Leatherleaf fern production in Florida

Material Information

Leatherleaf fern production in Florida
Alternate title:
Ornamental horticulture report - Florida Cooperative Extension Service ; 70-1
Conover, Charles Albert, 1934-
Loadholtz, Larry L.
Florida Cooperative Extension Service
Place of Publication:
Gainesville, Fla.
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date:
Copyright Date:
Physical Description:
ii, 26 p. : ; 28 cm.


Subjects / Keywords:
Leatherleaf fern -- Florida ( lcsh )
City of Gainesville ( local )
Ferns ( jstor )
Plant roots ( jstor )
Soil science ( jstor )
non-fiction ( marcgt )


General Note:
Cover title.
Statement of Responsibility:
by Charles A. Conover and Larry L. Loadholtz.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
436444767 ( OCLC )


This item has the following downloads:

Full Text

I ,Ornamental Horticulture Report 70 1


JUL 2 0 1972



in florida -

Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville




Appreciation is expressed to the many people who contributed infor-

mation and especially those that reviewed this manuscript on leatherleaf

fern. Without the aid of Dr. J. N. Joiner and Mr. R. D. Dickey, Ornamental

Horticulture Department, Mr. D. S. Harrison, Agricultural Engineering

Department, Mr. J. E. Brogdon and Dr. D. F.'Short, Entomology Department,

Dr. R. S. Mullin, Plant Pathology Department, IFAS, University of Florida,

Gainesville, Drs. W. E. Waters, R. T. Poole and J. F. Knauss, Ridge Orna-

mental Horticultural Laboratory, IFAS, Apopka, Mrs. A. J. Overman, Gulf

Coast Experiment Station, IFAS, Bradenton and Dr. S. A. Alfieri and Mr. G.

W. Dekle, Division of Plant Industry, Gainesville, this information could

not have been assembled.

Table of Contents

INTRODUCTION . . . . . . . . . . . 1

CULTIVARS . . . . . . . . . . . 1

SITE SELECTION . . . . . . . . .. . . . 2

LIGHT REQUIREMENT . . . . . . . . .. . . 4

STRUCTURES . . . . . . . . .. . . . . 4

SOIL PREPARATION . . . . . . . . . . . 7

PLANTING . . . . . . . . .. . . . ... .9

FERTILIZATION . . . . . . . . .. . . . 10

IRRIGATION . . . . . . . . .. . .... .. 15

TEMPERATURE CONTROL . . . . . . . . ... ... .15

WEED CONTROL . . . . . . . . ... . . .17

NEMATODE CONTROL . . . . . . . . .. . . .18

INSECT CONTROL . . . . . . . . . . . .21

DISEASE CONTROL . . . . . . . . . . . 22

ANIMAL AND RODENT CONTROL . . . . . . . ... .25

HARVESTING . . . . . . . . ... . . . .25

MARKETING . . . . . . . . ... . . . . 26




Charles A. Conover and Larry L. Loadholtzl


Florida leads the United States in production of leatherleaf fern,

with approximately 1000 acres in production. Estimated value of the 1969

crop was about 7 million dollars. This did not reflect the true potential

of 1000 acres since at least 25 percent had been planted less than one year.

Small amounts of leatherleaf fern were produced in Florida during the

1930's and 1940's, but major plantings were not started until the early 1950's.

The rapid production increases are not related to improved methods of produc-

tion, but to a change by commercial florists from Asparagus plumosa plumosaa

fern) to leatherleaf fern in their floral arrangements. This change is due

primarily to the better keeping quality of leatherleaf fern, and to a change

in consumer preference concerning leaf shape and texture.

The main production area for leatherleaf fern is Volusia County, but

considerable production also occurs in Putnam, Lake and Orange counties.

Small plantings of leatherleaf fern can be found throughout Florida on sandy,

well-drained soils, even in northern sections when winter production is provided.


The commercial leatherleaf fern grown in Florida is Polystichum

adiantiforme, and is a rhizomous herb native to tropical areas of South

Assistant Ornamental Horticulturist, Cooperative Extension Service, University
of Florida and Ornamentals Extension Agent, Cooperative Extension Service,
Volusia County.

America, South Africa and New Zealand. There is much confusion within the

industry concerning cultivars and growers generally acknowledge three dis-

tinct types. This is probably true, but botanical nomenclature does not

substantiate these observed differences.

Grower-named cultivars of leatherleaf generally associated with quality

fern are the selections 'Baker' and 'Mayfield'. These selections both

produce fronds that are heavy, have large sturdy mid-ribs and a deep, dark,

glossy green color. However, even these better selections will be of poor

quality unless proper growing conditions are provided.

There are two less desirable selections of leatherleaf fern grown by

a few producers. 'Curley leaf' has curly fronds and poor color which does

not sell well. The other less satisfactory selection 'Light stem' is

characterized by light weight stems which have little substance, poor color

and rapid growth. Due to poor stem rigidity and other factors it does not

have the market demand typical of 'Baker' and 'Mayfield'.

Leatherleaf fern used for planting stock should be of the 'Baker' or

'Mayfield' selections. Fern with curly or light-weight fronds, poor rigidity

or poor color should not be used for planting stock, no matter what the



Leatherleaf fern can be grown from Jacksonville south, but warm loca-

tions should be selected or provision made for protecting plants during cold

weather. Mature fronds are injured when temperatures drop below 280F., even

though rhizomes survive lower temperatures. Except for small protected

plantings for local sales the northern limit for commercial plantings is

south of an east-west line through Ocala and Palatka, Florida.

High, sandy, well-drained soils 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 it cannot tolerate standing water or saturated

soils for more than 6 to 12 hours without damage. Rapid internal and sur-

face drainage necessary for production of leatherleaf fern is usually

associated with soil types 1, 2, 3, 4, 5, 8, 9, 12 and 17. (See general

soil map of Florida 1962 available from the soil conservation service).

These sandy soils are moderately to excessively drained and can be used

without need for ditching and tile drains. Even in these soil types areas

that form pockets without surface drainage to lower areas should not be used.

Soil types 1 and 2 have lower water and nutrient holding capacities and

therefore are less satisfactory than other types unless amended. Leather-

leaf plantings are also successful on sandy lower elevation soils when they

are tile drained.

Leatherleaf fern requires shade for quality production and, until

recently, many growers selected sites with natural oak shade. This is

initially a low-cost source of shade, but long-run costs are increased

because of pruning, plant competition, insect problems, pesticide toxicity

to trees and obstacles to mechanization. Therefore, even though natural

oak shade might be acceptable for small plantings it is not recommended for

large plantings.

Other factors of importance in site selection include land cost, labor

availability, transportation and a good water supply.

Future growth of the leatherleaf fern industry in Florida will continue

in Volusia, Putnam, Lake and Orange counties because most requirements of

site selection can be easily obtained there. However, other areas that can

provide many of the necessary requirements include parts of counties along

the central and southeast coasts, from Orlando to Lake Placid in the ridge

section and in parts of counties on the west coast south of Dunellon. Small

plantings for local sales can be located wherever well-drained soils can be



The exact light level required for production of leatherleaf fern has

not been determined because it is influenced by fertilizer and watering rates.

In general, fern grown under heavy shade (80% or more) will develop a dark,

green color and a flat leaf on fairly low fertility regimes, but production

will be low. Fern grown under medium shade (65 to 70%) requires higher

fertility levels to obtain the same color, but quality and production will

be higher. Fern grown under less than 60% shade will be light green and

fronds tend to be thick and curly. Considering light levels in Florida on

a yearly basis the best percent actual shade to provide is about 65 to 70

percent. Determination of shade levels provided by oak tree shade is diffi-

cult, and is best done with the aid of a light meter capable of reading in

foot-candles. Table 1 provides approximate maximum obtainable light levels

in foot-candles under saran or polypropylene shade during different seasons.


Structures will include all methods of providing shade for leatherleaf

fern including trees, brush covered sheds, slat sheds, and saran and poly-

propylene covered shade houses. Each method of providing shade has some

advantages and disadvantages. Irrigation is necessary with all growing

structures and is discussed in the irrigation section.


Tree shade -- At present about 50% of leatherleaf fern production

is under oak shade, but this method is decreasing. A site shaded by trees

has the disadvantage of competition from trees for water and nutrients,

and in addition they serve as obstacles to mechanization, use of herbi-

cides, fumigants and some types of heating systems. Shade provided by

trees is variable and cost of pruning and damage to ferns during pruning

is high. Almost all new ferneries being established do not use trees for

shade. When trees are used for shade they should be pruned during summer

months to obtain an average of 3000 to 4000 foot-candles of light at noon.

Slat sheds -- A considerable amount of leatherleaf fern is grown

under slat sheds, primarily because it has replaced plumosa fern. Cost

of materials and labor has made construction of new slat sheds expensive

for production of leatherleaf fern, but these sheds do provide an excellent

source of shade. When new sheds are built or old ones repaired, slats

should be spaced to provide about 65 to 70 percent shade or 30 to 35 percent


Brush covered sheds -- Many sheds covered with rosemary (Ceratiola

ericoides) can be found in the fern producing areas. These sheds create a

fire hazard, especially during winter months if open flame heaters are used

around the fernery, since rosemary contains a volatile oil. Few new sheds

being constructed use this material since it is scarce near fern-producing

areas and is expensive to gather. Sheds built for covering with rosemary

have posts set 10 to 12 feet apart, with 1 x 4 or 2 x 4 inch lumber stringers

tying them together at the top. The structure is then covered with gal-

vanized chicken wire of about 2 inch mesh and rosemary placed on top of the

wire, until the desired shade level is obtained.

Saran and polypropylene shade houses -- This type of construction is


most common in new ferneries and in additions to old ferneries where

expansion is occurring. Initial costs are higher than some of the other

methods of shading fern, but it pays off with time in reduced operating

costs and improves yield and quality. In addition, this type structure is

easy to cover with plastic during winter months for cold protection.

Construction of saran or polypropylene shade houses is basically the

same as other type sheds, but growers use minor variations in post spacing,

lumber type and size. Generally, 10 to 12 foot long posts are spaced ap-

proximately 10 to 12 feet or more on centers and tied together at the top

with 1 x 4, 2 x 4 or larger stringers. Size of the stringers depends on

post spacing; 2 x 4 inch stringers are satisfactory for 12 foot spacings or

less, but heavier lumber must be used with wider post spacings. Another

method of construction utilizes posts on the same spacing, but instead of

stringers the posts are tied together with heavy galvanized wire of about 8

gauge. The shade cloth is attached either to wood stringers with tack-strips

or to wire with nylon cord or S-hooks.

Table 1. Approximate maximum obtainable foot-candles of light received under
various percentages of shade during different seasons in Florida.1

Season of year
Actual shade Winter Spring Summer Fall
provided (Dec.-Jan.-Feb.) (Mar.-Apr.-May) (June-July-Aug.) (Sept.-Oct.-Nov.)
(Full sun) 8,700 15,300 15,900 11,600
50% 4,350 7,650 7,950 5800
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

1Weather forecasting Service, Gainesville, Florida



Clearing -- When fern plantings are to be made utilizing oak shade,

underbrush, stumps and pine trees should be removed. Removal of pines during

the clearing phase is easier than removal later, after they have died from

high fertility levels necessary for growth of fern or disease or pesticides.

Modern production methods are not adapted to oak shade ferneries, and there-

fore, complete clearing is recommended rather than the above procedure. The

trees, stumps and brush should be burned in an area that will not be immedi-

ately planted to fern due to high levels of some fertilizer elements in the


Soil amendments -- Use of well drained, sandy soils for fern production

creates problems with maintenance of proper soil moisture and nutritional

levels. Amendments are used to improve soil physical condition, aeration,

and moisture and nutrient holding capacities. Amendments are grouped as in-

organic and organic. Inorganic amendments include calcined clays, perlite

and vermiculite, although they do not decompose in the soil, they are too

expensive for use in fern production. Organic amendments easily obtained in

Florida include bagasse, peat moss, garbage compost, shavings, sawdust and

pine bark. Local availability and cost per cubic yard usually determine

feasibility of using a particular amendment. Amendments containing high

levels of cellulose, such as sawdust, shavings and pine bark, will have to

be supplemented with nitrogen to prevent tie-up of available nitrogen in the


Organic amendments are suggested for us- in fern plantings and a 1 1/2

to 2 inch layer should be added to planting beds and rototilled to a depth of

6 inches. Average particle size of the amendment used should allow good

drainage and aeration when mixed with native soil.

Leatherleaf fern can be grown in sandy soils without the addition of

soil amendments, but high quality fern is more difficult to produce under

these conditions. The low "buffer" capacity in the soil causes large

changes in pH and soluable salts from the addition of fertilizers. Ferti-

lizer programs must be designed to supply small amounts frequently, since

sandy, non-amended soils are less retentive of fertilizer nutrients.

Watering is also more critical in non-amended soils, as less water is held

for plant growth and more frequent irrigation is necessary, further compli-

cating the fertilizer retention problem.

Needed calcium, magnesium, phosphorus and micro elements should be

mixed into the soil with the soil amendment. Most virgin Florida soils need

at least 2,000 pounds of dolomite and 1,100 pounds of superphosphate per

acre (4 1/2 lbs. dolomite and 2 1/2 lbs. superphosphate per 100 sq.ft.) to

add calcium, magnesium, phosphorus and sulphur. In addition, 25 pounds

copper sulphate, 25 pounds zinc sulphate, 50 pounds manganese sulphate and

25 pounds iron chelate should be added per acre to amended virgin soils. A

micro element mix may also be used, provided rates are similar.

In order to determine quantities of dolomite and superphosphate nec-

cessary for soils already in cultivation and for more accurate recommendations

on virgin soils, samples should be taken to determine initial levels of

these elements. The most desirable pH is in the range of 5.5 to 6.0, there-

fore, if pH is below 5.0, add 1/2 to 1 ton of dolomite per acre. Based on

the ammonium acetate procedure of soil analysis used by the University of

Florida, where calcium levels in the soil are low and pH is high, use calcium

sulphate (gypsum) to raise the calcium level to at least 1000 pounds CaO per

acre. Soil magnesium level should be at least 250 pounds MgO per acre and

phosphorus at least 50 to 80 pounds P205 per acre. Soil amendments, liming


materials and superphosphate should be thoroughly incorporated into

planting beds to a depth of 6 to 8 inches.

Soil fumigation Fumigation of planting areas is not recommended

at the present time due to lack of information on this aspect of pro-

duction. Growers who might desire to establish a trial planting on fumi-

gated soil for disease, nematode and weed control may use methyl bromide

at 1 1/2 to 2 pounds per 100 sq. ft. or Vorlex-201 at 1/2 to 2/3 gallon per

600 sq. ft. Be sure to follow label directions on waiting period prior to

planting previously dipped fern rhizomes or nematode free fern.


After soils are amended and rototilled, planting beds should be oriented

in a north-south direction and elevated about 4 to 6 inches above aisles to

aid drainage. Beds should not be wider than 4 feet to aid in maintenance

and help prevent workers from walking in beds which damages fern and causes

disease spread. Bed widths of 3, 3 1/2 and 4 feet are commonly found in the

industry with the narrower beds being most popular. Aisle widths also vary,

but 2 1/2 to 3 foot aisles seem satisfactory.

Plant spacing within beds is usually 12 x 12 inches, but some growers

utilize a spacing of 18 x 12 inches. The wider spacing is more conservative

of planting material and delays the time when overcrowding will occur, how-

ever, production will be lower the first 1 to 2 years. Production infor-

mation is not currently available on the various spacing systems used.

Plants should be planted approximately 1 1/2 inches deep, as deeper plant-

ing causes delay in establishment and shallow plantings dry too easily.

Plantings should be established with the best quality rhizomes

available. Planting stock should have rhizomes 4 to 5 inches in length with

2 to 3 healthy fronds and an uninjured terminal bud. Larger clumps with


2 or more rhizomes may be used for more rapid establishment if planting

stocks are available at low cost. Fern grown from spores should not be

used, due to variation between plants (such plants probably will not be

of the 'Baker' or 'Mayfield' type) and because it takes about 3 years for

spores to produce plants large enough for fronds to reach cutting size.

Damaged fern rhizomes can be saved and disked or set in a nursery block

where they will make satisfactory planting stocks after about 1 to 2 years.


Leatherleaf fern is produced in Florida under many fertilizer regimes,

but proper fertilization programs will improve quality, lengthen keeping

time in the home and produce high yields per square foot. Rates of ferti-

lization should be varied depending on light levels, type of soil and type

of shade. More information needs to be obtained on leatherleaf fern ferti-

lization and the best available is presented. Table 2 provides information

on foliar nutritional levels associated with leatherleaf fern. Granular

fertilizers applied overhead may cause foliar injury if applied to wet

foliage. Therefore, they should be applied to dry foliage and the residue

washed from fronds as soon as possible. Fern should be irrigated overhead

for about one hour to move fertilizer into the root zone.

Fertilizer sources -- Several types of fertilizers, including inorganic,

organic and slowly soluble or slow-release fertilizers are available. In-

organic sources of fertilizer are recommended because they are readily a-

vailable, low in cost, and easy to apply through irrigation systems or with

mechanical distributors. Where fertilizers must be applied by hand, organic

or slow-release forms are recommended during warm months to conserve labor.

Availability of nutrients in organic fertilizers depends upon environmental

factors such as soil temperature, moisture and microbial populations.


Table 2. Chemical composition of mature leatherleaf fern fronds based
on dry weight giving low, desirable and high ranges of elements.

Low High
Element (less than) Desirable range (more than)
% % %
Nitrogen 2.0 2.2 to 3.0 3.2
Phosphorus 0.2 0.25 to 0.50 0.6
Potassium 2.3 2.5 to 3.8 4.0
Calcium 0.25 0.30 to 0.80 1.0
Magnesium 0.28 0.20 to 0.40 0.5

ppm ppm ppm
Boron 20 25 to 75 100
Copper 8 10 to 30 40
Iron 75 100 to 200 250
Manganese 25 50 to 150 200
Zinc 20 25 to 100 150

These averages have been obtained by sampling good and poor quality fern,
and is a compilation of information from analysis by the Ornamental
Horticulture Department and International Minerals Corporation.

Fertilizer ratios -- Proper fertilizer ratios depend on previous ferti-

lization practices. Generally, phosphorus accumulates in sandy soils with

a pH in the range of 5.5 to 6.5 and is needed by plants in lesser amounts

than nitrogen and potassium. On land where the residual phosphorus level

is not too high a 2:1:2 ratio fertilizer can be used such as 8-4-8. Gener-

ally, this ratio is satisfactory as long as phorphorus does not accumulate

and interfere with micro element uptake. Soils with high phosphorus levels

(above 150 pounds P20 /A) should be fertilized with materials having a 1:0:1

ratio or close to it such as 8-0-8 or 20-2-20. Some virgin soils with low

pH levels (below 5.5) may be low in phosphorus and a 1-1-1 ratio fertilizer

such as 8-8-8 or 20-20-20 may be used until phosphorus levels increase.

Fertilizer rates -- Recommended rates are determined by rate of plant

growth, light level and other environmental factors. Fern growing under

light levels recommended in this publication (approximately 3000 to 5000

foot-candles depending on season) should receive more fertilizer than fern


growing under 2000 to 3000 foot-candles. Therefore, rates listed in Table

3 can be reduced by 25 to 30 percent if fern is grown under heavy shade

(approximately 80%). Leatherleaf fern grown on sandy, unamended soils and/or

under oak-tree shade where more competitive growing conditions exist should

receive the higher rate listed in Table 3. Generally, the fertilizer rate

should be decreased from 30 to 50 percent during the winter months (December

through February) when low temperatures prevail and growth is reduced un-

less protected and heated.

Table 3. Fertilizer recommendations for leatherleaf fern
60 to 70 percent shade

grown under

Fertilizer Rate Rate
element Ibs/acre/month lbs/1000sq.ft./month Remarks






50 to 60

25 to 30

50 to 60

as needed


1.2 to 1.4

0.6 to 0.7

1.2 to 1.4

as needed


Use sources to pro-
vide 1/2 in ammon-
ium and 1/2 in nitrate

Use a lower rate if
soil level is high.

A high chlorine con-
taining source is
not recommended.

Apply once or twice
a year to maintain
1000 to 1500 lbs
CaO per acre.

Apply monthly, or
at 6 times this
rate once each 6

Microelements -- Exact levels of microelements required by leatherleaf

fern are not known at present. However, fern deficient in iron and manganese

has been found in a number of ferneries where they have not been soil incor-


porated. In some growing areas, it will be necessary to use fertilizers

containing microelements, but continual use is not recommended due to increased

cost and possible build-up to toxic levels in soil. Growers should remember

that microelements such as iron, manganese and zinc may be included in fungi-

cidal sprays and adjust microelement fertilization accordingly.

Soluble salts -- Leatherleaf fern is intolerant of high soluble salt

levels in the soil. Injury occurs first to roots and is characterized in

above ground portions of the fern by temporary wilting of young fronds, margi-

nal burning of young or recently matured growth and various chlorosis patterns

indicative of microelement deficiencies.

Factors affecting soluble salt level includes watering practices,

salinity of water and fertilization programs. Method of watering and soil

moisture levels affect soluble salts, and where salinity is a problem high

soil moisture should be maintained. Medium to high soil moisture reduces

salt concentration, for example, a soil containing 500 ppm soluble salts at

50% soil moisture will contain approximately 1,000 ppm soluble salts at

25% soil moisture. To prevent possibility of damage from soluble salts,

leatherleaf fern should never be allowed to become too dry, especially if a

high fertility program is followed.

Irrigation water containing large amounts of soluble salts should not

be used for watering leatherleaf fern, but water with salt levels as high as

800 ppm can be used provided sufficient leaching occurs each time the crop

is watered. Irrigation water with 500 ppm soluble salts or less are considered

best for leatherleaf fern production.

The last primary source of soluble salts is an incorrect fertilizer

program. Sources of various fertilizers and essential elements are almost

always salts, such as potassium nitrate and ammonium nitrate. When such salts


are added to the growing medium the osmotic (salt) concentration of the

soil solution increases. If this concentration exceeds the osmotic con-

centration of plants cells comprising absorbing root hairs, water will be

withdrawn from the roots. Therefore, the fertilizer program must supply the

right amounts of fertilizer at sufficient frequency to prevent application

of too much atd at one time.

Growers having excessive soluble salt levels in their growing medium

should take corrective measures as soon as possible to prevent damage to

their fern. Irrigate heavily to immediately lower soluble salts to a level

that can be tolerated. Amounts of water needed depend on the degree to

which soluble salt level is to be reduced. Generally, for each square foot

of soil to be leached six inches of irrigation water leaches out one-half of

the salt and 12 inches four-fifths of the salt.

Red-edge -- This problem is due to a calcium deficiency in leaf tissue,

and is corrected by maintenance of proper soil calcium levels. Soil calcium

level should be maintained at about 1000 pounds of CaO per acre to prevent

this deficiency from occurring -- additional information on calcium levels is

given in the soil amendment section and in Table 2.

Red-edge can be corrected quickly on developing fronds by application

of 5 pounds of calcium nitrate per 100 gallons of water sprayed per acre of

fern. However, addition of calcium to the soil will be necessary to obtain

permanent control and weekly foliar applications will be necessary until soil

calcium is available. Application of calcium will not improve the condition

of old fronds, but new fronds should develop normally.

Red-edge type symptoms can be caused by other factors including nutrition,

soluble salts and other abnormalities, but these are generally brown, rather

than reddish.



Irrigation of leatherleaf fern is necessary to produce quality crops,

since water stress in a plant -- even if it occurs for a short time --

reduces growth. The amount of water to apply depends on soil type, shade

level, humidity, wind speed and temperature. Generally, one inch per ap-

plication is necessary during hot summer months. Frequency of irrigation

and amount of water to apply each time must be adjusted to keep soil moist,

not saturated to the depth of the root system. Watering lightly and fre-

quently leaves soil in the lower root region dry and reduces root and top

growth, while over-watering leaches fertilizer from the root zone.

Overhead irrigation is the best method of applying water to leatherleaf

fern. Such systems should be set up to obtain a 100 per cent over-lap, so

that they will also be satisfactory for application of liquid fertilizers and

as an aid in cold protection. Generally, ferns require an average of one

inch of water every 3 days during summer months and one-half inch every 4 days

during winter months when growth is restricted and temperatures low.

Complete information on overhead irrigation systems for leatherleaf

fern can be found in Cooperative Extension Service Engineering Mimeo Report

63-2, (Revised), "Irrigation Design for Leatherleaf and Plumosus Fern in

Florida". Copies are available from your Cooperative Extension Agent.


Leatherleaf fern is not injured until temperatures in the fernery

drop below 30"F. Numerous methods, such as various types of oil heaters,

open fires and sprinkler irrigation are used to protect ferns from freezing.

Each method has advantages and disadvantages.

Open flame oil heaters such as the open furnace, single cone and

return stack types provide some protection, but cause considerable fern


damage during filling operations, and are dangerous to structures. This

method is still being used in a number of operations and is better than no

protection at all.

Research has shown recently that leatherleaf fern could be protected

with sprinkler irrigation by utilizing the latent heat of fusion. When

liquid water turns to ice, 80 gram calories of heat are released per gram of

water and if water application'is continuous during the freezing period the

constant release of this heat will maintain temperature of the fern frond

at approximately 320F. Low angle, double headed sprinklers must be used,

the supply of water must be constant, and at least 0.3 acre inches of water

must be supplied each hour for this system to work properly. The irrigation

system must be started when the temperature is 32 to 340F. and continuously

operated until ice from the freeze has melted or the wet bulb temperature has

reached 320F or greater.

Sprinkler irrigation used for freeze control is effective and fairly

economical, but has a number of disadvantages. If the irrigation system is

not operated continuously throughout the freezing period fern damage may be

greater than if the sprinkler system was not used. This occurs when foliage

with ice reach the "wet bulb" temperature which may be 2 to 10 degrees F

below "dry bulb" temperatures due to evaporational cooling. Increased damage

may also occur if insufficient water is applied to keep up with the amount

that is freezing. Application of large amounts of water necessary to prevent

freeze damage during severe freezes may cause serious root and rhizome damage,

soil erosion, destroy soil structure and leach nutrients out of the root zone

including phosphorus, calcium and magnesium as well as nitrogen and potassium.

Therefore, this method of cold protection is decreasing in popularity with

some growers.


Covering ferneries with lightweight two mil. polyethylene is the most

recent and best method of protecting leatherleaf fern from frost. This

method is also useful in increasing production during winter months when ferns

bring the best price. Polyethylene is applied inside the fernery by tacking

it to sides of stringers between posts and pulling it tight. While poly-

ethylene is still in the roll 1/2 inch holes should be made about 12 inches

on centers with an electric drill, this will allow rain water to run through

and prevent water pocketing which can destroy the structure. Polyethylene

should be attached inside the growing structure about the middle of November

and removed during late March. High day temperatures inside the fernery

can be controlled by attaching polyethylene to outside walls so that it can be

rolled up during high-temperature periods to allow ventilation. Loss of heat

through the holes is negligible, but additional heat is sometimes necessary

to prevent freezing during severe cold and to obtain good winter production.

Many sources of heat can be used satisfactorily, but LP or natural gas, if

free from impurities, seems the best heat source. In addition, these

sources provide CO2 as well as other impurities. The disadvantages to covered

structures are cost of polyethylene, labor and heating costs. However,

increased winter production due to lack of frost problems and more favorable

growing temperatures offset these costs and guarantee a steady supply of fern.


Cultivation is still a good method of controlling weeds in young

leatherleaf plantings since fern that is not established is more easily in-

jured by herbicides. Any measure that will aid in preventing contamination

of planted areas with weed seed should be practiced. To control weeds that

germinate during the first 6 months light cultivation in aisles with roto-


tillers and within rows with small "sweep-type" cultivators or hoeing

is suggested.

At the present time, no herbicides (chemical weed killers) are regis-

tered for use on leatherleaf fern plantings. However, Simazine has been

used for a number of years with success in a large number of ferneries.

Simazine has been applied at the rate of two pounds of active ingredient

per acre, but should not be applied to fern until 6 months after planting

and then not more than once every 6 months. Granular Simazine has proved

most satisfactory and can be used in any type of fernery, including those

under oak shade. Misuse of Simazine will cause stunting of leatherleaf

and, therefore, the listed rate should never be exceeded.

Paraquat, a contact herbicide that kills green vegetation that by

contact can be used for spot or aisle treatment if a directed spray is

used to prevent contact with fern. This material has been used with satis-

factory results at a rate of 1/2 pound active ingredient per acre. For

small areas, 2 teaspoons of Paraquat per gallon is effective. Do not allow

inexperienced labor to use Paraquat because drift or contact with fern will

cause brown spots on foliage, and the chemical can be dangerous to the user.


A lesion nematode, Pratylenchus penetrans, is a major problem of

leatherleaf fern in Florida. These microscopic worms seriously injure roots

and rhizomes and may predispose plants to attack by soil-borne disease

organisms. Root injury is frequently so serious that heavy nematode infes-

tations may reduce frond production by 50 percent or more. Nematode in-

fested leatherleaf fern is characterized by poor color, small sized fronds

and slow growth.


Nematodes can be controlled in bare soil by fumigation, but this is

not recommended unless clean planting stock is used, since nematode popu-

lations have been shown to increase more rapidly in fumigated than non-

fumigated soils. Nematode reinfestation of nematode free fern beds may occur

from contaminated planting stock, dirty tools and movement of infested soil

into planted areas and migration through soil. Two methods of nematode con-

trol to eliminate the possibility of reinfestation are: 1--pre-plant bare

root dips to reduce the possibility of planting contaminated stock and 2--

post-plant soil nematicidal application to kill nematodes that have become

established in planted areas.

Control of Nematodes on Leatherleaf Planting Stock In experimental

studies the materials listed in Table 4 have provided satisfactory control

of nematodes present on or in roots and rhizomes. Planting stock should be

cleaned and prepared for planting prior to dipping in chemical solutions to

prevent dipping unnecessary material. Fern should remain submerged in the

dip for 15 minutes before being removed and allowed to drain. Except for

zinophos, none of these materials have label registration and are suggested

only for trial.

Table 4. Nematocidal dips for control of Pratylenchus penetrans in
leatherleaf planting stock.

Chemical lbs. active ingredient Remarks
per 100 gallons
MoCap 1/4 No label registration at
present. However, one should
be granted in the near future.

Nemacur 1/5 No label registration.

Parathion 1/4 No label registration. Due
to high toxicity of this
material proper application
precautions should be taken.
Zinophos 1/4 See label for correct usage.


Control of Nematodes in established Leatherleaf Plantings Frequency

of application of nematicides to stock beds vary because this depends on

level of original infestation, sanitation practices and many other factors.

The best procedure is to take a nematode sample, have it analyzed and treat

if the level of nematodes is sufficiently high as to reduce production. Except

in extreme cases, more than one application a year is not recommended.

Application procedures depend on the nematicide formulation. Granular

materials can be applied broadcast to the soil surface, whereas liquid

materials should be mixed with a small amount of water and sprinkled on the

soil surface. Immediately after application of granular materials, they

should be raked into the surface and then one-half inch of water should be

applied over granular or liquid applications. Rates and materials listed

in Table 5 applied over fern have not caused injury and have controlled lesion

nematodes in experimental tests. Except for zinophos, they are listed only

for trial.

Table 5 Nematocides for control of Pratylenchus penetrans in established
leatherleaf fern plantings.

Chemical active ingredient per Remarks
Furadan 10 No label clearance at

MoCap 10 No label registration at
present. However, one
may be granted in the near

Zinophos + Thimet 4 + 4 Due to high toxicity
of this material proper
application precautions
should be taken.



Insect pests of leatherleaf fern can be a serious problem if allowed to

increase to high levels, therefore, many growers normally include an insecti-

cide in their spray mixture when spraying for disease control. Inclusion of

an insecticide in the spray tank each time plants are sprayed for disease con-

trol is generally unnecessary, except during periods of the year when leaf-

hoppers and caterpillars are a problem unless visible evidence of insects are

present. Thrips are thought to be a serious problem in the spring in ferneries

under oak-tree shade. Although injury to fern fronds does occur, no one has

proven that thrips in the oak flowers that drop from the trees are the cause

of the injury. The possibility exists that injury may be caused from tannic

acid leaching from the flowering oak tree catkins. Insect pests which may be-

come a problem on leatherleaf fern are listed in Table 6, with suggested con-

trol materials.

Table 6. Insect pests and control materials for leatherleaf

Pest Insecticide Formulation

Caterpillars Carbaryl (Sevin) 50% WP
Toxaphene 8 E
Grasshoppers Toxaphene 8 E
Leafhoppers Dimethoate 2.67 E
Thiodan 2 E
Leatherleaf Thiodan 2 E
fern borer or
Ca caterpillar) Diazinon 4 E
Spider mites Chlorobenzilate 25% WP
Tedion 25% WP
Kelthane 18.5 E
Thrips Dimethoate 2 E
Lindane 25% WP
Termites Chlordane 8 E
Slugs and Metaldehyde dust 15% dust
snails or bait
1 WP = Wettable powder, E = Emulsifiable concentrate


Amount per
100 gallons
of water
2 pounds

1 1/2 pints
1 1/2 pints
1 pint

2 pints
2 pints

2 pints
1 pound

1 pound

2 pints
2 pints

1 pound
1 pint





Control of fungal diseases of leatherleaf fern grown under con-

ditions of high humidity and temperature is difficult, especially during

the rainy summer season. Factors having direct effect on success of a

disease control program include the chemical used, frequency of spraying,

adequate spray pressure, proper type nozzles and adherence to good sani-

tation procedures.

Spray schedules How often to spray depends on the initial disease

severity coupled with the continuation of favorable environmental conditions

(rain, temperature, etc.) conducive to disease development. Since the

presence of tree moisture is necessary for the development of all known fern

diseases the length of time the plants stay wet is extremely important.

Leatherleaf fern density is important in this respect since it directly af-

fects humidity and may cause foliage to remain wet for long periods. One

spray application every 2 weeks or month may protect plants in dry weather

when a low level of inoculum are present, and environmental conditions are

poor for disease development, but spraying every week or few days may be

necessary during cloudy, rainy weather when all factors which promote a

high incidence of disease are present. A fixed spray schedule is not

suggested, because during dry weather too much spray residue and possible

injury may result, whereas during wet weather too little protection may

be available.

Spray coverage Spray pressure should be high enough to obtain

good coverage and without injuring newly expanding fern fronds. Proper

nozzle arrangement for the pressure being used can be obtained through trial

and error and by observing sprayed fronds and making adjustments until

coverage is satisfactory. Poor disease control can frequently be traced to

poor spray coverage, especially on undersurface of fronds. Growers employing


irrigation systems instead of power sprayers for chemical application

should remember that this method is not recommended, and results in very

poor coverage on the under-side of fronds. This method may be satis-

factory during periods when possibility of infection is low, but will be

inadequate during periods conducive to rapid disease development. Addi-

tionally, it is very difficult to control properly disease organisms that

have become established if complete coverage of both top and under-sides

of fronds is not obtained with the chemical spray.

Concentration of chemicals Too often the tendency is to use a

higher concentration of fungicide than recommended when a serious disease

problem develops. Better disease control, however, is obtained by in-

creasing gallonage to assure coverage and frequency of spraying. Fungi-

cides are not like insecticides; they function as protectants, not era-

dicatants, and their maximum protection will result when the proper rate

is properly applied.

Sanitation Leatherleaf planting stocks are frequently a source of

disease producing organisms for the rest of the operation. New planting

stock must be healthy and diseased plants should be destroyed or removed

completely from the growing area. Even the best spray program is often in-

capable of preventing disease losses with the presence of abundant spores

from diseased plants being dispursed in wet weather.

Disease problems of leatherleaf fern can be classed as root and stem

rots and fungus leaf spots. Control methods for diseases found in each area

are different. Much more information from research is needed on diseases of

leatherleaf fern and their control.

Root and Stem Rots Loss of plants and growth reductions caused by

root rots are not known to be common in leatherleaf fern production but may

be more serious than now realized. Serious problems have occurred in some


ferneries, especially where root damage from excess water or fertilizer had


The most common fungus root and stem rots of leatherleaf fern are

caused by species of Pythium and Rhizoctonia. Symptoms of infection caused

by Pythium occur as blackening and water soaking of plant roots. Infection

usually occurs at root tips and progresses through roots to the rhizomes

causing them to collapse. Rhizoctonia causes a dry, brown, lesion type of

rot occurring anywhere on roots or rhizomes, but most frequently attacking

near the junction of fronds and rhizomes. Suppression of root rots may be

obtained by drenching plants and soil with chemicals listed in Table 7.

Table 7. Drench recommendations for control of leatherleaf root and stem rots.

Disease Amount per Frequency
Organism Fungicide Concentration 100 gallons of
of water Application

Pythium Dithane M-45 80% WP 2 pounds Every 1-2
or months.
Dexon 70% WP 1/2 pound "

Rhizoctonia Dithane M-45 80% WP 2 pounds Every 1-2
or months.
Fermate 76% 3 pounds As needed.

Fungal Leaf Spots A number of leaf spots have been identified on

leatherleaf fern and these as with other disease problems are most likely to

occur during wet, humid periods.

Generally, most fungal leaf spots start as pinpoint lesions which are

regular in outline. Leaf spots may have gray to reddish brown centers with

darker margins or of a uniform color. As spots enlarge they frequently coalesce

to form large lesions. Diseases most commonly associated with leaf spots on

leatherleaf fern are caused by the fungi Cylindrocladium and Cercospora.


Control of fungal leaf spots may be obtained with materials listed in

Table 8.

Table 8. Control recommendations for fungus leaf spot control on leather-
leaf fern.

Amount per
Disease 100 gallons
Organism Fungicide Concentration of water

Cercospora Daconil 75% WP 1 1/2 pounds
Cvlindrocladium or
Rhizoctonia Manzate D 80% WP 1 pound
and others or
Dithane M-22 Spec
Benlate 50% 1/2 pound-label
or clearance unclear
at this time
Zineb 75% 1 1/2 pounds


Armadillos, skunks, salamanders and moles have become destructive to

leatherleaf fern plantings in some areas, especially those in or near large

wooded areas. Damage occurs at night when these pests dig or root-up plants

while searching for soil-borne insects and worms.

The easiest way to eliminate these pests is to eliminate the food

supply. Chlordane or Aldrin can be used to kill soil-borne insects, and

is most effective when soil incorporated to a depth of 6 inches. However,

surface application is also beneficial. Chlordane should be applied at 5

to 6 pounds active ingredient per acre and Aldrin at 3 to 4 pounds active per

acre. Traps for salamanders and moles are also available.


Leatherleaf fern is harvested with hand labor and there does not appear

to be a way to mechanize this phase of production. Fern "cutters" must work


through the fernery selecting and cutting only mature fronds near the soil

surface. Soft, immature fronds that have not "hardened" have poor keeping

quality and are not desired by buyers. Twenty-five fronds are placed to-

gether in a bundle and tied with elastic bands or string after harvest.

Care after cutting is important to subsequent keeping quality. As

soon as possible after cutting and bunching fern should be placed with the

cut stem ends in water, preferably in a cooler. Most fern is harvested,

crated and shipped to market by refrigerated express the same day. Infor-

mation on storage of cut leatherleaf fern is not available at this time, but

holding fronds for short periods of up to one week at 420F. has been suc-


Leatherleaf fern is packaged 40 bunches to a box or crate lined with

newspaper or cushion-paper. Lining the shipping container is necessary to

prevent bruising damage to fern and to act as insulation to keep fern cool.


Leatherleaf fern is shipped throughout the United States and many

foreign markets by refrigerated trucks, ships and airplanes. Most markets

in the U.S. are located near large population centers.

Many growers ship fern directly to wholesale distributors, while others

sell through commission markets. Some growers also ship directly to retail

florists while another method of distribution and sale is through truck sales


Growers usually find their own buyers and obtain higher profits if

they sell on a pre-arranged price.

To simplify information in "Leatherleaf Fern Production in Florida" it is
sometimes necessary to use trade names of products$ equipment and firms. No
endorsement of named products is intended nor is criticism implied of simi-
lar products which are not mentioned.