Cooler days signal the first signs autumn will be here before we know it. If your peonies have seen better days, there are several tasks you can be doing now to ensure bountiful blooms next spring.
To many people, a bouquet of peony blooms signals spring has arrived. If your peonies have seen better years and haven’t bloomed well, September is one of the best times to move or divide them. It will take about three years for a newly divided and replanted peony to get back to a good size to have a wonderful flower display. If clumps are blooming well, avoid dividing or moving unless it is necessary.
There are a few rules to follow when dividing peonies to ensure success. It is best to divide peonies after they have gone dormant for the year. Let the foliage be your guide on the dormancy of the plant. After it has begun to change color from a healthy green color to a yellowish color, the foliage can be cut back near ground level. Cautiously dig around and under the plants, taking care not to break off the roots. After the plants have been dug around, carefully lift from the ground and wash off the soil. Use a sharp knife to cut the roots, make sure that they have between 3-5 buds and a good portion of fleshy roots. When replanting, make sure the buds are no deeper than 1-2” below the ground level. If they are planted too deep, the peonies won’t bloom.
If your peonies suffered from one of several diseases this summer, now is a great time to take care of those issues too. Powdery mildew is a fungal infection that causes the leaves to have a white to grayish cast to them. High relative humidity and poor air circulation are the main causes for diseases in otherwise healthy peony plants. If the infection is great enough, it can compromise the photosynthesis of the plant leaves and make it hard for the plant to make food, which can lead to a decreased flower show the following year. If your peonies had powdery mildew this past year, you want to make sure that when they go dormant this fall, you clean up and discard any of the infected leaves. Also look at the location of the plants. If possible, try to increase the air circulation in that area to help avoid infection next year.
If your peony buds were more black and shriveled than beautiful, then botrytis might be the culprit. This is another fungal infection that we commonly see during prolonged wet springs. Just like with the powdery mildew, you want to practice good fall clean up and sanitation practices to rid the area of the infected plant material and hope for better weather next year.
At this time of the year, there are also some tasks in the landscape that should be avoided. Avoid pruning and fertilizing roses, trees, and other woody plants now. These practices will promote new growth that won’t have the opportunity to harden off before winter and could increase the risk of winter injury. Other disadvantages to pruning now include the removal of growth that can assist the plant in storing food in the roots and trunk as well as an increase in decay and rot in pruning wounds made in the fall. The best time to prune deciduous trees and shrubs is when they are dormant, preferably in early spring before they leaf out. The best time to prune spring blooming shrubs, like lilac, is after they bloom next spring.
With a little work now, you can ensure plentiful peony blooms next year.
Elizabeth Killinger is the Horticulture Extension Educator with Nebraska Extension in Hall County. For more information contact Elizabeth at firstname.lastname@example.org, her blog at https://huskerhort.com/, or HuskerHort on Facebook and Twitter.