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The Garden Plot for January 25, 2008
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “Seed Dormancy”
All the flower and vegetable seeds I ordered are arriving in the mail. Some perennial flower seeds and some of the native plant seeds I collected last summer require special seed treatments before they will germinate. Even if these seeds are given favorable water and temperature conditions, they may still fail to germinate due to a mechanism called “seed dormancy”.
Seed dormancy keeps seeds from germinating in unfavorable conditions (dry, hot, cold, etc.). Dormancy also allows populations of plants to distribute the germination of their offspring over many seasons. So, if extreme environmental conditions occur and seedlings die, there is a store of seed to germinate later. In tough environments, such as Western Montana with extended cold and dry periods, a seed that will not germinate when first presented with optimum moisture and temperature conditions has an adaptive advantage. For example, if a seed germinated during a warm spell in late winter, it would be killed when cold weather resumed. If a seed germinated as soon as it was mature in July, as a result of a rainy period, it would dry out and die during our hot, dry August weather.
Seeds from the majority of our annual garden plants do not show dormancy. Humans have selected against seed dormancy by saving the seeds of plants that germinate quickly and easily when provided with favorable conditions. Most native plants, however, have some kind of dormancy.
There are several techniques to overcome or break seed dormancy. The two main techniques are seed scarification and seed stratification. Scarification is the breaking of an impermeable seed coat so that moisture can enter the seed. This can be accomplished by rubbing seed over fine sandpaper, or by carefully soaking in an acid such as sulfuric acid. Seed stratification is the practice of placing seeds in a moist medium for a period of time. Place seeds between moist paper towels or mix them with moist, but not wet, sphagnum peat moss. Cold moist stratification at temperatures of 34˚F to 45˚F is most common.
Sometimes the only inhibition on seed germination is a thick, hard, and impermeable seed coat. Removing the seed hull or outer covering, greatly improves germination without scarification.
There are a few other more common seed germination tricks. Small seeded species often require light to germinate. This prevents small seeds from germinating deep in the soil where they would not have the energy reserve to elongate to the surface. For example, Columbine, Silvermound, and Bellflowers all require light for germination. So, cover these seeds only very lightly, or not at all, when germinating. On the other hand, some species, such as Batchelor’s Buttons, require darkness for germination.
For more information on seed germination requirements contact your local county extension agent.
Helen Atthowe's new short program of gardening tips
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