For best success, plant in late fall for seedling emergence in spring.
Most of these plants have seeds that require a winter of chilling
in order to germinate. Prepare a seedbed that is firm but not
compacted, and that is as free of annual weed seeds as possible.
These seedlings cannot compete with weeds. Cover the seeds with a
shallow layer of soil and firm the soil over them, or rake them in
lightly. Do not plant too deeply. A covering two or three times the
diameter of the seed is about right. After emergence in spring, the
seedlings will grow quite rapidly and will become recognizable in a
few weeks. Most of the perennials will begin flowering in their
second growing season, but a few may flower the first year.
Once they begin producing seeds, many will seed themselves freely.
Clipping the seed stalks when green will prevent self-seeding,
if that is undesirable.
StratificationIn order to plant most wildflower seeds anytime other than late fall, they will need "stratification." Place the seeds on a damp paper towel in a plastic bag and refrigerate for 4 to 12 weeks. Check them periodically until they begin sprouting, then plant carefully.
ScarificationSome seeds have hard coverings and will not take up water for germination. They require "scarification." Large seeds can be nicked with a razor blade or rubbed lightly with fine sandpaper. Small seeds can be soaked in hot water over night. After the seeds swell, plant them immediately without drying.