My friend has an Echinacea that is forming hard domed seedheads but no petals. It is not new and this is the first time she has experienced this. What is causing it? What can she do to cure the problem?
I bet anything it's eriophyid mites. I have had good luck with Bayer Granules for Roses. It's the systemic kind. It goes through the roots and kills them. I would pull all of the effected blooms off and trash them in something away from your garden. It's possible they could bloom normally next Spring or this fall if you treat them now.