You may be wondering what is scarification and why some seeds require it. Scarification is the process of intentionally damaging the outside of a seed coating so that the seed “wakes up” and knows that it’s time to start the germination process.
It’s not a necessary process for all seeds, so check to see if your seed actually needs scarification. Your seed packet will let you know if you need to rough your seeds up a little bit.
Seed scarification in nature
Seeds that need scarification have adapted to develop a tough, waterproof, and gas-proof seed coat. The seeds lie dormant through winter, where they are subjected to natural forms of scarification. Freezing temperatures cause the outer coating to expand and contract until it is damaged enough for water to get through. Wind, rain, and the footsteps of humans and animals cause wear and tear that scuffs up the seed coat. Some seeds are naturally scarified by going through the digestive system of birds and other animals that eat them. The seed coats definitely have to be strong to protect the plant embryo until spring.
Seed scarification for the home gardener
For the home gardener, scarification requires a gentle touch. Nick the seed coating with a file, a knife, or by lightly roughing up the outside with some sandpaper. Your goal is to barely crack the outer coating, but not damage or crumble the seed within. Another technique is to put your seeds into a jar of gravel; or sand and shake to mimic the natural conditions that would naturally nick the seed coating.
Stratification is similar to seed scarification and can also improve germination rates in some seeds. Cold-stratified seeds are kept in temperatures for an extended period of time to simulate the cold and wet of winter. Milkweed is an example of a seed that needs cold stratification. The change in temperatures acts as a signal that it’s time to wake up from winter dormancy.
Other seed scarification methods
There are other methods of scarification used. Sometimes commercial seed is pretreated with chemicals to thin the seed coating. Another method is hot water scarification, where water is brought to a boil. The seeds are added and then allowed to cool down and planted thereafter.
Mechanical scarification is the most practical method for the home gardener, with a better chance of success.
Scarification may sound scary, but it’s a natural process that some seeds require. Just remember that once you’ve appropriately roughed up your seeds, you need to plant them immediately. That seed coat is no longer protecting the baby plant within, so it’s important not to delay. For those seeds that need it, taking a little time and effort to nick the seed coating will greatly improve your chances of germination.
Written by Teresa Chandler