If you have yet to annihilate your peonies, make this a priority as soon as possible. All peonies should be pruned to the ground in early October to prevent the spread of more disease problems over the late fall. Let us explain why!In late summer, diseases run rampant on flowering shrubs. Peonies seem to attract a host of unusual diseases, among them botrytis (bud rot), stem rot (sclerotinia), leaf blotch and anthracnose. Some diseases develop in early-to-mid summer, and simply carry on into the fall. Of all diseases, botrytis is considered the worst. Gardeners who leave peonies intact in the fall always encounter botrytis problems the following spring. Flower buds turn black, never opening. In a matter of weeks, buds fall from the shrub.
Don’t let botrytis ruin your peony flowers next June. With a sharp pruning shears, prune all peony stalks to the ground. When you are finished, there should be no evidence whatever that a peony stood in place just minutes before. Cut every stalk/cane to the ground, then spend a few moments ridding the soil of debris and litter.
Finally, set the stage for peony flowering next June. Around the border where you have pruned stalks to the ground, make a liberal application of ground limestone to sweeten the soil. Peony needs a soil pH around 7 or a little higher to extract plant minerals from the soil. If you have an electronic pH soil tester, by all means check the soil pH on two or more sides of the plant. A sugar coating of lime is always a good practice. Follow this with a shovel or two of composted cow manure spread atop the soil where you have limed. Finally, scratch the lime and cow manure inyo the top inch of soil. That’s it!
Remember, peonies are never mulched for the winter. The soil should be bare when you have completed your preparatory work for next year’s flowering. You needn’t worry about botrytis disease attacking peonies early next spring because, before the first pink-red shoots exit the soil, you will scatter a thin layer of sharp sand atop the soil. In effect, you will be “burying disease spores” next March-April when you apply sharp sand. Other less-informed gardeners will have to spray Bordeaux Mixture to the shoots when they exit the soil, but you can take it easy and let the shoots happen as they will. After all, the sand does the job!
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