Stratification (seeds)

In botany, stratification is the process of soaking and chilling seeds, most commonly those of trees and shrubs, prior to sowing. It simulates natural conditions where the seeds would remain all winter on cold wet ground. Seeds will germinate promptly and uniformly after stratification. Unstratified seeds may take up to two years to germinate, if they are able to germinate at all.

Many tree seeds have what is called an "embryonic dormancy" and generally speaking will not sprout until this dormancy is broken.

In the wild, "seed dormancy" is usually overcome by the seed spending time in the ground through a winter period and having their hard seed coat soften up a bit. 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. In its most basic form, when we control the cold stratification process, the pretreatment amounts to nothing more than subjecting the seeds to storage in a cool (not freezing) and moist environment for a period found to be sufficient for the species in question. This period of time is often and usually found to be somewhere between 1 through 3 months.