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AGROFORESTRY TREE SEED PRODUCTION
Production Guidelines for Seed Orchards
Compiled by Patient. D Dhliwayo
Ester Bhebhe
ICRAF-Zimbabwe 2005
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1.0
INTRODUCTION
Community-based forestry and agroforestry programs around the world reforest denuded lands,
protect valuable watersheds and produce indispensable tree products for soil improvement and
fodder. These programs begin planting operations with a commodity of small size but great
importance-seed! Adequate supplies of high quality seed are necessary to grow high quality
seedlings. Unfortunately, shortages of seeds are common and limit the success of many
community-based tree planting programs. Any discussion about tree seed production must
consider the saying “garbage in garbage out”. If you plant junk seeds you will inevitably harvest
junk trees.
1.1
Local Seed Production
Organisations and individual farmers can overcome the “seed problem” by “growing their own
seed. Seed production serves organization and individuals in several ways;
1. Less time is spent searching for seed sources and less money is spent on seed
purchases. The time and money saved can be allocated to other activities.
2. Locally produced seed has a proven genetic quality for local environmental conditions.
3. Organisations and farmers also realize a financial benefit when seed is sold. Seed sales
increase income and decrease economic risk by diversifying farm production and
targeting new markets.
The International Centre for Research in Agroforestry (ICRAF) in Zimbabwe has operated
agroforestry projects since 1991. To meet the seed needs of their extensive planting programs,
ICRAF and its collaborators produce and distribute seed of 9 tree crop species. Seed production
focuses on multipurpose species with strong demands. All the 9 species are nitrogen fixing
leguminous trees, which produce large quantities of leafy biomass. They are commonly used to
produce fodder, green manure or mulch.
2.0
Meeting long-term seed needs
2.1
Seed Orchards
Relatively few organizations are willing or able to make the long-term commitment necessary to
establish orchards for the tree seed production. If the decision is made to establish seed orchards
a long term plan is very important. Several years of planning are required before the first tree is
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planted. A number of issues must be considered before establishment. Some relevant issues
include

Are there sufficient financial resources and have land tenure issues been resolved?

What type of orchard is appropriate for the tree species of interest?

Are there locations where tree species will flower early and heavily

Does the organization have the expertise to manage the seed orchard successfully
A seed orchard is an area where seeds of particularly valuable genotypes are produced to obtain
seed as quickly and economically as possible. This is a specialized plantation of selected species,
which are isolated to avoid contamination, and managed to produce frequent, abundant, and
easily harvested seed crops. Orchards can be used for genetic improvement and production of
large quantities of seed for operational planting. Generally, the benefits of orchards are the
production of seed with improved disease and insect resistance growth wood qualities,
adaptability and tree from.
2.2
Seedling seed Orchards
Seedling seed orchards are plantations with known family identity that are managed for
maximum seed production. They consist of a population of open (naturally) pollinated families of
selected trees. Often they are “first-generation” orchards that are the result of species and
provenance trials. Typically they result from rouging, a process of removing the trees with less
desirable genetic potential. Most multi-purpose tree seed orchards are of this type.
2.2.1 Site Selection Criteria
An ideal site will have;

good soil structure, drainage and fertility, with protection from high winds.

Seed orchards also require level or gently sloping terrain with easy access and good
security.

They should be located near the nursery or farm offices so that equipment and
personnel are readily available. This will aid in overall orchard efficiency by reducing
travel time to the site.
Generally, abandoned agricultural lands make good sites. It is important that site environment
characteristics encourage early and heavy flower production. Site requirements differ depending
on the tree species of interest.
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Seed orchards size depends on seed production objectives. Generally, if average rate of seed
production per tree is known, then calculating the number of trees needed to reach the
production per tree is known, then calculating the number of trees needed to reach the
production objective is straightforward. An orchard where insects are controlled and soil fertility
is well managed will yield seed of higher quality and quantity than an unmanaged orchard.
3.0
Orchard Establishment and Management
3.1
Land Preparation

Ripping to eliminate soil compaction should be considered on abandoned agricultural
land.

Soil pH should always be tested and nutrient levels amended as required to promote
growth and flowering.

Generally the elements of importance are nitrogen for growth and phosphorous for
flowering. However, a deficiency of any macro or micronutrient can effect seed
production.
3.2
Planting

Orchards should be established with planting material of high quality.

Containerized seedlings have worked well in most tropical conditions.

Weed control is very important and can be achieved through chemical, mechanical or
manual means.

Planting seedlings of high quality and reducing weed competition are the first steps to
developing a successful orchard.

Tree spacing in a seed orchard is wider than timber plantations. Actual spacing will be
determined by the canopy shape and size of each specific species. Often seedling s a re
planted at closer spacing. After a few years inferior tree are removed to achieve the
desired spacing.
3.3
Cultural practices
3.3.1 Irrigation
Irrigation will improve establishment success and help maintain growth and vigor of the seed
orchard. On arid sites it may be possible to induce flowering by timing of irrigation. There is
some indication that flower induction is promoted by moisture stress in some tree species.
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3.3.2 Ground covers
Ground covers should be considered between rows to suppress weeds and conserve
moisture. The orchard floor will be protected from wind and water erosion while soil nutrients
and soil moisture will be retained for longer periods.
3.3.3 Pruning
The size of the canopy of the tree will influence flowering and seed production. Generally,
the larger the canopy the greater the seed production. Pruning and coppicing can be used to
modify tree form to increase sunlight penetration and canopy size. Both modifications
enhance flowering, seed production and ease of seed harvest.
Each tree species responds to pruning differently, so prune with care until the tree responses
as desired. Pruning and coppicing must be timed to disrupt seed production as little as
possible
Most tropical legumes will benefit from management to increase seed production. A word of
caution, poor timing or lack of care in applying these practices will affect seed production and
may take a season or more for the trees to recover and produce the next seed crop.
3.3.4 Pests and Diseases
A major factor to determine whether a seed orchard is economically viable will depend upon
success of controlling orchard pests. There a re 2 categories of consequential orchard pests,
those that attack the flowers and seeds and those that attack the tree. Monitoring and
control measures are important strategies for improving seed yields.
3.3.5 Record keeping
Record keeping will provide a reference of orchard performance and give insight into productivity
and corrective actions that should be taken if problems develop.
Records of importance include

Age at first flowering

Months of flower production and level of flowering

Complete weather records and historical data will aid in seed orchard management and
help in planning future orchards.

Recording fertilizer rates and formulations as well as dates of application are important
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
Irrigation quantity, frequency, and dates will help to establish relationships between
flowering and seed production

Insect and disease management records of material used, dates and rats applied,
method of application and results are also very important.

Silvicultural treatments such as pruning and thinning should be recorded.

Site maps should be updated when trees are removed.

Records of adverse environmental conditions such as droughts, high winds, floods and
heavy rains and hurricanes should be noted and the effect these events had on flowering
and seed production
4.0
. Techniques of Seed Harvesting and Handling
When the seed of most tree legumes is mature and ready to harvest, pods will become dry and
change colour. This indicates that the seed embryo is mature ands can be harvested without loss
of germination ability. Harvest windows are fairly narrow about 2 to 4 weeks in duration. It is
important to stay on top of harvesting. Late harvesting can result in yield loss due to pod shatter
and pest predation, so correct harvest timing is essential.
Dry seed pods are usually collected by hand picking Extraction of seeds can be accomplished by
beating the pods with a flail, walking over them, or rubbing them through a screen. For larger
operations, commercial threshers are more practical.
Cleaning infested or bad seed using floatation will work with seed having hard seedcoats i.e.
Leucaena. Fill a container to about 25% with seed and pour in clean water until the container is
75% full. Good seeds will sink. The poor seeds, trash, and insects will float to the top where they
are removed. Stir the water and continue to skim off the trash. Slowly pour off the water by
tilting the container at a slight angle. The water treatment may need to be repeated several
times to remove the bulk of poor seeds. Seeds are removed from the container and spread out
on a drying rack until dry then stored. Air sorting is another method that can be used to blow off
chaff and empty seeds.
Proper storage is necessary to maintain seed viability. Most seeds with hard seedcoats store for
1-2 years with little loss of viability. The factors that will affect seed viability are;

moisture content of the seed

humidity
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
temperature
For long term storage a moisture content of 4 to 6% is ideal. Storage should be about 4.510degree C with relative humidity no higher than 70 but preferably below 50. Seed sorted for
extended periods should be sealed in airtight moisture resistant containers. This will protect seed
against insects disease and mould.
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5.0
FACTSHEET06 – NURSERY MANAGEMENT
(This factsheet was adapted from “Agroforestry for the Pacific Technologies” Number 12, July
1995 by James M. Roshetko
At a glance:
Species: Appropriate seed treatment
Acacia angustissima: A, C
Acacia crassicarpa: B
Cajaus cajan: A, Nil
Calliandra calothrysus: A, B, C
Gliricidia sepium: A, C, Nil
Leucaena spp: B
Sesbania sesban: A, B, C
Introduction
Seeds of some plants may not germinate immediately after being planted. All seeds have an
outer layer that protects the delicate embryo inside. With species that do not germinate
immediately, this covering or seed coat may be waxy or hard preventing the water that is
necessary for germination to enter the seed. Under natural conditions, the seed coats break
down over time (sometimes years). Once the breakdown is complete and if the seed embryo has
not been damaged, germination takes place under favourable conditions.
Seed treatment has a number of advantages:

Because of the breaking of the physical barrier that inhibits the uptake of water, seed
treatment allows quicker emergence of the seedling

Under natural conditions, the seed coats break down slowly over time resulting in the uneven
germination of a seed crop from the same year. Seed treatment allows seeds to germinate
within a few days of each other giving rise to a uniform crop of seedlings.
There are several types of seed treatment. These include soaking in cool water, immersing in
hot water, treating seed with acid and physical weakening of the seed coat e.g. scrapping off
portions of the seed coat.
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A. Cool Water Treatment
Soak seeds in cool, water at room temperature until the seeds swell. The volume of water
should be about five times the volume of seeds. Soaking time may vary from 6 to 48 hours
depending on species, age and quality of seed. This treatment is appropriate for seeds with a
thin or soft seed coat, recently harvested seed, seed of small size and large quantities of seed
B. Hot Water Treatment
Pour boiling water over the seeds at a volume five times the volume of seeds. The seeds must
be stirred gently during the 2 to 5 minute soak. Pour off the hot water, replace with cool water
and soak for 12 hours. This treatment is appropriate for seeds with hard or thick seed coats, old
seed and large quantities of seed
C. Physical Weakening of Seed Coat
Cut or scrape a small opening in the seed coat. A knife, nail clipper, metal file, sand paper or
sanding block can be used for this operation. To avoid damaging the seed embryo, cut or scrape
the seed coat only opposite the point where the seed was attached to the fruit of the mother
plant. Seed treated in this way is soaked for 12 hours in cool water. This treatment is
appropriate for all types of seed with the exception of those that are very small or having a soft
seed coat. However, being time consuming, this treatment is feasible only for small quantities of
seed.
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6.0
FACTSHEET01 – Calliandra calothyrsus
At a glance:
Altitude
250 - 1800 m
Mean annual temperature
22 - 28 0C
Mean annual rainfall
700 - 4000 mm
Soil type
Light textured, slightly acidic soils. Does not tolerate waterlogging
Main uses
Fodder, bee forage, aesthetics
Introduction
Calliandra is native to humid and sub-humid Central America. The tree grows best between 250
and 800 m altitude in areas with 2000 to 4000 mm rainfall and a 3 to 6 month dry period.
Calliandra grows well on light textured, slightly acidic soils.
Propagation and Management
Calliandra is easily propagated by seed. There are an average of about 20 000 seeds per kg.
Potted seedlings produce best results. Seed is pretreated by soaking for 12 to 24 hours in cold
water. Seeds can be sown in beds of sand in rows spaced 10 cm apart. In the row the seeds
are sown thickly but only covered as deep as the size of the seed by soil. Beds need to be
watered about twice a day depending on weather conditions. A shade of grass or other suitable
material needs to be provided above the beds to conserve moisture. Most seed germination
occurs between 10 and 25 days.
Because seedlings grow quickly in the field, no special plantation management is needed except
weeding in the first year. For fodder production, spacing can be as dense as 0.5 m x 0.5 m to
0.75 m x 0.75 m. Where the tree is intercropped with other forages, inter-row spacing can be
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increased to 1.5 m to 2.0 m. Firewood can be obtained as a by-product of the fodder banks.
Highest yields of fodder are obtained from coppicing when the shrubs are cut at 0.75 m to 1 m.
Functional uses
Fodder for ruminants – leaves and fresh pods are an excellent supplement to protein. The
leaves contain up to 25% crude protein. However, there are some compounds in the browse
called tannins. These can result in reduced digestibility of the fodder in some provenances.
Bee forage – flowers contain nectar and may last throughout the year under favourable
conditions.
Nitrogen fixing – Calliandra is able to fix atmospheric nitrogen through symbiotic interaction
with rhizobia.
Soil improvement – high leaf biomass production and high yields of protein-rich leaf material
make it very suitable as a green manure
Firewood – the tree is multistemmed and grows fast giving fast-burning wood.
Erosion control – the shrub can be used to recover land exhausted by agriculture
Ornamental, shade & shelter – Calliandra’s beautiful red ‘powder puff’ flowers make it an
attractive ornamental. The dense foliage provides shade and shelter around the home.
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7.0
FACTSHEET02 – Cajanus cajan
At a glance:
Altitude
Sea level - 2000 m
Mean annual temperature
18-38 0C
Mean annual rainfall
400-2500 mm
Soil type
Prefers alluvials, vertisols and alfisols. pH 5 to 7. Sensitive to saline soils and susceptible to
waterlogging.
Main uses
Fodder, soil improvement, food.
Introduction
Pigeonpea is native to India. The species is now grown all over the tropics but especially in the
Indian sub-continent and East Africa. The shrub grows best in savannah habitats in tropical and
sub-tropical, frost-free zones with optimum annual rainfall of 600-1000 mm.
Propagation and Management
Pigeonpea is best established by direct seeding in a well-prepared field. There are up to 14 000
seeds per kg. The seed rate is 8 kg per hectare. Seed pretreatment is not necessary. Seed
germination and emergence is usually complete 2 to 3 weeks after sowing.
Weeds must be controlled as the shrub exhibits slow and weak initial growth in many instances.
When grown for nitrogen fixing and general soil improvement, the crop is grown as a sole crop at
a spacing of 1 m by 1 m. Pigeonpea is commonly grown as an intercrop with maize, sorghum
and millets, cassava, sunflower, soyabean and other food crops. Pigeonpea fits very well with
these crops because it requires very little resources, especially in its early stages of growth.
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Uses
Food – the fresh pods can be used as a vegetable. Fresh pods contain vitamins, especially
provitamin A and vitamin B complex. The seeds contain 7-10% water, 14-30% protein, 1-9%
fat, 36-65% carbohydrates, 5-9% fibre and 4% ash. The beans are cooked and known as dhal.
Fodder – pigeonpea can be fed to livestock.
Firewood – the tree is multi-stemmed and grows fast providing wood that is of low calorific value
and burns fast.
Nitrogen fixing – It has been shown in Northern India that long-duration pigeonpea can fix up
to 200 kg N/ha over a 40-week period.
Beekeeping – honey bees collect nectar from the flowers.
Soil improvement – the root system is reported to break plough pans, thus improving soil
structure, encouraging infiltration and minimizing sedimentation. Leaf fall adds to the organic
matter of the soil and provides additional nitrogen. High leaf biomass production and high yields
of protein leaf material makes it very suitable as a green manure.
Intercropping – due to its hardiness, ability to grow on residual moisture and slow early growth,
pigeon pea is an ideal, non-competitive crop to plant with cereals.
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FACTSHEET03 – Sesbania sesban
At a glance:
Altitude
100 - 2300 m
Mean annual temperature
18-23 0C
Mean annual rainfall
500-2000 mm
Soil type
Tolerates seasonal or permanently waterlogged soils as well as saline and acidic and alkaline
soils.
Main uses
Soil improvement
Introduction
The origin of Sesbania sesban is unclear but it is widely distributed and cultivated throughout
tropical Africa and Asia. Africa is its centre of diversity. Sesbania sesban fixes nitrogen. The
shrub grows well in the subtropics and can withstand some waterlogging. Sesbania is common
along streams and dambos. Even though the shrub is more common where there is a high water
table, it exhibits some tolerance to moisture stress.
Propagation and Management
Sesbania seed is protected by a hard seed coat. Seed treatment to weaken this coat helps to
ensure rapid and uniform germination. Seed can be treated using hot and/or cold water. The
seeds can be dipped for 2 to 5 minutes in hot water, which has been taken off the heat source.
The volume of the water is five times that of seed. Seeds can also be soaked in cold water for
12 to 24 hours. Seeds germinate in about 14 days. Sesbania needs rhizobia for good growth.
Seeds can be innoculated by using soil from old Sesbania stands in the seedbed or pots. There
are between 85 000 and 100 000 seeds per kg. In improved fallow systems, the shrub is planted
at a spacing of 1 m by 1 m using nursery-raised seedlings. Potted seedlings produce the best
results, as there is minimal root disturbance at planting. Bare roots also give good results these
are seedlings that are pulled up from the nursery with no soil on the roots and planted directly
into the field. In the improved fallow technology, the shrub is left to grow for at least two years.
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After this period, the shrub is cut at ground level and a food crop such as maize planted. The
food crop will benefit from the nitrogen fixed by the preceding Sesbania as well as from improved
soil structure and texture.
Uses
Fodders for ruminants – leaves are an excellent supplement to protein. The leaves contain up
to 25% crude protein.
Medicinal – it has been reported that the fresh roots and leaves are used to treat scorpion
stings, boils and abscesses. Sesbania is also said to treat sore throats, gonorrhea, syphilis,
spasmodic fits in children and jaundice during pregnancy.
Nitrogen fixing – Sesbania sesban will increase soil nitrogen through symbiotic interaction with
rhizobia. The shrub improves soil fertility in short-term rotation fallows.
Soil improvement – the root system breaks plough pans, thus improving soil structure,
encouraging infiltration, minimizing sedimentation and smothering weeds. Leaf fall adds to the
organic matter of the soil and provides additional nitrogen. The shrub is useful in combating the
parasitic weed, Striga assiatica.
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FACTSHEET04 – Leucaena spp
At a glance:
Altitude
30-1500 m
Mean annual temperature
18-30 0C
Mean annual rainfall
600-3500 mm
Soil type
Prefers slightly acid, fertile soils but is tolerant of leached soils
Main uses
Fodder, soil improvement
Introduction
Leucaena diversifolia is of Central American origin. The naturalized distribution of the species
includes the Caribbean, Africa and Southeast Asia. L. diversifolia grows naturally in moist,
evergreen environments. It is tolerant to cool climates but not frost. This species does not
tolerate drought very well having originated in areas of high rainfall and short dry seasons.
Propagation and Management
Seeds of L. diversifolia are very small. There are 60 000 to 80 000 seeds per kg. Seeds have a
hard, water resistant coat which needs to be weakened for good germination results. Weakening
of the seed coat–-scarifying–-can be done by scratching the surface or by hot water treatment.
The seeds can be soaked for 3 to 5 minutes in boiling water that has been set aside from the
heat source. Seedlings emerge after 7 to 10 days.
The seedlings can be transplanted directly into the field 8 to 12 weeks later. Potted seedlings
produce the best results but during the rainy season, bare roots can also be used. For
establishing fodder banks, the trees are planted at a spacing of 1 m by 0.5 m. The inter-row
space can be increased to 2 m where intercropping with other grass fodders, such as banna
grass, is practised. The shrubs are cut up to 3 times a year at an average height of 60 cm above
the ground. The small soft twigs and leaves can be fed fresh to animals or dried.
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Uses
Fodder for ruminants – fodder from L. diversifolia has lower palatability and digestibility and
higher tannin levels than L. leucocephala. Fodder quality is intermediate compared to other
Leucaena species. In Zimbabwe, L. esculenta, L. leucocephala and L. pallida are the top three
species in terms of fodder.
Firewood – the tree grows fast and the main stems provide wood of fast burning quality.
Nitrogen fixing – roots are able to fix atmospheric nitrogen because of the symbiosis with
Rhizobia and root fungi thereby enhancing soil fertility.
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Factsheet05 – Acacia angustissima
At a glance:
Altitude
30 - 2600 m
Mean annual temperature
5 – 30 0C
Main uses
Fodder, soil improvement
Mean annual rainfall
600 - 2800 mm
Soil type
Prefers free-draining soils and tolerates acid soils.
Introduction
Acacia angustissima is thought to have originated in Belize, Central America. In its natural
environment, the tree grows on hillsides, rock slopes and in grasslands. A. angustissima grows best in
higher elevation and may fail to flower at very low elevations. The tree is able to withstand up to 8
months of no rain.
Propagation and Management
Seeds of A. angustissima are very small. There are 90 000 to 100 000 seeds per kg. The seeds have
a hard, water-resistant coat that needs to be weakened for good germination. Weakening of the seed
coat can be done by scarifying or by hot or cold water treatment. Soaking seeds in cool water
overnight produces the best results. Seeds can be sown in beds of sand in rows spaced 10 cm apart.
Within the row, the seeds are sown thickly but covered as deep as the size of the seed by soil. Beds
need to be watered about twice a day but the frequency will depend on the weather. A shade of grass
or other suitable material needs to be provided above the seedbeds to conserve moisture.
Seedlings emerge after 7 to 10 days and these can be transplanted directly into the field 8 to 12
weeks later. Potted seedlings produce the best results. For establishing fodder banks, trees are
planted at a spacing of 1 m by 0.5 m as pure stands. The inter row spacing can be increased to 2 m
where intercropping with grass fodder species such as bana or napier. The shrubs are cut up to 3
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times a year at a height of 50 cm to 1 m above ground level. The cut material can be fed fresh to
ruminants or can be dried and stored for later use.
Uses
Fodder for ruminants – leaves and fresh pods are an excellent protein supplement. The leaves
contain up to 30% crude protein. There are some compounds in the browse called tannins.
These cause reduced digestibility of the fodder in some provenances
Firewood – the tree is generally single-stemmed until cut. Once cut, the tree becomes multistemmed and grows fast giving fast-burning wood.
Nitrogen fixing – A. angustissima is able to fix atmospheric nitrogen through symbiotic
interaction with rhizobia.
Soil improvement – high leaf biomass production and high yields of protein-rich leaf material
make it very suitable as a green manure.
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