Peonies are a favorite in many gardens, and they certainly are in mine.
With their stunning, full blooms and beautiful foliage, peonies add elegance and charm to any landscape.
But as the summer ends and the growing season winds down, it’s important to give them the care they need to thrive next year.
One of the key tasks for maintaining healthy peonies is pruning them in September.
Through years of trial and error, I’ve learned that timing and technique are everything when it comes to pruning peonies.
If you do it right, you’ll set your plants up for a strong growing season next year.
Let’s walk through how to prune peonies in September, with a few personal insights and tips that I’ve picked up along the way.
Why Prune Peonies in September?
September is the perfect time to prune peonies because it falls just after they’ve finished their growing season and are beginning to prepare for dormancy.
By now, the lush green foliage is starting to yellow and fade, signaling that the plant is done gathering energy from the sun.
Pruning during this time helps the peony conserve energy and stay healthy through the winter.
In my experience, waiting until this stage—after the leaves have started to decline but before the first frost—gives the plant plenty of time to store nutrients for next spring.
Pruning peonies in September also helps prevent the spread of disease.
Peonies can be susceptible to fungal issues like botrytis, which can overwinter on dead foliage if it’s left on the ground.
By cutting back the foliage in the fall, you’re removing any potential harbor for these diseases, ensuring that your peonies stay healthy when they reemerge in the spring.
Gather the Right Tools
Before you start pruning, it’s important to have the right tools on hand.
I’ve found that having sharp, clean pruning shears is essential for making clean cuts that won’t damage the plant.
If your shears are dull, you risk tearing or crushing the stems, which can leave your peonies vulnerable to disease.
I also recommend wearing a good pair of gardening gloves.
Peonies are generally easy to prune, but the dead foliage can be a bit messy, and gloves will help protect your hands from any rough or brittle stems.
I like to keep a small bucket or garden bag nearby to collect the cut foliage as I go—this keeps the work area tidy and prevents any disease or pests from lingering in the garden.
Cut Back the Foliage
The main task when pruning peonies in September is cutting back the foliage.
By this time, the leaves will likely have started to turn yellow or brown, which is a sign that they are no longer photosynthesizing and contributing to the plant’s energy reserves.
In my garden, I usually wait until at least 50% of the foliage has turned before I start pruning—this ensures the plant has had enough time to store up energy for the winter.
Using your pruning shears, cut back all of the foliage to about 2-3 inches above the ground.
Make sure to make clean, angled cuts just above a healthy bud or leaf node.
This helps prevent water from pooling on the cut stems, which can lead to rot or disease.
While it might seem a bit drastic to cut the entire plant down to just a few inches, I promise it’s for the best.
In my experience, leaving too much foliage behind can create a habitat for pests and diseases over the winter.
It can feel a little harsh at first, but come spring, your peonies will emerge healthier and more vigorous.
Clean Up the Area
After you’ve finished cutting back the foliage, it’s important to clean up the area around your peonies.
I always make a point to collect every last bit of foliage and dispose of it properly—never leave it to decompose in the garden.
Old peony leaves can harbor diseases like botrytis blight, which can infect the plant again next year if it’s left to overwinter.
If you’ve dealt with fungal issues on your peonies in the past, it’s especially important to be thorough during this cleanup process.
I often give the area a light rake to make sure no dead leaves are hiding among the mulch or soil.
This simple step can make a big difference in preventing disease outbreaks the following season.
In addition to cleaning up the foliage, I also like to inspect the base of the plant for any weeds or debris that may have accumulated over the summer.
Keeping the area around the crown of the plant clear helps ensure good airflow and reduces the risk of fungal diseases.
Mulch for Winter Protection
Once you’ve pruned your peonies and cleaned up the area, it’s time to add a layer of mulch to protect the plant through the winter.
While peonies are hardy and can handle cold temperatures, a layer of mulch helps insulate the roots and keep the soil temperature consistent.
In my garden, I like to use an organic mulch like straw, shredded leaves, or compost, which not only protects the plant but also adds nutrients to the soil as it breaks down.
I usually apply a 2-3 inch layer of mulch around the base of the plant, taking care not to cover the crown.
Mulching too close to the crown can trap moisture and lead to rot, so it’s best to leave a little space around the base of the stems.
This mulch will help protect the roots from extreme temperature fluctuations and keep the soil from freezing and thawing too quickly, which can damage the plant.
Avoid Fertilizing After Pruning
One mistake I’ve seen gardeners make is fertilizing their peonies after pruning.
While it might seem like a good idea to give the plant a boost before winter, fertilizing at this stage can actually do more harm than good.
After pruning, the plant is preparing for dormancy, and adding fertilizer can encourage new growth that won’t have time to harden off before the first frost.
I’ve found that the best time to fertilize peonies is in the early spring, just as they’re starting to break dormancy.
At that point, the plant will be ready to take up nutrients and put them to use as it grows.
If you want to give your peonies a little boost before winter, I recommend using an organic mulch or compost, which will slowly release nutrients into the soil over time without encouraging unnecessary new growth.
Divide Peonies if Needed
If your peonies are starting to look a bit crowded or they’re producing fewer blooms than usual, September can be a good time to divide them.
Peonies don’t need to be divided often, but every 10-15 years or so, you may notice that your plants are becoming too large for their space or that they’re not blooming as vigorously as they used to.
I’ve divided peonies in the fall a few times, and while it’s a bit of a task, it’s worth the effort to rejuvenate the plant.
To divide peonies, carefully dig up the root ball, taking care not to damage the roots.
Once the plant is out of the ground, use a sharp knife or spade to divide the root ball into smaller sections, making sure each division has at least three to five healthy buds.
Replant the divisions at the same depth as the original plant, and water them well.
While dividing peonies can be a bit of work, it’s a great way to encourage more blooms and keep the plant healthy for years to come.
I’ve also found it to be a nice way to share plants with friends and neighbors—peonies make wonderful gifts!
Monitor for Diseases and Pests
After pruning, it’s important to keep an eye on your peonies for any signs of disease or pests.
While pruning in September helps remove much of the old, diseased foliage, it’s still possible for pests or fungal spores to linger in the soil or mulch.
I’ve had issues with botrytis blight in the past, so I’m always on the lookout for symptoms like blackened stems or moldy patches on the remaining foliage.
If you notice any signs of disease after pruning, it’s important to act quickly.
Remove and destroy any affected plant material, and consider applying a fungicide if the problem persists.
In some cases, it may also be helpful to thin out nearby plants to improve airflow around the peonies—this can reduce the humidity that encourages fungal growth.
When it comes to pests, I’ve occasionally had problems with aphids or ants on my peonies.
If you notice these pests, a strong spray of water can usually knock them off, or you can use insecticidal soap for more persistent infestations.
Keeping your garden clean and free of debris also helps reduce the likelihood of pests taking up residence.
Be Patient with Transplanted Peonies
If you’ve decided to divide or transplant your peonies in September, it’s important to be patient.
Peonies are known for being a bit slow to establish themselves after being moved, and it can take a year or two for them to return to full bloom.
In my experience, newly transplanted peonies may not bloom at all the first year, but don’t be discouraged.
As long as the plant is healthy and you’ve planted it at the right depth, it will eventually settle in and produce beautiful blooms.
Just be sure to water it regularly and keep an eye on the soil moisture during the first few weeks after transplanting to help the plant establish strong roots.
Final Thoughts
Pruning peonies in September is an essential part of maintaining their health and ensuring they bloom beautifully year after year.
By cutting back the foliage at the right time, cleaning up the garden area, and adding a protective layer of mulch, you’re setting your peonies up for success through the winter and into the next growing season.
In my years of gardening, I’ve found that peonies are remarkably resilient plants when given the right care.
With a little attention in the fall, you’ll be rewarded with vibrant, fragrant blooms come spring.
Just remember to be patient, keep your pruning tools sharp, and take the time to clean up after you’re done—the results are well worth the effort.
Happy pruning!