If you grow peonies, September is one of those make-or-break months that can set you up for an absolutely gorgeous spring or leave you wondering why your plants looked tired, spotty, or stingy with blooms. I’ve learned this the hard way in my Midwest yard, where one week can still feel like summer and the next suddenly smells like fall. Peonies are tough, long-lived plants, but they really do benefit from the right cleanup and cutback routine at the right time.

When I first started gardening, I assumed “cut them back” just meant grabbing the pruners and hacking everything down as soon as the flowers were gone. Not quite. September care is more strategic than that. If you want fuller plants, cleaner foliage, fewer disease problems, and those big lush blooms next spring, there are a handful of steps worth doing now. Here’s exactly what I would focus on this month, in order, including what to cut, what to leave, what to toss, and what not to do.

1. Wait for the right September timing before cutting anything

The first critical step is not rushing. In most Midwest gardens, I wait until peony foliage starts looking yellowed, browned, or clearly worn down by cooler nights before I do a full cutback. Early September may still be too soon if your peonies are green and healthy, because those leaves are still feeding the roots and helping the plant store energy for next year’s flowers.

As a general rule, I start watching closely when nighttime temperatures are regularly dropping into the 40s and low 50s. If the plant still looks vigorous, I leave it alone for another week or two. If the foliage is spotted, collapsing, or frost-nipped, that’s my cue. In warmer parts of the country, this job may slide into late September or even October. The point is to cut back based on plant condition and local weather, not just the calendar.

2. Remove any diseased or badly spotted foliage first

If your peony leaves have black spots, dark blotches, powdery coating, or stems that look streaked and unhealthy, take those off as soon as you notice them. Peonies commonly deal with fungal issues like botrytis and leaf blotch, and infected material should not sit around any longer than necessary.

I keep a yard waste bag or bucket right beside me while I work so diseased leaves never hit the ground. On a mature peony, that might mean removing 20 to 50 damaged stems or leaves before the full cutback happens. This one habit has made a noticeable difference in my own beds, especially in damp years when late summer humidity hangs around forever.

3. Cut herbaceous peonies down to 1 to 2 inches above the soil line

For standard herbaceous peonies, September cutback should be firm and clean. Once the foliage is ready to come down, use sharp pruners and cut each stem to about 1 to 2 inches above the soil. You do not need to leave tall stubs. Shorter is better because it removes hiding places for disease spores and insects.

I usually work in a circle around the clump, gathering stems in one hand and cutting with the other. A mature peony can have dozens of stems, so this takes me about 5 to 10 minutes per plant. If the stems are thick, bypass pruners work better than lightweight snips. Try to make clean cuts instead of tearing or twisting the stems off.

4. Do not cut tree peonies and Itoh peonies the same way

This is where a lot of gardeners get tripped up. Herbaceous peonies die back to the ground and should be cut low. Tree peonies are woody shrubs, and cutting them to the ground would remove next year’s flowering framework. Itoh peonies, which are intersectional hybrids, often die back mostly like herbaceous types but may leave some short woody structure.

If you have a tree peony, only remove dead leaves and obviously dead wood, and wait until spring to assess winter damage more fully. If you have an Itoh peony, remove dead top growth but avoid aggressively carving into any firm woody crown tissue. When I moved into my house, one peony turned out not to be the “regular kind” I thought it was, and I’m still grateful I paused before cutting everything flat.

5. Sanitize your pruners between plants

If you cut one peony with leaf spot or botrytis and then move right to the next without cleaning your tools, you can spread trouble through the bed. I keep a small container of disinfectant wipes or a spray bottle with 70% isopropyl alcohol in my garden tote for exactly this reason.

A quick spray or wipe between plants is usually enough for routine cleanup. If one plant is heavily diseased, I’m extra careful and let the blades stay wet for at least 30 seconds before wiping them dry. It adds maybe 1 extra minute per plant, which is worth it to avoid carrying pathogens around the garden.

6. Bag and remove all peony debris instead of composting it

After cutback, the cleanup is just as important as the pruning. Every leaf, stem, and petal remnant should be raked up and removed from the area. If the plant had any disease at all, do not compost that material at home unless you are absolutely sure your compost pile runs hot enough to destroy fungal spores. Most backyard piles do not consistently hit 130 to 150 degrees Fahrenheit for long enough.

I either bag the debris for municipal yard waste pickup or dispose of it according to local guidelines. Then I do one extra pass with a hand rake or gloved hands to make sure nothing is left tucked around the crown. This step feels a little fussy in the moment, but it pays off in spring when the new shoots come up through much cleaner soil.

7. Check the crown depth and make sure it is not buried too deeply

If your peonies have plenty of foliage but disappointing flowers, planting depth may be part of the problem. Herbaceous peony eyes should usually sit only about 1 to 2 inches below the soil surface in cold-winter climates. Much deeper than that, and you may get leaves without many blooms.

September is a good time to inspect the base of the plant after cleanup. If mulch, compost, or drifting soil has built up over the crown, gently pull some back. I’ve found peonies near downspouts or edging can slowly get buried over a few seasons without me noticing. You don’t need to dig the plant up unless it’s significantly too deep, but you do want the crown area exposed correctly going into fall.

8. Water deeply once a week if September is dry

A lot of people stop thinking about watering once summer flowers fade, but peonies are still building reserves underground in early fall. If your area is dry, give them about 1 inch of water per week, either from rainfall or irrigation. That works out to roughly 0.6 gallons per square foot.

I like to water slowly at the base rather than overhead, especially if foliage is still present. A deep soak every 7 to 10 days is better than a daily sprinkle. In my yard, I stick a finger 2 to 3 inches into the soil; if it feels dry at that depth, I water. Consistent moisture now can help roots stay active until the ground cools more seriously.

9. Skip heavy fertilizer, but top-dress lightly if your soil is poor

September is not the time to push lush top growth with a strong nitrogen fertilizer. That can encourage soft growth at the wrong moment. If your soil is reasonably healthy, I usually leave peonies alone after cleanup and wait until spring for any real feeding plan.

If your soil is lean or you know the bed needs help, a light top-dressing of compost around the plant, not directly over the crown, can be useful. I’m talking about a 1-inch layer spread in a ring 6 to 12 inches away from the center. You can also use a low-nitrogen bulb or perennial fertilizer according to label directions, but go easy. More is not better with peonies.

10. Keep mulch away from the crown

Peonies appreciate winter protection in colder regions, but burying the crown under a thick blanket of mulch is one of the easiest ways to reduce blooming. After cutback, keep mulch pulled back so the crown is not smothered. If you mulch at all, think light and loose, not deep and packed.

For established plants, I often use little to no mulch directly over the crown. If I’m mulching the surrounding bed, I keep it to about 2 inches deep and leave a small open circle around the plant base. Newly planted peonies may need a bit more winter buffering, but even then I’m careful not to mound mulch right on top of the eyes.

11. Mark the plant location before winter sets in

This sounds simple, but it saves so much frustration. Once herbaceous peonies are cut back, they disappear. By November, it is very easy to forget exactly where the crown sits, especially in a crowded perennial bed.

I push in a short plant marker or a 12- to 18-inch bamboo stake a few inches away from the center so I can see the spot all winter and very early spring. That prevents accidental digging, edging, or stepping on the emerging shoots. I learned this after my husband very innocently parked a leaf bag right on top of one of mine one fall, and we both felt terrible when those red spring shoots came up bent.

12. Divide or transplant only if absolutely necessary

Early fall is the best time to divide or move peonies, but I still treat it as a last resort. Peonies hate unnecessary disturbance and may sulk for 1 to 3 years after being moved. If the plant is healthy and blooming well enough, I leave it where it is and simply do the seasonal cleanup.

If you must divide, do it after cutback while soil is still workable. Dig wide, often 12 to 18 inches out from the crown, because peony roots are thick and brittle. Each division should ideally have 3 to 5 eyes and several sturdy roots attached. Replant so the eyes sit no more than 1 to 2 inches below the surface. Water thoroughly after planting, usually with 1 to 2 gallons per division, to settle the soil.

13. Make a quick note now so you can improve bloom size next spring

September is a great time to evaluate the past season honestly. Did the stems flop after a rain? Were the flowers smaller than expected? Did one plant stay in too much shade after nearby shrubs leafed out? I keep a note in my phone with a few observations while the season is still fresh in my mind.

For example, peonies generally bloom best with at least 6 hours of direct sun. If a bed now gets only 4 hours because a young maple has filled in, that could explain weak performance. If blooms were huge but stems collapsed, add a support ring in early spring next year before growth gets tall. These little notes help me actually fix the right problem instead of guessing.

14. Be patient and let winter do its job

After September cleanup, the best thing you can do may be nothing. Peonies need a cold dormancy period to reset well, and once they are cut back, cleaned up, and properly sited, they really are low-maintenance plants. Resist the urge to fuss over them every few weeks.

Some of my best peony years have followed the falls when I simply handled the basics well: proper timing, clean cutback, good sanitation, moderate moisture, and no crown smothering. Massive spring blooms don’t come from one miracle trick. They come from giving the plant a clean, healthy finish to the season so it can store energy and rest properly.

If you tackle these steps this September, you’ll be doing exactly what peonies need most before winter. It’s not complicated, but it is one of those garden chores where small details really matter. And when those fat buds start swelling in spring and the whole plant looks stronger, fuller, and more floriferous, you’ll be so glad you took the extra half hour now.