Scarification vs Stratification
Germination occurs when water enters the embryo of the seed, igniting metabolic processes that are suspended during dormancy. Proper temperature, growing medium, and availability of water and oxygen are necessary for germination to occur. Some seeds germinate at different rates because of their diverse genetic portfolio.
Seed dormancy is a naturally occurring adaptation which delays germination until favorable growing conditions arise that will increase the likelihood of plant survival. It is a built-in technique which allows seeds to wait out unfavorable conditions until the best conditions for survival arise.
Delayed germination prevents all seeds from simultaneously germinating at the same time, increasing the overall survival of the group. It lessens individual competition and risk of death due to environmental factors.
These are methods humans can use to induce germination in an agricultural or landscape setting, forcing nature to speed up its normal processes. They help to remove the inhibitors of germination, and speed along mother nature’s timeline. Scarification and stratification mimic the naturally occurring environmental cycles that break down the outer coat of the seed enough to allow them to germinate. Some of nature’s methods that prepare a seed for germination include exposure to cold by overwintering on the ground, precipitation, physical stressors, and going through an animal’s digestive tract.
Scarification
Scarification involves physically breaking down the tough seed coat to allow water and air inside to start the germination process. You can accomplish this by nicking with a knife or file or abrading with sandpaper just enough to expose a bit of the inner portion of the seed.
Stratification
Stratification is a pre-treatment for seed that mimics what the seeds would experience in the soil over winter and can be either “dry” or “moist”. Dry stratification is when seeds are subjected to temperatures below 32F for a month or longer. Seeds are placed in a dry Ziploc bag and put in the freezer for up to 2 months. Many warm season prairie grasses and flowers will take 30-60 days of dry stratification to break dormancy if using this method.
Moist stratification mimics a cold, damp winter. Seed is mixed with moistened growing medium such as vermiculite, sand, or peat moss, and placed in the refrigerator from 10 days to 3 months. If fall seeding annual wildflowers, stratification is not required as dormancy will be broken naturally over the winter.
To break dormancy or not?
But humans like to take things into our own hands! Scarification and stratification are ways to bypass nature’s insurance plan and cause germination on our preferred timeline. You cancel this insurance plan when you use these methods, so be sure to provide your new plant babies with extra care until they are established enough to tough it out on their own.
