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Seeds
The choice, care and handling of seeds
Germination requirements of SeedsThe qualities, characteristics and forms of the seeds produced by plants vary greatly according to species or variety and environment. Some seeds are ready to germinate right after they are produced and others need a period of dormancy or a period of cold before they will grow.Some seeds grow quickly, and some take a long time to reach maturity. The way you harvest, ripen and store seeds depends upon their germination requirements and the factors that influence the dormancy of each type of seed.
To dry or not to dry?For example, some seeds, including many tree seeds, must never be allowed to dry out before planting. For shipping these seeds should be collected as soon as they are ripe and carefully packed so they cannot dry out. For most other seeds, when saving seed, it is best accomplished by placing them in a dry, dark place. Some seeds may require scarring or a special cold treatment before they will break dormancy and germinate.
Dormancy requirements of SeedsThere are several reasons that a seed remains dormant. Some, such as those of walnut, olive, peach, plum, lettuce, and many flowers and shrubs, have very hard coats which must be injured before they begin to absorb water and germinate. In nature, winter heaving and weathering scarify the seeds, but the gardener or grower must do it himself by tapping them with a hammer, filing them or rubbing them with sandpaper.Tropical and desert seedsCertain tropical and desert seeds have an inhibitor in the seed coat and must rest until weather conditions develop which can break down the inhibitor. Seeds of some palms and orchids have embryos so tiny that they must grow during a quiescent period before they are able to germinate.Internal dormancyOther seeds have a rather short period of so-called internal dormancy while they are drying out after being freshly harvested. The dry storage breaks this dormancy, which is a shallow one compared to the deep dormancy of winter-dormant seeds.Deep dormancyDeep dormancy requires long periods of moisture and chilling. Seeds that are doubly dormant need both seed coat and embryo treatments before dormancy is broken. Various shrubs and trees, because of having double dormancy, need two years before they germinate.Cold Treatment (Stratification) of SeedsThe amount of time needed for cold treatment varies. Seed of cedar of Lebanon, which will stay viable for six months, only need two months for stratification. Plants like alder and chestnut need three months; shadblow, horse-chestnut and shellbark hickory need four months. A few plants need both a warm and a cold period of stratification: cotoneaster, bear-berry, dogwood, yews, and some of the bar-berries and junipers. Some lilies, viburnums and the tree peony all need a spell of moderate temperature followed by cold. Unless kept in the refrigerator, such seeds are planted during the summer, kept moist, and allowed their cold dormancy during the following winter.Stratifying seeds in the refrigeratorTo stratify seeds in the refrigerator, mix the seeds with slightly moistened sand, peat moss or sphagnum moss, or a mixture of sand and moss or sand and vermiculite. Store them in polyethylene bags. After a spell in the refrigerator at 40°F. (4.44°C.), watch for the beginnings of germination and when you see the seeds are starting to grow, bring them out and sprinkle them on flats, adding a little water daily so they will stay moist.Storage timeThree months is the usual storage time needed for maples, barberry, birch, bittersweet, flowering dogwood, and fruits like cherries, currants and gooseberries. Two months will suffice for pines, most spruces, false cypress, and arborvitae.Seed Germination
Too much or too little water at the time of germination affects seeds. Celery, for example, needs a great deal of water, but spinach does not. Other seeds that do not need very much water (though a lot does not harm them) include cabbage, turnip, sweet corn, cucumber, onion, carrot, and tomato and many herbs. Those needing quite a bit more are beans, peas, beets, and lettuce.How viable are your seeds?Of course other conditions and the natural longevity of seeds also contribute to the success of germination. Onions are only considered to be viable for a year, along with leeks, parsnips, salsify, and corn; whereas pea, bean, cabbage, and cauliflower seeds will last for three years and melon up to seven years. |
Inspect seedsBe sure to inspect seeds received or saved to make sure that they are clean, all of one kind, uniform in size, and plump and fresh looking. If in doubt, put the seeds through a germination test by scattering a specific number of seeds between two damp towels. Place them in a warm, dark place and, after the required germination period, count how many have sprouted. If it is less than 50 percent, consider using other seed.Seeds need the proper conditions to germinateToo rich a soil in the seedbed is not advisable, and any break in the water requirements of the seeds can be fatal. Also fatal is an inadequate supply of oxygen, which is sometimes brought about when seeds are planted too deep to get good air circulation, or when a very wet season swamps them and cuts off air.
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