Cut your peony down in the fall, right around the time of the first frost. Cutting it back in the middle of summer costs you blooms the following spring.
Here's what's happening while you wait. All summer long, that foliage is soaking up sunshine and sending it down into the roots, building a stronger plant and more blooms for next year. Every week those leaves stay standing is a week of work being done for you.
I'll admit that by the end of summer they can look pretty sad, and I understand the temptation to cut early. Resist it if you can. An easy rule to remember: cut around the first frost. A little earlier is fine, as long as you don't get carried away in July.
Cut all the way down
When it's time, cut the stems all the way to the soil line. Don't leave stubs.
What to do with the foliage
This part matters more than people expect. Once you've cut your peony down, take the foliage and throw it away, send it to landscape recycling, or burn it where local rules allow. Do not compost it.
Peony foliage can carry fungal and mildew spores, and composting it keeps those spores right where you don't want them — in the garden, ready for next spring. Getting the foliage out of your garden is one of the simplest things you can do to prevent disease.
Your patience today gives you healthier blooms next spring. And that's what we all want. Every single bloom we can possibly get.
