It’s peony season here in Minnesota, which usually means an abundance of blooms and a few peony problems. Peonies are a heritage plant in our part of the world and typically bloom for a couple of weeks in early summer. We have several peony breeders in the state and some hold open days during this time of the year.
On the whole, they are one of the easiest, most care-free and long-lived plants in the garden, but there can be a few peony problems. This year, the heat is a small issue. We’ve set heat records this week, and that means the plants will bloom and fade quickly. Like a lot of other gardeners, I’ve been running around snipping buds just before they bloom to bring them into the house. They last a bit longer in the vase and I can enjoy their scent while hiding from the heat.
Here are four more common peony problems and what to do about them.
Easily the most common peony problem is that they flop over. Peony blooms are large compared to their stems. Add some rain or a windy day and they end up bloomside down on the ground. Installing plant supports early in the season is the best way to prevent flopping. I’ve used a variety of supports both half-circle supports and full circle supports, and the full-circle supports work best for peonies. Get metal rather than plastic, if you can afford it, and look carefully at the size of the support before buying. Some gardeners use modified tomato cages as supports, too.
Whichever support you choose, get it on the plant early—preferably before or just as shoots emerge in spring. Even with a support, you may have a bloom or two flop over. Just pick it and bring it into the house.
You can also choose varieties of peonies that have been bred to have stronger stems. Many of these are Itoh peonies, which are a cross between tree peonies and herbaceous peonies. The heritage peonies that I love are floppers, so support is mandatory.
I’m facing a case of powdery mildew on one of my peonies this year. Powdery mildew is a fungal condition that flourishes when plants are in damp or stressful conditions. It has not been a wet year, but this particular peony is planted next to a garage wall and very close to a small tree and other peony. The conditions are not ideal as peonies do best with plenty of sun and lots of air flow around them.
There are a variety of sprays and concoctions you can try to reduce powdery mildew—most contain a horticultural oil, such as neem oil. However, the University of Minnesota and many other experts recommend just tolerating powdery mildew during the growing season. At the end of the season, you should be sure to remove all the infected leaves from the area. Given how bad my powdery mildew is, I plan to prune out some of the peony stems after blooming to give the plant more airflow. In the fall, I’ll collect all the leaves and stems and put them in the trash.
Should I move my Duchesse de Nemours peony? That’s an option, but it should not be done until September. I have a few sunnier, more open spots in my front garden that would look great with a peony in them. Moving the peony might bring on the next peony problem, however.
Every now and then, a peony will not bloom. There are lots of reasons peonies don’t bloom and most of them are of short duration. For instance, if I move the powdery mildew peony, it might not bloom next summer. Peonies last up to 100 years, but it takes them awhile to get accustomed to a new location. Other reasons peonies might not bloom are that they were planted improperly (usually too deeply), over-fertilized, or planted in a place with too little sun. If your peony was planted in the past couple of years, don’t worry too much about the lack of bloom. After that, however, you may want to consider other reasons why it might be not be flowering.
Another common peony problem is botrytis blight. It’s also called gray mold and is another fungal disease that occurs most often during wet growing seasons. It can be devastating, causing stalks to rot and buds to fall off. Initially, the disease looks almost like your peony has blackspot, which circular reddish brown spots on the leaves. Buds will be brown and crusty.
Like powdery mildew, cleaning up the foliage in the fall and disposing of it is one step to prevent the disease from taking hold. Encouraging drainage and air circulation and planting peonies in sunny conditions also helps. Do not compost diseased foliage to prevent further spread of the disease.
These are not the only problems with peonies but are the most common. Overall, peonies are easy care, long lasting and beautiful. Every northern garden should have at least one.