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Group Title: Circular - University of Florida Institute of Food and Agricultural Sciences ; 414
Title: Seed propagation of woody ornamentals
CITATION PAGE IMAGE ZOOMABLE
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Permanent Link: http://ufdc.ufl.edu/UF00067174/00001
 Material Information
Title: Seed propagation of woody ornamentals
Series Title: Circular
Physical Description: 8 p. : ; 23 cm.
Language: English
Creator: Hamilton, David F
Midcap, James T
Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service
Place of Publication: Gainesville Fla
Publication Date: 197-
 Subjects
Subject: Plants, Ornamental -- Propagation   ( lcsh )
Plants, Ornamental -- Seeds   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: David F. Hamilton and James T. Midcap.
General Note: Caption title.
General Note: "4-6M-77"--p. 3 of cover.
Funding: Circular (Florida Cooperative Extension Service) ;
 Record Information
Bibliographic ID: UF00067174
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 20570225

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Full Text





HISTORIC NOTE


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

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




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SEED PROPAGATION OF WOODY ORNAMENTALS
David F. Hamilton and James T. Midcap*
For many years seed propagation was the principal method
of producing new plants of many woody ornamentals. It was the
least expensive means of propagation to produce a large number
of new plants from a minimum of stock material. Seed propaga-
tion is still used frequently to grow many plants which cannot
be propagated asexually. The main disadvantages of seed or
sexual propagation are failure to produce plants true to variety
and the longer time required to produce a salable plant.
When propagating woody ornamentals from seed, it is impor-
tant to collect fruit as soon as ripe and before seeds have been
dispersed. Seed of some plants will germinate readily if har-
vested immediately after fruit ripens, but if harvested after
seeds have dried on the tree, pretreatments may be necessary.

Signs of Maturity Vary
There are no set rules to determine when seeds of selected
species are mature and ready for collection. Changes in physical
appearance of fruits such as size, shape, weight and color can
serve as visual guides to seed maturation. As an example, fruits
of southern magnolia are a brilliant red when mature and fruits
of most junipers change to a deep blue at maturity.
Viable seeds of many ornamentals fail to germinate immedi-
ately when placed under conditions considered optimum for
germination. Such seeds are said to be dormant. However, dor-
mancy is relative because conditions restricting germination vary
widely by 'species. Dormancy is normally the result of the inter-
action of environmental conditions and hereditary properties of
plants. Under various conditions, either the hereditary properties
or environmental conditions can predominate and prevent germi-
nation.
Many woody ornamental plants grown in Florida produce seed
that exhibit no dormancy and will germinate readily as soon as
fruit are mature and harvested. However, viability of many seed
is often very short, sometimes only 3 to 10 days. This situation
is especially true for seed coming from pulpy or fleshy fruit.
Such seed should be planted immediately after harvest because
they lose their viability if stored.


* Extension Rural Development Specialist and Extension Woody Ornamentals Specialist,
respectively.









Handling Seed from Fleshy Fruits
Fleshy fruits include most palm species, southern magnolia,
ardisia, podocarpus, ochrosia, sea grape and carissa. When stor-
age cannot be avoided, seeds should be separated from pulp as
soon after collection as possible to avoid damaging fermentation.
Seeds of species with thin flesh, such as magnolia, can be air-
dried and planted with seed coats intact. After an initial cleaning
or washing such fruits should be spread out in thin layers and
dried in the sun or a warm room. An occasional stirring is helpful.
Flesh from fruits of palms, sea grape and carissa can be re-
moved by hand or by any of several macerating machines. Resi-
due and seeds may then be separated effectively by flotation in
water. Empty or nonviable seed, pulp and other debris will either
float or sink more slowly than sound, viable seeds. This can be
accomplished by putting macerated material in a slightly tilted
container. Direct a stream of water from a hose at an angle to
create a rotary swirl and lifting effect. Debris will float to the
surface and spill over the edge of the container as the water
overflows. Slight stirring of material in the bottom of the con-
tainer is required.
Similar floation methods are used to separate poor from good
seeds that have no flesh such as oaks (Quercus spp.)
After separation, wet seeds should be surface dried or fully
dried in the sun or indoors if it is to be stored. A sieve can be
used for final cleaning to screen or blow away remaining debris.
Seeds from dry fruits such as redbud, pines and junipers re-
quire only cleaning before planting or storage. Cleaning is simply
separation of dry seeds from pods, capsules, or cones, and re-
moval of wings and other appendages.
Whether seed are planted immediately after harvest or stored,
they should not be treated harshly because they are live plant
material. Handle bags or containers of fruits and seeds gently
and avoid rough cleaning procedures. Leave seed to dry in
heated air only the minimum length of time. Use the lowest pos-
sible air temperature to accomplish this job because excessive
heat can injure seeds and reduce viability.


Factors Influencing Storage
Many factors influence longevity of seed in storage including
type of seed, stage of maturity, viability and moisture content
when stored and air temperature. However, a few generaliza-
tions can be made about storage.








(1) Fully-ripened seeds remain viable longer than seeds col-
lected when immature.
(2) Seeds with hard impermeable seed coats store better than
those with fleshy coverings.
(3) Fluctuations in temperature and moisture are less favor-
able than constant conditions.
Recommended storage temperature and moisture requirements
vary for seeds of woody ornamentals. A rule of thumb applied
to agricultural seeds states that conditions for long-term storage
are good if the sum of degrees F and percent of relative humid-
ity equals 100 or less. This should serve as a rule for storing tree
and shrub seeds.
At the National Seed Storage Laboratory, seeds of many differ-
ent plants are stored in airtight containers at 400F or 5'C.
and 32 percent relative humidity. Oak (Quercus) seeds have re-
mained viable for 21/2 years stored in polyethlylene bags at 50C.
Seeds can be stored satisfactorily in metal cans, plastic bags, and
paper or aluminum-foil lined envelopes.
A few plants grown from seed by nurserymen in Florida are
dormant because of a hard seed coat. Seed coats may be imper-
meable to water, air or both. Seeds which have hard and imper-
meable seed coats include Jerusalem-thorn (Parkinsonia acu-
leata), redbud (Cercis canadensis), sweet acacia (Acacia far-
nesiana), Poinciana, spp. and other legumes. The usual method
of overcoming this is by mechanical or acid scarification and
soaking in hot water. Scarification is any process to break,
scratch or alter the seed coat and make it permeable to water
and air.


MECHANICAL SCARIFICATION
Mechanical scarification is accomplished by tumbling seeds in
containers lined with sandpaper or other abrasive materials or
seeds can be mixed with coarse sand or gravel in a revolving con-
tainer. Small lots of seed can be scarified by rolling them on a
cement floor using a brick or board.
To determine if seeds are properly scarified, a test lot can be
germinated. The seeds may be soaked to observe swelling or the
seed coats may be examined with a hand lens. Seed coats gen-
erally should be dull but not deeply pitted or cracked enough to
expose the inner parts of the seed. Scarified seed will not store
as well as comparable nonscarified seed and should be germi-
nated as soon as possible.








Chief advantages of mechanical scarification are as follows:
1. It requires no temperature controls.
2. It involves no safety hazards to workmen.
3. Seeds remain dry and can be planted immediately.
Disadvantages are as follows:
1. Special equipment may be necessary.
2. Seeds must be free of pulp flesh.
3. Damage from overtreatment is extremely possible.
4. Seeds mechanically scarified do not store as well as those
scarified with acid or water.

SOAKING SEEDS IN WATER
Soaking seeds in water may overcome seed coat dormancy and
stimulate germination in some cases. Impermeable seed coats can
be softened by dropping seeds into 4 to 5 times their volume of
hot water (80-1000C or 190-2100F). Heat should be removed
immediately and seeds allowed to soak in the gradually cooling
water for 12 to 24 hours. Unswollen seeds can be retreated or
subjected to some other method of treatment. Seeds should be
planted immediately after the hot water treatment. Boiling seeds
or over-exposure to high temperatures is likely to result in in-
jury.

ACID SCARIFICATION
One of the most common methods of pretreating seeds with
hard and impermeable seed coats is to soak them in concentrated
sulfuric acid. This treatment is highly effective with many
species.
Special materials and equipment required include: (1) con-
centrated sulfuric acid to cover the seeds, commercial grade-95
percent pure; (2) acid-resistant containers of thick plastic or
glass are preferred; (3) wire containers and screens for
handling, draining and washing the seeds; (4) a supply of run-
ning water; (5) a safe place to drain away the dilute acid after
rinsing the seeds; and (6) facilities for drying the seed if they
are to be stored.

Steps in Acid Treatment
Steps in acid treatment are as follows:
1. Allow seeds to come to air or room temperature, especially
if they have been in cold storage.
2. Thoroughly mix seeds to be treated as one lot.








3. Determine the optimum period for immersion in the acid.
Time of treatment may vary from as little as 10 minutes for
some species to as much as 6 hours for other species. Time
can be determined on small lots of seeds in preliminary
tests by removing samples at set intervals and visually
checking thickness of seed coats. When coats become paper
thin, treatment should be terminated immediately.
4. Immerse dry seeds in acid for the required period, making
sure that all are covered. Usually one part seed to two parts
of acid will be adequate. Seed should be GENTLY stirred
during the immersion period. Treatment should be carried
out at 18-270C or 65-800F. If temperatures are lower the
seeds must be soaked longer; if higher they must be soaked
less time.
5. Remove seeds from the acid and wash promptly and thor-
oughly over a wire screen in cool, running water for 5 to 10
minutes to remove acid residue. Apply plenty of water at
the start and stir carefully during rinsing.
6. Seed can be planted immediately while wet.

Precautions to Follow in Using Acid
PRECAUTIONS to take in use of acid are as follows:
1. Concentrated sulfuric acid is very caustic to skin and to
clothing and should be handled with great care.
2. Never pour water into concentrated sulfuric acid. It will
react violently by heating, boiling and splattering.
Several advantages of the acid treatment over mechanical
scarification are:
1. It is effective for many species.
2. It requires little special equipment.
3. Cost is reasonable. Acid can be reused.
There are also disadvantages. They are:
1. Length of treatment must be carefully determined.
2. Temperature must be controlled.
3. Workmen face a safety hazard.

COLD STRATIFICATION
Seeds of many other species of woody ornamentals such as
holly (Ilex spp.), southern magnolia (Magnolia grandiflora),
nandina (Nandina domestica, and sweet gum (Liquidambar
styraciflua) have embryos or endosperms that are nonfunctional,
or contain inhibitors at the time of seed maturity, and require a








period of cold stratification. Cold stratification is the subjection
of moist seeds to low temperatures for a specified length of time
before germination.
Steps in cold stratification are:
1. Soak seeds overnight or from 12 to 24 hours in water at
room temperature immediately prior to stratification.
2. Moist seeds are then mixed with the moistened but sterile
medium. Suitable media include well-washed sand, peat
moss, shredded sphagnum and vermiculite. The medium
must retain moisture. Seed should be mixed with 1 to 3 times
their volume of the medium or placed in layers 1/ to 3
inches thick alternating with equally thick layers of the
stratification medium. Layers of cheesecloth may be used to
separate the seeds and the medium. This eliminates the need
for cleaning resulting from mixing of the seed and medium.
Suitable containers for stratification are flats, trays,
boxes or cans which provide aeration, prevent drying and
allow drainage. Polyethylene bags no more than 0.004
inch thick have also been used successfully.
During stratification seeds should be examined periodi-
cally; if dry, the medium should be remoistened.
3. Place seeds in refrigerated storage. The recommended tem-
perature is between 3-50C or 37-400F. For most species of
seeds, the required period of low temperature is 3-4 months,
but some species such as southern magnolia may require
5-6 months.
4. Seeds should be planted immediately after removal from
refrigeration or they may return to a dormant state, and
require additional low temperature as well as losing viabil-
ity.

COMBINATIONS OF PREGERMINATION TREATMENTS
The purpose of combining two or more treatments is to over-
come double dormancy which may result from a combination of
hard seed coats, immature embryos or other factors. The com-
bination of scarification with cold stratification is effective for
many of these seeds. Also, a combination of warm and cold
stratification is another suitable treatment.
The procedure to prepare seeds for warm stratification is es-
sentially the same as for cold stratification. Planting seeds di-
rectly in a greenhouse for the desired time will suffice for the
warm period. Periods of cold temperature must follow the warm
temperature.









ENVIRONMENT FOR GERMINATION
Mediums used for germinating seed must have a high water-
holding capacity, good drainage and good aeration. A mixture
of peat moss and builder's sand in a 1:1 volume is used by many
Florida nurserymen. Various other materials such as shredded
sphagnum moss, vermiculite and perlite have also been used
successfully in germination mixtures.
Regardless of the media that is used for germination, it should
be sterile to prevent loss of seedlings by disease. A common di-
sease problem with seedlings is damping-off, which eventually
can cause death of the new plant. Damping-off is caused by cer-
tain fungi, primarily species of Pythium and Rhizoctonia. Con-
trol involves three separate procedures: (a) elimination of the
organisms during propagation; (b) control of environmental
conditions during propagation; and (c) keeping the propagation
area sanitized at all times. Excellent control can be obtained by
using sterile media, treating seeds and following good sanitation
practices. Five percent solutions of commercial bleaching prepar-
ations have been used satisfactorily to treat seeds.

Structures for Planting
Seeds may be planted in flats, pots, greenhouse benches and
similar structures. It is desirable to cover germination facilities
with moisture proof plastic, glass or other material to prevent
water loss from the medium and surrounding air. Plastic cov-
erings are most desirable because they maintain high humidity
without restricting movement of air or oxygen.
Optimum temperatures for germination of seeds of woody
ornamentals grown in Florida is 24-350C, or 75-950F. Variation
of 50C between night and day temperatures often stimulates
germination of many species, compared to a constant tempera-
ture. The lower temperature should be given during the dark
period.
Another critical problem in seed germination is depth of plant-
ing. Generally, seed should not be planted deeper than 1 to 2
times their diameter. Very fine or small seeds should be scattered
over the surface of the medium or planted thickly in rows. For
small seed this means dusting them onto the medium surface
without covering, or covering with a very thin layer of shredded
sphagnum moss. Larger seed should be planted less than their
diameter in depth since 2 to 3 inch planting depth is the maxi-
mum for any species. Seeds such as the coconut are an exception.









Importance of Moisture
The medium should be moistened prior to sowing of seeds.
After seeds are sown, the medium should be watered with a fine
mist or, particularly with small seeds, subirrigated. Both medium
and air surrounding the germinating seed must remain moist
throughout the germination process.
Germinating seedlings should receive adequate light to produce
short, stocky plants rather than weak and spindly ones. However,
full sunlight during very early germination should be avoided
with some seedlings because of possible injury from high tem-
peratures.
Seedlings should be transplanted into larger containers as
soon as the first 2 to 4 true leaves appear (not the cotyledonary
leaves). During transplanting, it is desirable to retain as much
of the medium around the roots as possible.

PROPAGATION OF PALMS BY SEED
Follow these eight steps in propagation of palms by seed:
1. Plant palm seed as soon as ripe. Seed of some species are
relatively short-lived and begin to lose viability in 2 to 3
weeks or less.
2. Remove fleshy coat, dry in the shade for a few days before
storage or plant immediately. Seeds that have been previ-
ously dried should be soaked in water for 2 to 3 days before
planting.
3. Before storage, dust seeds with a fungicide, such as fer-
bam, ziram or chloranil (Spergon).
4. To hasten germination, scarify or cut through the thick or
hard coat of the seeds.
5. Plant the seed in sterilized media in flats or beds. Mixtures
of peat and sand 1:1 by volume or peat, sand, and vermicu-
lite 1:1:1 by volume have proven satisfactory.
6. Keep seed bed moist and at a temperature of more than
5C until germination. Germination is considerably better
at high temperatures, 30-350C or 85-950F. Heating cables
may be used to raise temperature of seedbed.
7. Germination time of palm seeds varies with species. Chry-
salidocarpus lutescens and Phoenix roebelenii germinate in
about one month, whereas Chamaedora spp. require about
seven months.
8. Seedlings should be transplanted as soon as leaves are well-
developed to reduce root injury in transplanting.




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