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Stratification
Giving Seeds Their Wakeup Call
As gardeners know all too well, as soon as the soil warms in spring,
there will be a plethora of new weeds to contend with. These are the
progeny of last year's flowers, and they have bided their time until
conditions were just right for germination. By delaying germination until
spring, they will maximize their growth before having to contend with
their first winter. Seeds use various chemical and mechanical means
of inhibiting germination until the time is ripe.
But not all seeds go through a dormant period. Most seeds sold
commercially through catalogs and nurseries have been hybridized for
generations and will usually come up as soon as planted. Where the
gardener is likely to encounter problems is with seeds of native and
woody plants. But for seeds with thick, hard walls, even commercial
seeds may need some help.
Faux Winter
In most cases, what is needed is a little pretend winter.
It isn't all that necessary for the seed to spend the cold months in
the ground, as long as it thinks it did. You can easily deceive
them by placing the seeds in a small container with moist (not wet)
sand, peat or vermiculite, and leaving it in the refrigerator for
four to six weeks. This procedure is known as stratification,
evidently because of the layering of the seeds within the medium.
Cutting to the Quick
For seeds with hard coats what's needed is a little nick in the pants.
This is known as scarification. While in natural conditions this
coat would eventually be broken down, the impatient gardener can speed
the process by using a knife or file to make a shallow cut. This will
allow moisture to enter and the seed to germinate. For instance, the
large, hard seeds of the moonflower vine, Ipomoea alba,
rarely germinate unless their coat has been notched.
For other seeds, immersion in warm water will often do the trick.
Seeds like those of the native columbine of the eastern U.S.,
Aquilegia canadensis, need to be exposed to a certain
amount of sunlight before they will germinate.
Finding What Works
So how do you know what procedure a particular seed needs? Well, the
best way is to find a book that covers the type of plants you are
trying to propagate. Or, you can be a true cyber-gardener, and post a
message to the
Growing from Seed Forum. Much of the advice you find will be based
on the experience of trial and error. And often one authority
contradicts another. But gardening isn't meant to be a purely logical
pursuit. For most of us, the learning is the fun.
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