Every August, my peonies start looking a little tired, and I know I’m standing at one of the most important turning points for next spring’s flowers. It’s tempting to ignore them once the big spring show is over, especially when tomatoes are coming in, school schedules are shifting, and the whole garden feels a little shaggy. But I’ve learned the hard way that what I do with my peonies in late summer has a huge effect on how strong the plants are, how healthy the roots stay through winter, and how many blooms I get when spring rolls back around.
If you’ve got peonies and you want bigger, fuller flowers next year, August is not the month to coast. It’s the month to clean up disease, protect foliage that is still feeding the roots, water deeply, and make smart decisions about cutting back instead of just hacking everything to the ground too early. I’m going to walk you through the steps I take in my own Midwest garden every August, including when to trim, what to remove, what to leave alone, and how to set your plants up for massive blooms next spring.
1. Inspect every peony plant for fungal disease before you cut anything
Before I touch my pruners, I do a full inspection plant by plant. In August, peony foliage often shows signs of botrytis blight, leaf blotch, blackened stems, or spotting that started earlier in the season. I look for brown or black patches on leaves, fuzzy gray mold on damaged tissue, shriveled stems, and any foliage that looks collapsed instead of naturally aging.
This step matters because you do not want to spread disease from one plant to another with dirty tools or leave infected material sitting around the crown. If more than 25 to 30 percent of a stem looks diseased, I mark it for removal. If the foliage is mostly green and healthy, I leave it alone for now so it can keep feeding the roots. A quick 5-minute inspection per clump can save you a lot of trouble next spring.
2. Do not cut the whole plant to the ground too early
This is the biggest mistake I see, and honestly, I made it myself when I first started gardening. Peonies are building energy in their leaves after flowering. Those leaves are basically little solar panels, helping the roots store reserves for next year’s shoots and blooms. If you shear the whole plant down in August just because it looks messy, you reduce the plant’s ability to recharge.
As a general rule, I only remove clearly damaged, diseased, or fully dead foliage in August. I save the full cutback for fall, usually after a hard frost when the foliage has yellowed or collapsed naturally. If your peonies are still mostly green, let them keep working. Think of August as cleanup and management, not total shutdown.
3. Remove spent flower stems and any weak, flopping growth the right way
If you still have old flower stems hanging around, now is a great time to tidy them. I trace each spent bloom stem down to a strong leaf junction and make a clean cut there, rather than leaving a long, dry stick poking out of the plant. This keeps the clump neater and reduces places where disease can linger.
For weak or flopping stems, especially those lying on wet mulch or crowded into the center, I thin selectively. I never remove more than about one-third of the total foliage at this stage unless disease is severe. A good pair of bypass pruners makes a cleaner cut than old scissors, and I disinfect the blades between plants with 70 percent isopropyl alcohol or a disinfecting wipe.
4. Cut out diseased foliage immediately and bag it
If you find leaves with black spots, blotches, mold, or obvious rot, go ahead and remove them in August. This is the urgent part of late-summer peony care. I cut infected stems down as low as I can without damaging the crown, especially if the infection runs down the stalk.
One thing I’m strict about: I never compost diseased peony material. It goes straight into a yard waste bag or the trash, depending on local rules. Fallen peony leaves around the base get cleaned up too. Disease spores can overwinter in debris, and the extra 10 minutes of cleanup now is absolutely worth it. On humid Midwest evenings, that infected foliage can get worse fast.
5. Water deeply in August so the roots keep developing
Even though the flowers are long gone, August is still a root-building month. Peonies need moisture to keep roots active, especially during hot, dry stretches. If I don’t get at least 1 inch of rain in a week, I water deeply once rather than sprinkling lightly every day.
For established peonies, I aim to moisten the soil 6 to 8 inches deep. In my garden, that usually means about 2 to 3 gallons of water for a medium clump, applied slowly at the base. Newly planted peonies may need more frequent watering, about every 5 to 7 days in dry weather, but I still avoid soggy soil. The goal is evenly moist, not swampy. Dry stress in late summer can mean weaker flower buds and poorer bloom performance next year.
6. Keep mulch light and away from the crown
Peonies hate being buried too deeply, and August is a smart time to check whether mulch has crept up around the crown. I pull mulch back so there is a 2- to 3-inch clear space around the center of the plant. If the mulch layer is thicker than about 2 inches, I thin it.
This is especially important because excess mulch can hold too much moisture against the stems and crown, which encourages rot and fungal issues. In heavy Midwestern clay soil, that extra wetness can really linger. A light layer of shredded bark or leaf mulch is fine around the root zone, but never pile it up like a volcano around the plant.
7. Skip high-nitrogen fertilizer and focus on root support instead
August is not the time to push lots of soft, leafy growth. If you feed peonies with a high-nitrogen lawn-type fertilizer, you can encourage weak top growth instead of helping the plant store energy properly. I avoid anything with a first number that is much higher than the others, like 24-0-8.
If your soil is poor and you want to feed lightly, use a low-nitrogen, balanced or bloom-supporting fertilizer, such as 5-10-10 or 10-10-10, applied sparingly according to label directions. For many established peonies, I don’t fertilize in August at all unless a soil test suggests it. If you do feed, keep it several inches away from the crown and water it in well. More is not better here.
8. Loosen competition from weeds and aggressive neighboring plants
Peonies do not love fighting with thirsty weeds, creeping groundcovers, or overgrown perennials in late summer. I clear a ring at least 12 to 18 inches around each peony clump so the roots are not competing for every bit of water and nutrients.
When I weed near peonies in August, I use my hands or a small hand fork rather than deep chopping with a hoe. Peony eyes and shallow feeder roots can be damaged if you get too aggressive. If another plant, like bee balm, mint, or a floppy coneflower clump, is crowding the peony’s air circulation, I cut that neighbor back or divide it later in the season. Better airflow now means healthier foliage heading into fall.
9. Mark weak-blooming plants for dividing or replanting later
August is a great diagnostic month. If a peony produced tiny blooms, fewer flowers than usual, or lots of foliage and almost no buds, I make a note now while I can still see the plant’s position and size. The issue may be overcrowding, too much shade, poor drainage, or planting depth that is too deep.
I don’t usually divide herbaceous peonies in early August in my area because the heat can be rough, but I absolutely tag problem plants for early fall attention. A simple plant marker or even colored twist tie works. When September arrives, you’ll be glad you remembered which clumps need action. Healthy divisions typically need 3 to 5 eyes and a sturdy root section to re-establish well.
10. Check planting depth if blooms were disappointing
This is one of the most overlooked reasons for poor flowering. In many parts of the Midwest, herbaceous peony eyes should sit only about 1 to 2 inches below the soil surface. If they are planted 3 or 4 inches deep, the plant may grow leaves just fine but refuse to bloom heavily.
August is not always the month to dig and reset them, but it is the perfect month to investigate gently. Brush soil aside near the crown and see where those buds or eyes are sitting. If the plant is clearly too deep, plan to lift and replant it in early fall. I’ve had peonies go from stingy bloomers to absolute stars after correcting depth by just a couple of inches.
11. Sanitize your tools between plants every single time
I know this sounds fussy, but with peonies it really does matter. If one plant has fungal spotting or stem rot and you cut into a healthy plant without cleaning your pruners, you can spread problems quickly. In August, when humidity and disease pressure can still be high, I keep a rag and a small spray bottle of 70 percent alcohol in a bucket while I work.
My routine is simple: cut, wipe blades, spray, wait a few seconds, move to the next plant. It adds maybe 30 seconds between clumps. That tiny habit is a lot easier than dealing with a whole bed of infected peonies next year.
12. Make a plan now for the full fall cutback
August cleanup is not the same as the final seasonal cutback. I think of this month as prep work. Once the foliage is fully yellowed, browned, or knocked down by frost in fall, that is when I cut herbaceous peonies to about 1 to 2 inches above the soil line and remove all debris.
Having a plan now helps you avoid either forgetting the job entirely or doing it too soon. If you garden the way I do, with work deadlines, grocery runs, and soccer practice all crammed into the same week, it helps to put a reminder on your phone for late October or early November, depending on your zone. Strong spring blooms usually start with disciplined fall sanitation, and August is where that discipline begins.
13. Support healthy foliage instead of chasing a tidy look
This is more of a mindset shift, but it has made a real difference in my garden. By August, peonies are not exactly glamorous. They can look a little leggy, a little spotted, and a little overshadowed by everything else. But if the foliage is mostly healthy, it is still valuable. I’ve learned not to sacrifice next spring’s flowers just because I want the bed to look instantly neater this weekend.
If appearance is bothering you, tuck peonies visually behind late-summer annuals in containers, edge the bed cleanly, or use a discreet support ring to keep stems upright. Those tricks preserve the plant’s energy-building foliage without forcing an early cutback. In my experience, patience in August pays off in armfuls of blooms in May.
14. Track what worked so you can get even bigger blooms next year
One thing I started doing a few years ago was keeping a quick garden note on my phone. Nothing fancy, just entries like “south bed peony had black spot by Aug. 12,” “front walkway clump too shaded by hydrangea,” or “deep watered twice during dry spell.” Those notes have helped me connect late-summer care with spring bloom results much better than memory alone.
If one peony gives you 20 stems with huge flowers next spring while another gives you 6 weak blooms, the answer often goes back to conditions you could already see in August. A 2-minute note now can help you adjust watering, spacing, sunlight, or disease control in time to make next year’s display much better.