Though some of the hybrids are sterile, you can raise coneflowers easily from seed, and if you grow yellow purple coneflower together with the purples, you might even find some hybrids among its seedlings. The seed is ripe when the cone dries out. At this time, the bristles turn dark brown and rather sharp and spiny.
The silvery gray seeds are packed in among the bristles and both fall out when you shatter the cone. I don’t bother separating the seed from the bristles. The seed germinates after 6-12 weeks of cold, moist temperatures.
Sow seeds outdoors or in pots in late fall (cover them lightly). Alternatively, you can soak the seeds in a cup of water for a few hours, and then towel them lightly dry before putting them in a sealed baggie in the refrigerator for the requisite number of weeks. After their chilling, sow the seeds indoors or outside after the danger of frost is passed. They should sprout in 2 weeks.
In the nursery, coneflowers mature rapidly and often flower the first summer from seed germination in the spring. Transplant your plants into well-drained but moist topsoil where they will receive at least 5 hours of summer sun.
For more information on choosing and growing coneflowers, see: http://www.gardensmart.com/?p=articles&title=Coneflowers_Choosing_and_Growing