29/07/2026
Do your peonies have a gray cast to them instead of shiny green leaves? You're not alone! In Iowa, the warm, humid days have led to a lot of powdery mildew to form on the leaves, even earlier in the season than normal. It looks bad, that's for sure, but it's not really going to hurt the plant long term.
What can you do? I always encourage clients to leave the leaves for as long as they can stand it. Peonies don't grow new leaves this time of year, so if you cut them back like you do in the fall, they won't have any more leaves to photosynthesize and feed the plant for next year. Even though there is a lot of fungal action, there is still some green on the leaves too, doing the work. Whenever you do cut them back, be sure to discard the leaves. Do not compost or leave them lying on the ground.
A couple preventative measures for the future- make sure they aren't crowded by other plants, giving them some space for air to circulate. Also, make sure your peonies are in full sun (6+ hrs of direct sun). the ones in the shade are more prone to PM and don't bloom as well anyway. If you need to move them, August to September is a good time to do that. You can try to keep PM at bay with a baking soda or potassium bicarbonate spray as soon as you see the first spots, but oftentimes, the whole plant just turns gray, seemingly overnight! Just remember, while it looks bad, it's not going to kill it.
