Cold Stratify

Cold Stratify

Cold Stratify

Many wildflowers—especially native varieties—have clever mechanisms in place that help protect them from germinating too early in the spring or too late in the summer. These varieties re-seed naturally in the wild and stay dormant until the proper time for them to start sprouting. More and more gardeners are seeing the benefits of growing native varieties in their landscapes and with a simple technique called cold stratification, you can easily add these wildflowers to your garden in the spring.Cold stratification is an extremely easy process and once you’ve done it once, you’ll no doubt get the hang of it. The first step is to gather the materials needed, all of which can be found in your home, tool shed, or with a quick trip to the hardware store.



In the wild, seed dormancy is usually overcome by the seed spending time in the ground through a winter period and having its hard seed coat softened by frost and weathering action. By doing so the seed is undergoing a natural form of "cold stratification" or pretreatment. This cold moist period triggers the seed's embryo; its growth and subsequent expansion eventually break through the softened seed coat in its search for sun and nutrients.Any seeds that are indicated as needing a period of warm stratification followed by cold stratification should be subjected to the same measures, but the seeds should additionally be stratified in a warm area first, followed by the cold period in a refrigerator later. Warm stratification requires temperatures of 15-20°C (59-68°F). In many instances, warm stratification followed by cold stratification requirements can also be met by planting the seeds in summer in a mulched bed for expected germination the following spring. Some seeds may not germinate until the second spring.

In essence, cold stratification mimics the winter season’s chilly, moist weather that triggers a seed’s sprouting from a dormant state. Most perennial plant seeds (such as native wildflowers) require this combo of cold and damp to germinate. In nature, this occurs–well, naturally, of course while the butterflies snooze or cruise for the winter! But you can accomplish the process yourself. The cold temperatures are as close as your refrigerator, and the moisture of the equation is supplied by water. By doing the cold stratifying yourself, you keep the young seeds safer from any animals that might eat them and make it less likely that they’ll succumb to rot or mildew from excess water. Germination is also accelerated.Dry stratification is a seed pre-treatment in which the seed is subjected to cold temperatures of 32ËšF or lower, for a period of a month or longer. This simple treatment of keeping the seeds in cold, dry storage helps increase germination rates by immitating a natural winter dormant period. Many native prairie species require only Dry Stratification. This can be accomplished in temperate climates by storing the seed in Ziploc bags in a refrigerator, or in a rodent-proof container in an unheated building over winter for 30-120 days (depending upon the species). Most warm season prairie grasses and wildflowers require only 30 to 60 days of dry stratification to break seed dormancy. (Source: www.prairienursery.com)



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