Out on the prairie, seeds of native plants drop to the ground every autumn and spontaneously sprout every spring. Nobody is surprised. That’s what wildflowers do.
So why do gardeners sometimes have trouble growing these plants from seeds when they try to get an early indoor start?
It’s precisely because we’re too good to our seeds, taking pains to keep them dry and warm. What these seeds need is the cold and moisture of a typical Midwest winter. That’s their trigger that it’s time to sprout.
Fortunately, it’s easy to supply an artificial trigger. There’s even a name for the process. It’s called stratification. It means, simply, to simulate natural conditions necessary to enable the seeds to break dormancy and sprout. That usually means providing a period where the seeds are both cold and wet. The process is needed not only for prairie plants but for most other perennials and woody plants, too.
Stratification is simple but takes time. How long? It depends on the type of seed.
If you have just a few kinds of seeds, go ahead and plant them in little pots, water the soil, put the pots in a plastic bag, and stick the bag in the refrigerator. If you have a lot of seeds to start, put each kind in a separate plastic bag filled with damp sphagnum moss, then put the bags in the refrigerator. In this case, planting in pots follows the cold treatment.
If my fridge is too crowded, I plant and water the seeds in pots, then stick the pots outside in the cold frame to chill.
How long do the seeds need to chill? It depends. Milkweeds, bluestars, and penstemons, for example, need only about 30 days. Coneflowers, goldenrods, and most kinds of blazing stars require 60 days.
Seed packets often include germination particulars. If not, it’s easy to look up this information. Prairie seed catalogs sometimes offer charts with seed-sprouting details. You can find germination information in books and online, too. But sources don’t always agree, so if in doubt, get several opinions.
Besides cold treatment, there’s the question of how deep to plant each kind of seed. Some seeds require light to sprout; sow these seeds on top of the soil. Among seeds to sow on the surface are alumroot, Helen’s flower, lobelia, wild mint, and penstemon. Barely cover milkweed and wild ginger seeds. As for baptisia, you can skip the stratification but soak the seeds in warm water for 24 hours and then chip each seed with a sharp knife before planting ¼-inch deep.
Why bother growing native plants from seeds? It’s economical, yes. It’s also rewarding. And who knows? You may end up with some beautiful plants unlike any others.
