Risks of removing leaves to peonies*



I read your reply to “white powder on peonies”.
To treat a similar mildew, I took the option of snipping leaves instead of using a chemical. However, by the time i was finished, most of the foliage was gone. Then I remember reading a previous suggestion which stated that the foliage wasn’t supposed to be removed until Fall. I noticed that the roses are responding to composting and watering, so maybe I panicked, not wishing to see the disease spread. Hindsight made me realize the disease has been there for years, and it hasn’t spread to the roses.
These plants have lots of sun, and space. However, I noticed that the soaker hose runs through the middle of one group of stems, meaning peonies get wet feet. I’ve applied compost (Promix sheep manure), but perhaps too late in the season. I haven’t used fertilizer.
I have a second Peonie group with a similar condition which I haven’t cut away. I could try to use a chemical with that one.
What is a risk to removing most of the foliage to the first plant? Can I do anything that could protect the plant, such as wrap it in something, such as the winter bushes I see protected?


As noted in the TMG gardener reply which you have already reviewed, the powdery mildew infecting your peonies should not cause permanent damage to your plants, although it can be unsightly and disfiguring during a particular growing season.

If you want to curb the infection this year you can treat the peonies with horticultural oil although its effectiveness is a bit inconclusive.
In order to prevent an outbreak in future years I suggest moving the soaker hose which runs though your peonies as it can cause the moist environment which some of the pathogens causing powdery mildew need to develop. Providing adequate air circulation, sufficient light and avoiding crowding are very important, and you seem to be doing all of that already.

While it advisable to wait until fall to remove the infected leaves, removing them early should not prove fatal, although removing the leaves means that the plants will not have as much green growth to photosynthesize and use to create/store nutrients for the winter.  
Although you have not indicated whether you have tree peonies or herbaceous peonies, I assume because you are growing them in groups that they are herbaceous.  The infected plants should be cut to the ground in the fall and the debris removed.  There is no need to wrap the plants (indeed after they have been cut back there be nothing to wrap and wrapping them would likely decrease the air circulation thereby creating a more favourable environment for the development of powdery mildew).

As noted in the previous response next year you can consider applying preventative fungicide.
It sounds like you are doing the right things.  Good luck!