Stratification


 o 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.

 o Faux Winter

In most cases, what is needed is a little faux winter. It isn't really necessary for the seed to spend the cold months in the ground, as long as it thinks it did. This deception can easily be performed by placing the seeds in a small container with moist (not wet) sand, peat or vermiculite, and leaving it in a refrigerator for four to six weeks. This procedure is known as stratification, purportedly because of the layering of the seeds within the medium.

 o 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.

 o 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 our 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.

-- Sesbania Tripeti


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