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Seed Stratification
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Seeds are usually the best method of raising quantities of many kinds of annuals required for bedding displays, such as snapdragons, zinnias, marigolds, stocks, asters and petunias. Many shade and glasshouse plants, such as calceolarias, cinerarias, primulas and cyclamens, are also raised in quantity from seed. It is the only method of propagation for annuals and biennials, which flower, seed and die in either one or two years. Most vegetables are raised from seed, and so are many lawn grasses. Seed Storage If seeds purchased from a seedsman are not sown immediately they should be stored correctly, otherwise the percentage of germination will not be as high as it should be. The seed is a resting stage in the life history of the plant and, although dormant, is alive and capable of developing growth if it is subjected to warmth and moisture. Under natural conditions seeds fall from the parent plant and spend their resting period among fallen leaves and loose soil, often being frozen or in a fairly low temperature; when warmth and moisture arrive with the spring, germination starts. The storing of seeds under dry and warm conditions is, therefore, unsuitable and can result in loss of viability or growing power. Store packets of seeds in a cool, airy placeâ€â€not in an airtight container. The ideal spot is one of fairly even temperature, warm enough to dispel dampness. Seed Types Seeds vary considerably, not only in size and shape, but also in their formation. 1. Small, Dust-like Seeds Begonias, calceolarias, eucalypts, bottlebrushes and lobelias provide examples of these seeds, which should be sown thinly on a surface of soil or other suitable medium that is very fine and perfectly level. Many gardeners do not cover such tiny seeds but merely press them into the surface. If any covering is given it should be a mere sprinkling of fine sand or sandy soil. To make thin sowing easier, mix a small quantity of fine, dry sand with the seeds in the packet to serve as a carrier and to ensure an even spread as the seeds are scattered. If sowing indoors cover each receptacle with a pane of glass to conserve moisture, and put a sheet of paper on top to reduce the light. 2. Fleshy Seeds Acorns and beans are two fleshy seeds. Some fleshy seeds become hard externally and have a hard skin or seed coat, especially if they have been stored for any length of time. They should be soaked in water, preferably tepid, for 24 hours or more before sowing. This will soften the seed coat and help the process of germination to start. 3. Hard-Coated Seeds Seeds such as those of acacias, dark-coloured sweet peas, the various nuts such as the walnut and almond, and others having a hard outer shell, need pre-sowing treatment to ensure reasonably quick germination. If sown without treatment the seeds may remain dormant for a long time or fail to germinate. To make sure that the hard seed-coats do break down and that moisture enters to start the seeds germinating, chip the outer casing of the seeds with a knife, or file or rub them on a rough surface. The filing or chipping should be done carefully and on the opposite side to the "eye" of each seed, or the embryo or "germ" may be damaged. On most seeds the eye can be seen fairly easily, because it is the point where the seed was attached in the seed pod. Some hard seeds such as those of acacias are best treated by covering with boiling water and allowing to soak overnight. 4. Oily Seeds Some seeds have an oily content, and because of this do not retain their viability as long as others. Good examples are those of carrots, parsnips, celerys, castor beans, magnolias and camellias. Do not store these seeds in a warm place for any longer than is necessary, because once the oil dries up, the seeds shrivel and will fail to germinate. For this reason it is unwise to retain parsnip and carrot seeds for a second year: old seeds are likely either to fail completely or to provide very poor germination. 5. Composite or Multiple Seeds Some plants produce several seeds together within a dry or fleshy case. The beet is a good example of a dry case which contains several seeds. Thin sowing or sowing in hills is essential because three or four seedlings usually arise from each multiple seed. The cotoneaster, holly, hawthorn and crab-apple are some of the shrubs and trees that produce fleshy and often highly coloured fruits with a number of seeds embedded in the pulpy mass. |
  
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