Dormancy is an embryo condition that keeps a seed from germinating before it is ready. Internal dormancy occurs because the seed is not chemically ready to germinate. Seed-coat dormancy or external dormancy is caused by a hard seed coat that does not allow water or oxygen to reach the embryo. Stratification is used to break internal dormancy in seeds by exposing them to cold, moist conditions. This simulates natural conditions when seeds fall to the ground and overwinter in moist litter and soil.
Stratification protects plants by preventing seed germination during cold winter months.
When warm weather arrives, stratification requirements have been satisfied and the seeds germinate safely. Some species need long periods of stratification and others need none. In some cases, stratification is not necessary but will greatly reduce the time needed for seeds to break dormancy. In scarification, hard seed coats are weakened by mechanical abrasion and other forces. Natural scarification occurs as seeds pass through animals' digestive systems, fungi slowly break down the seed coat, and the seeds freeze and thaw.