The "prickles" are the seeds. Hope you didn't just throw them on the ground. You'll have tons of coneflowers if you did.

~~Mimi

If you are talking about echinacea (rather than rudbeckia or ratibida) the white "dandruff" between the brown sharp points is the seed. They are white triangles. It's a very common mistake and one I made as a new seed gatherer. Do you need seed? At this time of year, the birds have harvested all of it, so you might have nothing.