How To Collect and Store Native Plant Seeds
Excerpted from: How to Collect and Store Seeds
Most native plants are collected by hand. This is because desired species don’t typically grow in
large, pure stands, and the topography of their environments often limits using mechanical equipment.
Plants are easiest to identify when they are flowering, so it is a good idea to mark individual plants
with flagging tape or to write down specific landmarks to help you relocate populations when the
seeds are ready.
Always get permission from the landowner when collecting on private land, and never collect on
public land. Areas destined to be developed or destroyed in the near future provide excellent sites
for collecting seeds, provided the landowner has given permission.
Take at most only ⅒ of the seeds so that enough seeds are left to reseed and perpetuate
the stand.
Never collect seeds from rare or endangered species — collect only from plants that you find
growing abundantly in a given area to ensure that you do not eradicate an isolated population.
The tools and material you will need depends on the size of the harvest. Basic equipment includes
gloves, boots, drop cloths, pruning shears, boxes, baskets and paper and/or canvas bags. Although
plastic bags may be used for collecting, storing seeds in airtight containers or plastic bags will
encourage mold growth. Many plants can be stripped by hand or the seed can be beaten onto
drop cloths.
Collecting seeds at the correct time is crucial for propagation to be successful. Gather fruits from
the ground only if they have recently dropped. Reject any fruits or seeds that have been on moist
ground for some time or any seed that may have started to decay or become infested with insects.
They could contaminate the rest of your seed harvest if combined with other seeds during storage.
Delayed harvesting of species with persistent pods often results in insect-infested seeds.
Proper harvesting is aided by an understanding of seed ripening, dispersal mechanisms and the
influences of weather on the timing of seed maturation.
Flowering and fruiting dates vary from year to year. Familiarize yourself with the approximate
flowering and fruiting dates and be able to recognize mature fruit or seeds. An early spring and
dry summer, for example, may cause seeds to set early. Seed quality also varies from year to year
and from location to location.
Mature seeds are usually dark in color, firm and dry. Seeds that are green and moist are immature
and will generally produce unhealthy seedlings or fail to germinate. The flesh of pulpy fruits often
becomes soft and changes from green or yellowish to reddish or blue-purple when ripe.
Seeds are often mature a week or more before the fleshy fruits turn color and fall from the plant.
You can determine seed maturity by cutting open the fruit and examining seeds for firmness, fullness
and dark color. A delay of only a few days may be the difference between success and failure in
collecting a good crop, especially for those species with seeds that are dispersed quickly or that
are attractive to birds and other animals.
Many pods or capsules dehisce, they open and expel seeds, when ripe and mature
at staggered intervals, making collection difficult. Once maturation begins, check it every few days
to collect any newly matured seeds.
You may also try inverting a paper sack over the immature seed and tying it off with string. Enough
light and air will reach the plant to allow it to continue growing, and the sack will hold the seeds as
they mature and drop; with this strategy, you only have to collect seeds once, at the end of seed set.
Seed pods should be dried in single layers spread thinly on canvas cloths, screens or trays elevated
from the ground. Curing on the pod may take longer for species other than legumes. Air-drying takes
1 to 3 days, depending on the humidity.
After the seeds have dried, you can extract them from the pods by beating or threshing. A mature pod
will often twist and split open to drop the seeds.
Although not all seeds need to be cleaned before storage, those with pulpy fruit should be cleaned to
prevent mold. Remove the pulp of large fruits by hand by rubbing on a screen or mashing with a wooden
block, rolling pin, or fruit press being careful not to damage the seed.
You can clean smaller fruits with a blender, as long as you are careful not to damage the seeds. Blend
a small amount of the seeds in a two to one ratio with water. Use brief, intermittent agitations at low speed
and then strain the mixture to separate the seeds from the pulp.
Most seeds mature in the fall and are intended to germinate the following spring. It is often
necessary to persuade a dormant seed that it has been through a winter. The exact requirement
for each species can be looked up, but the commonest is cold damp stratification. This means
moistening the seed and placing it in a cold environment for 1 or more months before planting.
Seed Stratification
Stratification is a process of treating seeds to break seed dormancies
and initiate the germination process in spring.
Thrashing seeds, separating seeds from the rest of the collected plant material is optional.
The easiest way to thrash seeds is to rub the collected material against a coarse screen with a gloved hand.
Thrashing seeds does have at least 2 advantages:
1. It reduces the volume of seeds to be stored.
2. It saves on storage space and deters insect eggs, mold spores and other seed-disease vector, most of
which are removed and discarded along with the chaff.
Seed pods should be dried in single layers spread thinly on canvas cloths, screens or trays elevated
from the ground. Curing on the pod may take longer for species other than legumes. Air-drying takes
1 to 3 days, depending on the humidity.
Store seeds in the refrigerator, not the freezer, until you are ready to plant. Low temperature, humidity
and light level protect seed longevity. If it is not practical to store seeds in your refrigerator, store them
in any place that is cool, dark and dry, protecting them from insects as much as possible.
Store the seeds in paper sacks to allow good air circulation and prevent molding. It is important to
include basic information on labels, including date of collection, species name, location of collection
and name of collector.
Do not store seeds in plastic bags or other non-breathable containers unless they are air-dried
thoroughly first.
Dusting the seeds with a mild insecticide will help prevent insect infestation and kill any pests
collected with the seeds. Or, you can insert a pest strip for several days while leaving the paper
bag open to allow insects to escape. Freezing the seed for a brief period may also be a viable
alternative.
Seeds of fleshy fruits should be kept moist to maintain viability. If allowed to dry out, they will either
germinate prematurely or not at all. This type of seed should be planted immediately or mixed in a 1:1
ratio of moist sand or in a vermiculite or perlite mixture (depending on seed size), and stored in a
cool place.
If the root emerges from the seeds during storage, the seedling should be removed and planted
immediately.
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