace should be used to
hold rear stacks intact and prevent misalignment. Usually boxes in
the extreme rear stack receive the most physical abuse during tran-
The storage temperature during transit should be 34 to 40 degrees
F (1.1 to 4.4 degrees C) (4) and relative humidity 90 to 95 percent.
Figure 15. Recommended stacking of header stack (first stack) for fern box
measuring 30 by 14 by 9 inches. This stacking allows free flow of
air to the return side of the refrigeration unit of thevan container.
Figure 16. Recommended parallel air channel stowage pattern for the fern
boxes measuring 30 by 14 by 9 inches.
The thermostat setting selected for a particular van or van con-
tainer should be based on the outcome of a pretransit vehicle check.
This check will generally indicate that the setting should be 36 to 38
degrees F (2.2. to 3.3 degrees C) if the thermostat is calibrated
reasonably accurately. Temperature controlled vans and van con-
tainers are not designed for precooling, therefore all fern should be
at the recommended storage temperature when loaded.
Distribution and handing of fern after arrival at destination
Vans or van containers should be unloaded immediately upon ar-
rival at their destination. The thermostat in the cold storage room
at the destination should be set between 32 and 34 degrees F (0 and
2.2 degrees C). Deliveries should be made in refrigerated trucks to
other wholesalers or retailers. Ferns should be stored at the recom-
mended temperature after delivery to a wholesaler or retailer until
they are resold or used in floral arrangements. All individuals
-grower, packer, shipper, carrier, importer (when applicable),
wholesaler and retailer-involved in marketing of leatherleaf fern
should do their best to provide proper storage conditions for
leatherleaf, thus insuring consumer satisfaction and a good product
Recording cultural information and yield data will assist growers
in evaluating the impact of specific practices on crop productivity
and frond quality. Growers are encouraged to establish trials to test
new products and new cultural practices on small plots within their
ferneries. Similar plots within a fernery which are not subjected to
the test product or new practice should be used for comparison
within the experimental area. Record keeping is an invaluable tool
whether trials involve fertilizers, pesticides, irrigation systems or
other factors. Accurate records maintained by growers will help
evaluate the worth of new products and/or modified practices.
Figure 17 is a diagnostic form developed to help growers gather
information when problems occur. The form includes most cultural
factors which should be monitored and recorded on a regular basis
even though problems have not developed. It is best to provide in-
formation in all relevant categories of the form if a problem is to be
properly resolved. Often a grower will note an irregularity in the
cultural program or a fluctuation in crop environment which ac-
counts for the problem in question. When a problem cannot be
solved by the grower, this form should be used when submitting
plant problem samples to County Extension Agents.
Time spent keeping accurate records of frond yield, specific
cultural practices and costs of production will provide the pro-
gressive grower or manager with information needed to identify
problems and improve the business. Assistance with costs of pro-
duction in a specific fernery can be obtained through your local
County Extension Agent or Extension Specialist in the Food and
Resource Economics Department, Institute of Food and
Agricultural Sciences, University of Florida, Gainesville, Florida
Figure 17. Commercial leatherleaf fern diagnostic form.
(One form should be completed for each plant problem submitted)
Part A. PRODUCER INFORMATION AND CROP HISTORY
(Producer should complete Parts A & B):
Nursery Mailing address
City County State Zip Code
Contact person Telephone number
Crop Crop age
Symptoms on injury or crop problems:
Distribution of problem: _General _Localized _Scattered
Severity of problem: _Slight _Moderate _Severe
Date problem was first observed:
_Under fabric shade or lath shade
_Under fabric shade + plastic film liner
_Under fabric or lath shade + plastic
film liner + heating
_Under oak shade
_Other (please indicate)
Temperature in Production Area:
Days: to F Nights: to oF.
Figure 17 (continued)
Cold Protection System: (indicate only if injury
occurred during period of cold weather)
No cold protection provided
Overhead sprinkler irrigation
_Open flame burners and return stack heaters
_Forced air heaters (gas or oil)
_Other (please indicate)
Light intensity (foot-candles) or percent shade (estimated):
Growing medium (indicate soil type and amendments used, if any):
Type of Irrigation System:
_Other (please specify):
Once every days (indicate number of days)
Estimated amount of water inches per irrigation
Formulation (granular, liquid, etc.)
Rate Applied (pounds or volume per acre)
Frequency of Application
Micronutrients used (type, rate and frequency)
Liming material used (type, rate and frequency)
Weed Control Program:
_Cultivation of aisles
_Chemical treatment of aisles
and areas around fernery
_Other (please indicate)
Figure 17 (continued)
Pesticide Program: (Insecticides, miticides, fungicides, herbicides &
other chemicals applied to beds or aisles.)
(Material used) (Concentration (Frequency of (Date of last
applied) application) application)
Estimated dollar loss caused by problem to date:
Part B. SOIL TEST REPORT:
(Should be determined prior to referral. Test can be made by
county lab, state lab in Gainesville or commercial lab.)
Soluble salts: (ppm) pH:
Other soil test or water test information, if available:
Part C. WATER TEST REPORT
Soluble salts (ppm) before addition of fertilizer pH
Part D. REFERRALS:
_Problem diagnosed by County Extension Agent
_Sample & copy of diagnostic form referred to State Extension
_Sample & copy of diagnostic form referred to State Extension
_Sample & copy of diagnostic form referred to State Extension
_Sample & copy of diagnostic form referred to State Extension
Cut Foliage Specialist
Part E. DIAGNOSIS AND RECOMMENDATIONS:
Person making recommendation:
GLOSSARY OF TERMS*
Annulus, a specialized ring or partial ring of cells in the sporangium
of some ferns which serves as a mechanism to open the sporangium.
Antheridium (Antheridia), the sperm bearing organ of the
Archegonium (Archegonia), the egg bearing organ of the
Blade, the expanded portion of a frond.
Clone, a group of plants which have the same genetic characteristics
and originated from a single plant by asexual propagation.
Crosier, the young coiled frond.
Epiphyte, a plant which grows upon another plant but is not
Frond, the leaf of a fern.
Gametophyte, that stage of the fern life history which produces the
Indusium (Indusia), the membrane surrounding the sorus.
Pteridology, the science of the ferns.
Pteridophyte, that division of the plant kingdom comprised of
plants that have roots, stems and leaves, but no flowers or seeds.
Pinna (Pinnae), the primary division of a pinnately divided frond.
Pinnule, the secondary division of a pinnately divided frond.
Prothallium (Prothalli), the outgrowth of a spore which is usually
heartshaped and gives rise to both antheridia and archegonia.
Rachis (Rachises), the midrib of a compound frond.
Rhizoid, the root like hairs which develop from the prothallium.
Rhizome, the horizontal stem which is typical of some fern species.
Root, the organ which develops from the rhizome and serves to ab-
sorb nutrients and water for the plant.
Scales, the hair-like or membraneous structures which develop on
the rhizomes and stipes of several fern species.
Sorus, (Sori), an organized group of sporangia.
Sporangium (Sporangia), the sac-like structure which contains
Spore, the single celled structure which gives rise to the
Sporophyte, that stage of the fern life cycle which produces spores.
Stipe, stalk of the frond.
Venation, the pattern of veins in a frond.
*Words in parenthesis are the plural of the preceding word.
1. Conover, C. A. and L. L. Loadholtz. 1970. Leatherleaf Fern
Production in Florida. Ornamental Horticulture Report 70-1.
University of Florida. 26pp.
2. Conover, C. A., R. T. Poole and L. L. Loadholtz. 1979. Up-
date on leatherleaf fern wilt. Agricultural Research Center
Research Report RH-79-1. University of Florida. 6 pp.
3. Harrison, D. S. and C. A. Conover. 1970. Irrigation of
Leatherleaf and Plumosus Ferns. Mimeo Report 70-7.
Agricultural Engineering Department, University of Florida.
4. Miller, W. R., L. A. Risse, T. Moffitt and A. J. Bongers. 1979.
Exporting leatherleaf fern to Europe in van containers. U. S.
Department of Agriculture, Marketing and Research Report
No. 1103. 18pp.
5. Poole, R. T. and C. A. Conover. 1973. Influence of shade,
nitrogen and potassium levels on production and elemental com-
position of leatherleaf fern. Proc. Trop. Reg., Amer. Soc. Hort.
6. Poole, R. T. and C. A. Conover. 1975. Influence of rhizome
type at planting and shade during production on yield of
leatherleaf fern. Proc. Trop. Reg., Amer. Soc. Hort. Sci.
7. Smith, F. B., R. G. Leighty and R. E. Caldwell. 1973. Prin-
cipal Soil Areas of Florida. Bulletin 717. University of Florida
Agricultural Experiment Stations and USDA Soil Conservation
8. 1962 General Soil Map of Florida. University of Florida Agri-
cultural Experiment Stations and USDA Soil Conservation
This public document was promulgated at a cost of $1,198.10,
or 39.9 cents per copy, to inform Floridians about fern produc-
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLOR-
IDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES,
K. R. Tefertller, director, In cooperation with the United States
Department of Agriculture, publishes this Information to further the
purpose of the May 8 and June 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.
HInton, Publications Distribution Center, IFAS Building 664, University of Florida,
Salnesvllle, Florida 32611. Before publicizing this publication, editors should contact
':hs address to determine availability.