The use of seedlings is a common method of establishing woody
species. Because of the increased demand for these seedlings, many species are
in chronic short supply. One alternative is to collect and directly plant seeds
of the desired plants instead of seedlings. Direct seeding has the potential to
reduce seeding establishment costs and may increase the quality of seedlings
that eventually develop. This information sheet has been prepared to aid in the
collection of quality woody plant seed and to minimize the risk to that seed
quality during handling, storage, transportation, and seeding.
Selecting Collection Sites
Seed should be obtained from seed sources developed from tree
improvement programs or from natural sources collected within 100 to 150 miles
of the seeding location. In selecting potential parent trees or stands,
consideration of the outward appearance, form or growth (phenotype) is
important. When the seed crop allows, collection should be from the best
possible healthy phenotypes and away from sources exhibiting disease and insect
problems. These issues are very critical when dealing with major timber species
such as walnut, pecan, Northern red oak, and white oak or when traits such as
heavy fruit production of specific plant color are desired. Trees and
plantations of unknown origin should be avoided for seed collection unless
knowledge of their attributes indicates otherwise. Collect species that are
growing in their typical habitat. Isolated trees or groves should be avoided
because of the possibility of non-viable seed resulting from poor pollination or
the possibility of excessive in-breeding.
Scouting for Seed Crops
Flowering is the first indicator of a potential seed crop.
Without flowers there will be no seed. Casual observations can appraise the
effects on potential seed production and also give an indication of how
widespread any detrimental effects might be on developing seed. In most species
fruit matures the same season that flowering occurs. A notable exception is the
red oak group, which takes two years for its seed to mature. With many species,
development of fruit set to fruit maturity is accompanied by a more or less
steady increase in fruit size, allowing progress to be monitored. However, oak
acorns show little size increase until mid-summer and are thus very difficult to
observe from the ground until well into the growing season.
As fruit maturity approaches, scouting should include sampling
seed/fruit from the potential parent trees for soundness. This can be done by
cutting or cracking a sample of seeds and inspecting for hollow, insect damaged
or otherwise abnormal seeds. By doing this, any trees with a high percentage of
unsound seed can be eliminated form the collection activities.
In general, the larger the seed crop, the higher the quality of
the seed. Thus, for species where the seed can be stored for long periods, it is
very desirable to take advantage of the periodic "bumper" seed crops. Species of
this type include pine, ash, sweetgum, dogwood, redbud, black locust, sumac,
holly, blackhaw, hackberry, redcedar and river birch. Other species such as oak,
hickory, walnut, butternut, hazelnut, and maple can not be stored for long
periods , making seed availability dependent on the annual seed crop.
Once scouting has revealed the potential
presence of a seed crop of sufficient quantity, a number of things should be
considered in planning the collection.
Several things can be done prior to seed maturity to greatly increase the
efficiency of collection activities. For species that are collected from the
ground, any cleaning of the area under the canopy of the trees will be helpful.
The removal of understory trees and brush, mowing of herbaceous plants, and
removing sticks and leaves by rake or blower will make the collection more
comfortable to perform and make the seed easier to find and pick up from the
The time period available for collection varies widely by
species and from season to season. For many species the collection period is a
function of how fast wildlife is consuming it rather than the development of the
seed itself. In other species seed dispersal occurs soon after fruit maturation,
narrowing the collection window considerably. For yet others, such as sycamore,
holly and hackberry, seed is retained on the tree until well into the winter,
allowing a long collection season.
Collecting before the seed is mature is the
quickest way to turn a good seed crop into a poor seed crop. However, some
species must be collected somewhat immature before seed dispersal (i.e. sweetgum)
or to lessen the amount lost to consumption by wildlife (i.e. hazelnut, paw
paw). Seed maturity can be checked by cutting the seed and inspecting the center
(endosperm). If the seed has a well-defined seed coat and the endosperm is
generally white, firm and fills the seed cavity, the seed is probably ready for
collection. In addition, visible changes in fruit color, especially for fleshy
fruits, can be used as a guide in determining fruit maturity.
Careful timing of acorn collections is
important. Frequently there is a heavy crop of acorns in early autumn consisting
of aborted, unsound acorns. The mature, sound acorns will not begin falling
until some 2 to 4 weeks later. Sample early acorn collections frequently for
maturity and soundness. Sound acorns will exhibit a bright white to orange
(depending on species), firm endosperm that fills the seed coat. Another good
indicator of the general quality of acorns is the cap scar. Sound, mature acorns
will be free of the cap or easily removed form the cap (except bur oak and
overcup oak) and the cap scar will be distinct and exhibit a bright, clean
How to collect:
Equipment for collection is open to imagination and ingenuity. Hand picking from
shrubs and small trees such as redcedar, hazelnut, dogwood and redbud is very
effective. Raking under nut trees, where good ground preparation has been done,
is helpful. If ground preparation was not accomplished ahead of time, rakes or
backpack blowers can be used to expose heavy seeds such as acorns, pecans and
walnuts for hand picking. Other alternatives include spreading cloths or nets
under species such as mulberry, redcedar, dogwood, and hackberry and flailing
the limbs to dislodge the fruit or collecting seed from downed logging slash and
Heating is the number one enemy of all
collected seed/fruit. If at all possible, plant immediately. If not, then
between collection and use, heating must be prevented. Place collected fruit in
canvas bags, extract the seed as soon as possible after collection and place in
cold storage until sown. Proper handling and storage is critical.
Play it safe! Safety is of paramount
importance and amateur collectors should be careful in collection activities.
Think about safety and vary the precautions you take to suit site conditions,
tree species and collection methods. Make sure that all equipment is in top
condition and properly serviced. It is advisable to work as a team, wear safety
goggles, appropriate clothes, safety hat and footwear; and take a first-aid kit.
Seeds can often be collected safely from the ground or by using a stepladder,
but if you plan to climb high trees, take extra care. For some people, tall
trees may be too difficult to collect seed from safely and should be left to
professional seed collectors.
Seed Handling and Storage
Handling and storage of seed need not be an overwhelming task.
Keep in mind that a seed is a living organism and the same situations that harm
other living things (too hot, too cold, too dry, lack of oxygen, rough handling,
etc.) will also harm the seed. For purposes of storage and handling,
seeds/fruits can essentially be divided into two groups: fleshy and non-fleshy.
Fleshy: Begin processing the fruit soon
after collection to avoid the damaging process of fermentation. Fleshy fruits
should first be soaked in water to soften the pulp. After soaking, the fleshy
material can be hand squeezed, mashed by a wooden block, rolling pin, or removed
with a fruit press. After maceration, the loosened seed must be separated from
the pulp. Screens or water flotation methods are effective. The pulp and empty
seeds will float and can be skimmed off. After separation, wet seed must be
If refrigeration is not available, fleshy fruits should be kept
spread in thin layers preferably on screens in a cool, well ventilated location.
If this is impractical, place them loosely
in open weave bags in a cool location with adequate space between the bags for
good air circulation. Inspect the bags frequently for signs of heating. If
heating occurs, spread the seed immediately, even if it has to be on a parking
lot or shop floor. Seeds can also be stored over winter by burying them 1-2 feet
underground, either in 4-6 mil polyethylene bags or loose. Black walnut should
be treated as fleshy fruit. The husk should be removed as soon as possible to
avoid overheating and seed damage. Hulled walnut seeds can be floated to
separate the filled seed from the unfilled. Most of the bad seed will float.
Seeds of many dry fruits must be separated from a pod or capsule. Extracted seed
should then be air dried. Spreading the seed in thin layers outdoors on canvas
or plastic sheeting is fast and economical. To prevent mold and loss of seed
viability, the drying area should be protected from the elements. Acorns can be
cleaned and separated satisfactorily by floating them in water (This will not
work with bur oak or overcup oak). Acorn caps should be removed prior to
floating. Skim off debris and empty floating seeds.
All seeds should be spread and allowed to
dry as soon as possible after collection. If transportation to the planting site
is not practical soon after surface drying, acorns should be bagged in
polyethylene bags of 4-6 mill thickness and placed in a cool location with
sufficient space between bags to allow free air movement. If at all possible
keep white oak species below 40 degrees Fahrenheit, but above freezing, to slow
germination. Excessive drying is as deadly to acorns, pecans, walnuts, and
hazelnuts as is overheating. As with fleshy seeds, if refrigeration is a
problem, non-fleshy seeds, can be stored over winter by burying them 1-2 feet
underground. Acorns form the white oak group can only be stored successfully for
2-3 months under most circumstances. Germination with this group is very
difficult to delay.
Hazelnuts require some special handling
also. Because of losses to wildlife, hazelnuts have to be collected while the
husks are still quite green. When collected green, they are subject to excessive
heating if not allowed to dry sufficiently. They should be spread thinly and
stirred frequently until the husks are cured. Place the dehusked seed in 4-6 mil
poly bags and keep cool with good air circulation. Silver maple should be
handled similar to hazelnut, but for a different reason. Silver maple has a thin
seed coat that allows moisture to escape relatively rapidly. However, if the
seed is not dried sufficiently before bagging, it will over heat in a matter of
hours, even in cold storage. The greatest danger of heating is past when the
seed coat has dried to a uniform light tan and the wing is slightly brittle.
Even then, the seed should never be packed tightly into a container.
This information note is adapted from
information on seed collection by William G. Yoder, retired, Missouri Department