Prevalent peony pathogens
Q. My peonies look terrible. What’s wrong with them? Should I cut them back now? Will they still bloom next year?
Delores from Poland, Patty from Salem (and three more!)
A. This has been a crazy year with lots of moisture and lots of humidity. Thus, fungal pathogens are attaching our plants from every possible direction.
In general peonies are vigorous plants. They emerge quickly and give beautiful blooms by the last day of May. But most of us don’t have them planted in the proper place for a year like this. They require good drainage, adequate air movement — and full sun. Yes, peonies can survive in partial sun, but they don’t like it. Unfortunately, even some of the ones in full sun are showing signs of distress this year.
There are two prevalent fungal diseases this year (and probably a few more):
Peony leaf blotch — large, ugly blotches that start out red and turn purple, then brown. The leaves really get hammered with this disease and look terrible.
Powdery mildew — plants that look like they have been sprinkled with baby powder. It covers the entire leaf surface in most cases.
So, what can you do? In a year like this, thin the canopy to increase air movement. Use a sharp pair of pruners. Sanitize them when finished and before going to the next plant. Destroy the plant material you remove.
There are fungicides you can use. See this Penn State Extension fact sheet: http://go.osu.edu/sickpeony for a list and instructions. Read the label and follow all directions. But it may be too late and probably not your best option.
Cut the plants back to the ground (and maybe 1” below the soil surface) sometime in the middle of September. Again, destroy the plant material you remove. Consider moving the plants. Dig a hole about 18-24” across and be sure the red colored buds on the roots are about 2 inches below the soil. If the canopy is thick, divide them.
Eric Barrett is the Ohio State University Extension Educator for Agriculture and Natural Resources in Mahoning County. Call the hotline at the office on Mondays at Thursdays from 9am to Noon to submit your questions at 330-533-5538.