If you grow peonies, August is one of those surprisingly important months that can make or break next spring’s show. A lot of gardeners think peonies are “set it and forget it” plants, but in my experience here in the Midwest, late summer is when I can really help them settle in, build roots, and store up the energy that turns into those huge, dinner-plate blooms we all wait for. I’ve learned this the hard way after babying peonies in May and June, then ignoring them in August when they were actually doing some of their most important underground work.
If your peonies looked a little underwhelming this year, or if you planted new ones recently and want them to get off to a strong start, this is the month to be intentional. Below are the August jobs I prioritize every year, from watering and feeding to cutting back diseased foliage and planning fall planting depth correctly. None of it is complicated, but the details matter more than most people realize.
1. Water deeply, but stop the daily sprinkling
In August, I focus on deep, infrequent watering instead of quick surface watering. Peonies need moisture down where the roots are forming, not just a damp top inch of soil. A good target is about 1 inch of water per week, including rainfall, which works out to roughly 5 gallons per square yard of bed space.
If the weather is brutally hot and dry, especially with several days above 88 to 90 degrees, I’ll check the soil 3 to 4 inches down. If it feels dry at that depth, I water slowly at the base for 20 to 30 minutes with a hose on a light trickle or soaker hose. I avoid overhead watering whenever I can because wet foliage overnight is just asking for fungal trouble.
2. Clear away weeds so roots are not competing for moisture
August weeds are sneaky because they look harmless for a while, then suddenly they are stealing water and nutrients at exactly the wrong time. Around each peony, I keep a weed-free circle at least 18 inches wide, and for larger established plants, closer to 24 inches is even better.
I hand-pull weeds instead of hacking around with a hoe right next to the crown. Peony roots and buds can be closer to the surface than people expect, and I do not like disturbing them. If I’m short on time after work, I’ll spend just 10 minutes per bed with a bucket and gloves, and honestly, that small August habit pays off more than one big cleanup later.
3. Check mulch depth and pull it back from the crown
This is a big one. Peonies hate being smothered, and one of the most common reasons they fail to bloom well is that the crown gets buried too deeply. In August, I check any mulch around the plant and make sure it is no more than 2 inches deep around the root zone and not piled directly over the crown.
I leave a bare ring of about 2 to 3 inches around the center of the plant so air can circulate and the buds are not buried. Shredded bark, composted leaves, or fine wood mulch can all work, but thick mulch right on top of the crown can lead to rot and weak flowering. If you planted in spring and kept adding mulch to hold moisture, now is the time to make sure you did not accidentally create a mound over the plant.
4. Remove diseased or badly spotted foliage, but do not scalp the whole plant early
By August, peony leaves often show some spotting, especially after a humid summer. I look for blackened stems, purple-brown blotches, powdery residue, or leaves that are collapsing from fungal issues like botrytis or leaf blotch. If I see affected leaves, I prune off only the damaged material and throw it in the trash, not the compost pile.
What I do not do is cut the whole plant to the ground just because it looks a little rough. The foliage is still feeding the roots. As long as the majority of the leaves are green enough to photosynthesize, I leave them in place. Full cutback is better saved for fall after a hard frost, unless the plant is heavily diseased and clearly declining.
5. Skip heavy nitrogen and use a light, balanced feeding only if your soil truly needs it
August is not the time to push lots of soft leafy growth. I avoid high-nitrogen lawn fertilizers anywhere near peonies because they can encourage weak top growth instead of stronger root development. If a soil test shows low fertility, or if the plants are in very lean soil, I use a light application of a balanced, low-nitrogen fertilizer such as 5-10-10 or 10-10-10.
For established plants, I keep it modest, usually about 1/4 to 1/2 cup per plant spread in a ring 8 to 12 inches away from the crown, then watered in well. Never dump fertilizer directly on the crown. If you haven’t tested your soil, compost is often the safer route: 1/2 inch of finished compost spread around the drip line gives gentle nutrition without overdoing it.
6. Loosen your calendar for transplanting and dividing at the right moment
August is when I start planning peony moves, even if I wait until late August or September to actually dig. If a peony has been struggling because it is shaded, crowded, or planted in the wrong place, now is the time to decide whether it needs relocation. In most Midwest gardens, late August through September is the sweet spot because soil is still warm enough for root growth, but the worst summer stress is easing.
I mark the plants I want to move with a flag or plant tag now, while I can still see how they performed this year. That saves me from forgetting which clump had weak flowering or which one is getting swallowed by nearby shrubs. If I am dividing, I also start prepping the new hole before I dig anything up, because once a peony root is out of the ground, I want to replant it promptly.
7. Prepare new planting holes wide, deep, and in full sun
If you are adding new peonies this fall, August is an ideal time to prep the site. I choose a location with at least 6 hours of direct sun, though 8 hours is even better for the biggest blooms and strongest stems. Morning sun is especially helpful because it dries dew quickly and reduces disease pressure.
I dig a hole about 18 inches wide and 12 to 18 inches deep, then mix the native soil with a little compost if the soil is poor. I do not make the hole into a soft, overly rich bowl of potting mix, because roots need to transition into the surrounding ground. Good drainage matters more than fancy amendments. If water sits in the planting area for more than a few hours after heavy rain, that spot is not ideal for peonies.
8. Get planting depth exactly right when setting roots
This is probably the single most critical detail for future blooms. Peony eyes, which are the pink or reddish buds on the root, should sit only 1 to 2 inches below the soil surface in cold-winter climates like much of the Midwest. In warmer areas, closer to 1 inch deep is often best. Plant them too deep, and you may get healthy leaves but very few flowers.
Whenever I replant or divide peonies, I actually use my hand or a small ruler to check the depth before backfilling completely. After watering, soil settles, so I check again. I learned this after planting one too deep by maybe just another inch or so and waiting two years for the bloom performance to improve. It finally did after I lifted and reset it shallower.
9. Space plants generously for airflow and long-term growth
It is tempting to tuck peonies close together when the bed looks sparse, but mature plants need room. I aim for 3 to 4 feet between most herbaceous peonies. That spacing improves air circulation, lowers disease risk, and gives each plant enough root territory to establish well.
If you are designing a mixed border, remember that nearby perennials can crowd the crown over time. I keep aggressive spreaders, like some bee balms or fast-growing ornamental grasses, from encroaching into the peony’s zone. What looks roomy in year one can turn into a traffic jam by year three.
10. Keep an eye out for stress from heat, drought, and reflected sun
August can be rough on peonies, especially if they are planted near south-facing walls, driveways, or stone edging that radiates heat. If foliage is scorched at the edges or the plant wilts repeatedly in late afternoon, I look at the microclimate, not just the watering schedule.
Sometimes the fix is simple. A 2-inch mulch layer over the root zone, proper deep watering, and removing heat-trapping weeds can be enough. In a really exposed spot, I have even used temporary shade cloth during an extreme heat wave, especially for a newly planted division. Not forever, just for a week of 95-degree stress so the plant can settle without being cooked.
11. Do not let seed production drain the plant’s energy
If your peonies formed seed heads after flowering and you never deadheaded them, August is a fine time to remove those spent heads if they are still attached. Seed production takes energy that could otherwise support root and bud development. I snip the stem back to a strong leaf, using clean pruners.
This is not a massive rescue move if you missed deadheading earlier, but it is still worth doing. On a busy weeknight, this is one of those quick garden tasks I can squeeze in before dinner, and it makes the plants look tidier too.
12. Inspect for ants, aphids, and other pests without overreacting
People still worry about ants on peonies, so I always like to mention this: ants are usually harmless on peony buds and do not damage the flowers. In August, I am more concerned with checking the stems and undersides of leaves for aphids, thrips, or signs of stress that make the plant vulnerable.
If I find a small aphid population, I usually blast it off with water or wipe stems by hand. I save insecticidal soap for heavier infestations, and I use it early or late in the day when temperatures are below about 85 degrees to avoid leaf burn. Most healthy, established peonies can handle light pest pressure without much trouble.
13. Mark weak performers now so you can troubleshoot bloom problems later
August is when I walk the garden with a notebook or my phone and make notes about which peonies bloomed heavily, which flopped, and which barely flowered. It sounds a little nerdy, but it helps so much. If a plant got less than 4 to 5 hours of sun because a nearby tree filled in, I write that down. If another one stayed wet after storms, I note that too.
By next spring, it is easy to forget what happened this season. A simple note like “2 blooms only, shaded by maple after 2 p.m.” can tell you exactly why a peony needs moving. Good bloom troubleshooting almost always starts with observations made in late summer, not guesses made in April.
14. Plan your fall cleanup now to prevent disease carryover
Even though the full cleanup comes later, August is a smart time to get ready. If your peonies had fungal issues this year, make a plan to cut stems down to 1 to 2 inches after a hard frost and remove every bit of fallen debris. Diseased foliage left in the bed can reinfect plants the next season.
I also sanitize pruners with rubbing alcohol or a disinfecting wipe between plants if disease is present. It takes maybe 30 seconds, and it is one of those little chores that helps more than people think. Healthy peony roots going into winter plus a clean bed going into spring is the combination that gives me the most reliable bloom flush.
15. Be patient with first-year and recently divided peonies
This might be the hardest August task of all: doing the right work, then waiting. Freshly planted or divided peonies often spend their first season focusing more on roots than flowers. That does not mean you failed. In fact, if the plant is watered properly, set at the correct depth, and kept healthy through August, it is doing exactly what it should.
I always remind myself that peonies are a long-game plant. Some divisions give a respectable bloom the very next spring, while others take 2 to 3 years to really settle in and perform. But once they do, they can reward you for decades. That’s why I never mind giving them a little extra attention in August. It’s one of the highest-return garden jobs I do all year.