Stratification is a means of simulating the chilling and warming that seeds would endure if left outdoors in their native climate, for the winter.
Some seeds will stay dormant until triggered by a certain amount of time in cold temperature or warm, damp conditions. This will occur naturally if the seeds are left outdoors or in a coldframe throughout the winter. Gardeners can break the dormancy of these seeds by mimicking the required conditions indoors.
To stratify seeds, store the seeds in some moistened peat, sand or paper towel in a closed container or sealed plastic bag. For cold stratification, place the container in the refrigerator. For warm stratification, store it somewhere where the temperature remains between 68 to 85 degrees F.
The length of time needed to stratify depends on the type of seed. Be sure to check every once in awhile to make sure there is still some moisture in the container.
Some seeds, Baptisia, may need both stratification and scarification.