Many species of native seeds are dormant and will not germinate until they have experienced a specific set of environmental conditions. This protects the seeds from germinating in the middle of winter and gives them the best chance for survival. Seed dormancy can be broken naturally or artificially using different seed treatments.
To naturally break seed dormancy you will need to sow seeds directly in the ground in the fall. Then the seeds will experience winter temperatures and moisture conditions and germinate in the spring.
To artificially break seed dormancy the seeds can be placed in a moist medium and kept cold in the refrigerator for three months (cold moist stratification). Scroll down for more information on cold moist stratification.
Direct Seeding in the Fall
Fall is the best time of year to sow seeds directly in the ground for most native plant species. If you sow your seeds directly in the ground in the fall you do not need any of the following seed treatments to break dormancy.
Seed Treatment A: No Treatment Necessary
A few native seed species such as Yarrow and Black-eyed Susan do not require any special treatment before sowing. Plant seed in spring either directly in the ground or sow in pots for transplanting later.
Grasses require 90 days of cold dry stratification before sowing. We store our grass seed under these conditions and is ready for sowing.
Seed Treatment L: Needs Light to Germinate
Some native seed species such as White panicled aster and New England aster require light to germinate. Sow directly on top of the soil and keep moist until germination. If you are sowing the seed in pots you can sprinkle the seed with a thin layer of vermiculite after sowing.
Seed Treatment C: Cold Moist Stratification
Another method for growing native plants from seed involves creating cold, moist conditions (so the seeds will experience a winter season) and then sowing the seeds in pots or outside if conditions are suitable. Species such as Blue vervain and most sedges require cold, moist stratification.
The most common dormancy breaking treatment for native seeds is cold moist stratification. This method creates a cold, moist environment for the seeds (usually for one to three months) by placing the seeds in the fridge.
Small plastic bags, vermiculite, coffee filters, seeds, water, pencil or permanent marker.
First, you should label your coffee filter with the name of the species and the date (or you can label the plastic bag).
Then you will add moistened vermiculite to the plastic bag. Try not to add too much water, there should not be excess water at the bottom of the bag.
Next, you can place the seeds in the coffee filter, or you can put the seeds directly in the vermiculite. After the cold moist treatment you can sow the seed-vermiculite mixture.
Then place the coffee filter with the seeds into the plastic bag with the vermiculite, making sure that the coffee filter is in contact with the vermiculite. The coffee filter should soak up water from the vermiculite and become damp.
Make sure that the bag has air in it, the seeds need to breathe!
Finally, place the plastic bag in the fridge. Check periodically to ensure that the vermiculite does not dry out. Plant immediately if the seeds begin to germinate.
After three months, remove the bag from the fridge and plant the seeds.
After stratification the seeds will be moist and stuck together on the filter paper.
In order to made it easier to spread the moist seeds evenly you can mix them with a small amount of sand before spreading them over the soil.
There are other methods of cold moist stratification. The important thing to remember is to keep seeds moist at refridgerator temperature for the appropriate amount of time in order to break dormancy.