Stratification, or pre-chilling, is the process of refrigerating seeds prior to sowing. This simulates the low temperatures of winter and encourages more even germination after the seeds are sown. There are two easy ways to stratify seeds. The first is to place seeds between wet paper towels, slip them into a plastic bag, and place them in the freezer for several days. Alternately, seeds can be planted in peat pellets or other growing medium and placed outside to chill for 7 to 10 days in winter. They are then brought indoors, where they should germinate evenly. In some instances, un-stratified seeds may take as long as several years to germinate.