I never grew them intentionally, but they spontaneously occurred on my acreage in Oklahoma. I would recommend fall/winter sowing.

Looking at the Prairie Moon website, it says this Gention needs 90 days of cold weather to germinate, which is in agreement with debarron's statement. So I would winter sow it.

I think I'll try sowing in a flat and leave in a sheltered place outdoors. Thanks

If you are going to winter sow them in one of those black plastic germination trays with the domes, be watchful in the spring when the temps rise that the black plastic will heat up from the sun, and unless you take precautions to ensure good ventilation your seedlings can cook in their tray. It's happened to me more than once, and some very pricey seeds were squandered.