In
horticulture,
stratification is the process of pretreating
seeds to simulate natural conditions that a seed must endure before
germination. Many seed species have what is called an
embryonic dormancy and generally speaking will not sprout until this dormancy is broken.
Example:
For seeds of
trees and
shrubs from temperate climates, stratification involves soaking and chilling
seeds prior to
sowing. This simulates natural conditions where the seeds would remain through a winter on cold, wet
ground. Seeds will usually germinate promptly and uniformly after stratification. Unstratified seeds may take up to two years to germinate, if they do so at all.
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 softened up 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.