The winters are cold in Minnesota. In order for native seeds to survive the winter, they go dormant, and when the days start to warm in the spring and the ground thaws, they come out of their dormancy and germinate. The process of replicating this winter dormancy in order to germinate the seeds on your own is called stratification. Many seeds require different amounts of time for stratification. If you’re planning on participating in stratification, check online or on the seed packets for that information when you first purchase them. If you are hoping to grow native plants from seed, which is the most cost efficient way to get native plants in your garden, there are a few ways to stratify them.
One way to stratify these seeds would be to plant the seeds outside in the fall, before the ground starts to freeze. This is the closest way to replicate natural conditions, and requires little money, time, and space. The disadvantage is that the seedlings will be exposed to the elements early on in their growth, and may have a harder time becoming established. It’s still a great method that Garden Manager Louis employs at Mashkiikii Gitigan for several of our seeds.
Another method is called artificial stratification. It involves replicating the cold period by placing the seeds in a moist growing medium and into the fridge for an extended period of time. There’s a few ways to do this, but Louis likes to plant the seeds into the seed trays that he would like them to grow in, water that soil, and put it in the fridge with some sort of cover on the tray to keep the humidity in so the seeds don’t dry out. Louis uses a humidity dome.
When you take the seeds out of the fridge, all you have to do is place the tray under the grow lights and the seeds should start germinating. Another way would be to place the seeds in a damp paper towel, put the paper towel into a plastic bag, and place that in your fridge. Once you take it out of the fridge, you can plant the seeds into soil in seed trays under a grow light, or plant them directly outside. Planting outside gives you the advantage of not needing to buy grow lights and dedicate space in your house for seed starting, but again the seeds might be delicate when exposed to the elements.
Stick to the stratification time that the seed packet/internet suggests, but if you ever see the seeds germinating in the fridge, take them out immediately and put them under the light!
Most of the native plants we grow at Mashiikii Gitigan need a stratification period, so we are currently stratifying and growing plants like Milkweed, Echinacea, Rudbeckia, Vervain, Red-Osier Dogwood, and Wild Bergamont.