Collecting Native Plant Propagules

Gather Seed

Gathering seed is the first step, and it may also be the last step if you are delivering the propagules immediately to a nursery for growing out. Only collect as much as you need and not so much that the reproduction of the population is affected. Traditionally, a maximum of one-third of the seed was the rule-of-thumb. More current references suggest from one-fourth to as low as 5%.

Seeds should be collected when they are thoroughly dry, if possible, using paper bags or paper envelopes. Do not use plastic bags for gathering seeds. The plastic creates static cling that is a real problem for very tiny seeds. Plastic also prevents the necessary drying process and will create mold and rot the seeds. Moisture from rain or dew can ruin seeds very quickly.

Seed collection of native plants and wildflowers is done primarily by hand for several reasons;

• most seed to be harvested will not be growing in pure stands and as the topography varies it severely limits mechanical equipment use.
• There is also limited mechanical equipment available which most of us could not afford and
• the fact is that large machinery is apt to tear up the very landscapes that you want to preserve.

So the majority of equipment we use is makeshift and site- or plant-type specific. For example, collecting the seeds of most grasses can be done by stripping the culms (the flowering shoot) off the stem. This can be done by hand or with mechanical fingers of sheet metal.

Collecting Equipment

Basic equipment needed to collect seeds includes gloves (good ones), boots, drop cloths, pruning shears, boxes, baskets, and paper or canvas bags (plastic bags will allow the seeds to get moldy more easily). Numerous references cite a good pair of gardening gloves as the best tool. A tray of some kind (like a flat cake pan) can be used to collect the seeds of herbaceous wildflowers.

Method for harvesting seeds depends on the type of plant.

Grass seeds and plants with a spike-like inflorescence (the flowering shoot)

are collected by stripping the flowering culms off the stems. The seeds are inside the inflorescence of the flowering culm. Running your fingers up the stem is usually the easiest way to collect grass seeds.

Plants that have spiny thistle-like seeds

should be collected as an entire seed head.

Plants with fleshy seeds

should be picked by hand.

Some seeds such as columbine

are very easy to collect. The pods are urn-shaped and open when ripe, revealing the seeds in their little cups. Just bend the stalks a bit and tap the pods over a bag or tray. The seeds will fall out.

Plants with seeds in pods or capsules

may be collected by picking the entire pod or capsule. If there are many pods on a single stalk, you can pick the ripe ones every day, or you can cut off the entire stalk when the first few seed heads or capsules are fully ripe. Put the stalks or pods in a closed paper bag. The pods will pop open when ripe and the seeds are easily poured out of the bag. Don't put too many stalks in the bag, as overcrowding reduces the air circulation and induces mold.

These are just a few ideas for collecting native seeds. Time, patience, and experimentation will lead to good results.

Separate

Whatever the species, native seeds should be cleaned of debris, air-dried if necessary, and then planted or stored. There are a few species that should be planted as soon as they are ripe and not allowed to dry at all, but these are exceptions to the rule. If you deliver the seeds immediately to the nursery, they may perform the preparation for you, but if there is a delay in delivery you may need to perform some of the urgent procedures to prevent spoilage - these steps are underlined below. Of course, if you are storing or planting the seeds yourself, the job falls to you.

Cleaning equipment

Various kinds of machinery can be used to clean the seeds after collection. A tumbler that threshes grass seeds can be used to separate the seeds from other plant parts or a blender can separate fleshy seeds from the pulp. Screens with various size openings are helpful to separate seeds from other plant parts. If only a few hundred seeds at a time need to be cleaned, a seed cleaner can be made with a newspaper. Fold the paper lengthwise and grasp the folds. The seeds can be separated from the chaff by gently inclining the paper while blowing on the material and shaking the paper. this usually results in seed that needs only a single screening.

Seeds in dried capsules

may be harvested from the capsules or the capsules can be crushed, if the seed is sufficiently hard, and sown with the seeds.

Grass seeds

A simple threshing method is to rub the collected material against a coarse screen with a gloved hand, Another way is to use a paddle with a rubber matting over it. A techniques for grinding open non-splitting pods is to use bricks. Place the matter between two bricks -be sure to leave some stems in the matter to insure you do not crush the seed.

Seeds of most cones

are released by drying the cones to open them, shaking the seeds out, separating seeds from scales and debris, loosening the seed wings. and finally separating clean, full seeds from wings, dust, empty seeds, and other small particles. As soon as the sacks of cones are brought in they should be emptied as immediate aeration is needed when cones are wet and green. The partly dry- long enough to congeal the pitch- cones can then be tumbled to remove the sticky pitch from the seed. Storage of cones at low temperature is necessary for some species but freezing must be avoided while other species need high temperatures of up to 170 deg before they will give up their seed..* R

Wildflowers that produce many seed heads or capsules on a single stalk.

Store these stalks in tall paper bags indoors, leaving the bags open at the top. This will allow good air circulation and prevent the seeds from becoming moldy. Check the stalks from time to time, and shake them vigorously inside the bag so the seeds will fall out of the capsules. Seeds that fallout can be carefully poured out of the bag while the rest continue to ripen. There is usually enough nourishment and moisture in the stalks to allow most of the seeds to ripen.

Geraniums

have pods that pop so vigorously that the paper bag should be closed while the seeds are ripening. Don't put too many stalks in the bag, as overcrowding reduces the air circulation and induces mold.

Lupines

have very fleshy seed pods that will turn moldy in only a few days if they are put into paper bags. These pods should be thinly spread out in shallow boxes that are tightly covered with bridal netting. This netting is inexpensive and can be purchased at any fabric store. The netting allows good air circulation to prevent mold and the seeds will fall to the bottom of the box when the pods pop open.

Wildflowers that have berries or fleshy fruits

require special treatment. Extracting the seeds is a difficult chore and techniques vary with each species. Whatever the species, these seeds should have all the fleshy parts removed. These seeds should then be thoroughly cleaned and air-dried before planting or storage.
Some berries can be temporarily packed in sealed plastic bags and left at room temperature until the fruits rot and turn brown or black. This smelly mush can then be put into a strainer or colander. Rinse thoroughly under tepid running water to wash away the flesh. Mashing the pulp with a wooden potato masher or wooden spoon helps to separate the seeds from the pulp. These seeds should then be completely air-dried. For these fleshy seeds use wooden potato masher or wooden spoon for drying rather than paper towels. Unless every speck of pulp is removed from these seeds they will stick to paper towels like glue.

Seeds with fleshy covering

are sometimes dried and planted with the skins intact. After cleaning and washing the fruit may be spread on trays and dried in the sun. However, the mummified fruit may contain germination inhibitors and provide a nutrient rich substrate for micro-organisms during germination.

Drying

Moisture from rain or dew can ruin seeds very quickly. If seeds must be collected when they are wet they should be spread out in shallow boxes to air-dry indoors. Shoe box lids are excellent for this purpose, and can be lined with paper towels or tissues to absorb the moisture.

It is also a good idea to air-dry most species of seeds that have been hulled. Dishes (not plastic) or shallow boxes work equally well as long as they are big enough to spread the seeds out in a single layer. This not only prevents spoilage but also allows tiny insects to escape or be destroyed before the seeds are packed for storage. Cleaning and drying the seeds carefully will insure good results. Seeds that are stored in their pods or seed heads will usually harbor insects and their eggs and larva that over time will destroy most of your collection.

Storage.

The next step is storing the seeds.

The fresher the seed, the better the chances of germination.

Although information may be available on optimal seed storage for specific species, the following guidelines can be used in storing most seeds.

For the short-term, store seeds in paper bags. This allows air circulation and prevents mold. Low and constant humidity and temperature (less than 50 degrees Fahrenheit and less than 65% humidity) is ideal. If a potential problem is apparent, using a mild insecticide or fungicide may be advisable . Fleshy seeds should be planted as soon as possible and kept moist once clean. If these seeds dry out, they will lose their viability or could possibly germinate. Storing them in a one-to-one ratio of moist sand-sphagnum moss or peat-perlite mixture is the best option.

Seeds can be stored in paper or glassine envelopes or glass vials. Plastic vials from prescription medications can sometimes be used, but they are not recommended for very tiny seeds as static will cause tiny seeds to cling to the sides of the container, making them difficult to remove. Packed seeds can be placed in glass jars or coffee cans stored in the refrigerator until planting time. If coffee cans are used they can be left outdoors in a protected spot during the winter. The alternate freezing and thawing of outdoor temperatures actually increases the percentage of germination of some seeds.

The two most important factors affecting seed longevity are seed moisture content and temperature. Two rules of thumb are

1. each 1% reduction in seed moisture doubles the life of the seed.
2. Each 10 degree (F) reduction in seed temperature doubles the life of the seeds.

To store seed properly for the long-term, the seed should be dried to the moisture content desired. For one season's storage, the seed should be dried down to at least equilibrium with 65% relative humidity. For 2-3 years storage, seed should be dried down to equilibrium with 45% relative humidity. For long term storage after packing in moisture proof containers, the seed should be dried to EQ 25%. Too rapid drying is dangerous. If the moisture gradient from the seed surface is steeper than the moisture gradient from the interior of the seed to the surface, the surface will dry rapidly,resulting in cracking of the tissue. For some seed too rapid drying causes the outer cells to shrink, becoming impervious to moisture. Caution: extra care must be taken when handling dry seed because they are more susceptible to injury.

The best storage is in a cool and dry environment away from rodents or insects. Clean garages, basements or even refrigerators work well for this purpose.

Exercises

1. In a classroom setting, you can practice stripping seeds from grasses, grinding with bricks to remove hulls, and assembling storage vials, provided suitable seeds are available.

References

• Basic
  Collecting Wildflower Seeds, Betty Knorr, Ph.D., Native Plant Society of New Jersey
  http://www.npsnj.org/collecting_seeds.htm
  Wild Seeds, Illinois State Museum
  http://www.museum.state.il.us/muslink/prairie/htmls/ga_wildseeds.html
  Seeds of Wildland plants by Young and Young
  1986 Timber Press inc.
  Hartmann, H. T. and D.E. Kester. 1983. Plant propagation principles and practices.
  Fourth Edition. Prentice-Hall, Inc.: Englewood Cliffs, NJ.
  Seeds of woody plants in the United States. Agricultural Handbook No. 450.
  1974. Forest Service, U.S.D.A.: Washington, D.C.
  Collecting Wildflower and Praire Seed, University of Minnesota Sustainable Urban Landscape Information Series
  http://www.sustland.umn.edu/implement/wildflower.htm
  Ref *source Seeds of Wildland plants by Young and Young 1986 Timber Press inc. source:http://www.npsnj.org/collecting_seeds.htm source:http://www.museum.state.il.us/muslink/prairie/htmls/ga_wildseeds.html Hartmann, H. T. and D.E. Kester. 1983. Plant propagation principles and practices. Fourth Edition. Prentice-Hall, Inc.: Englewood Cliffs, NJ. Seeds of woody plants in the United States. Agricultural Handbook No. 450. 1974. Forest Service, U.S.D.A.: Washington, D.C. Ref http://www.hcs.ohio-state.edu/mg/manual/prop2.htm Sources:http://www.sustland.umn.edu/implement/wildflower.htm
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The content of the page was last modified 2008-05-06