Q: My peony plants flower for about a week before something causes the flower buds to not open any more. They are showing some browning around the edges.
A: It sounds like a thrips problem. Thrips are tiny insects that chew delicate flower tissue and can cause peonies blooms not to open. Spray the flowers with spinosad (Captain Jack’s Dead Bug Brew) now to kill as many thrips as possible. This may not help with flower opening but it can reduce the number of insects. Next spring consider applying a systemic insecticide when the peony sprouts appear.