Q: About 10 years ago I bought five beautiful peony bushes. But for the past three years the buds have “frozen.” Though the plants are full of buds, none ever open. — Janet Grant, Denver, Colo.
A: The buds are being damaged by late frosts. Peony buds are vulnerable to freezing, especially when they are small, about pea size. If they freeze, the buds stay green but stop developing and never bloom. This is not common in your area, so you probably have early-blooming varieties planted in a low-lying area. The coldest air flows into these areas and accumulates on still nights, creating frost pockets. In the fall, transplant the peonies to a warmer spot — either higher ground or someplace where the air can circulate freely. Do this just as the foliage begins to die back. Note how deep the root crown is below the soil surface — typically about 2 inches — and make sure to replant it at the same depth. (Peonies planted too deep often refuse to form any buds at all.) You might also try some very late varieties. Some good ones are ‘Nick Shaylor’ (white), ‘Myra MacRae’ (light pink), and ‘Emma Klehm’ (dark pink). The other possibility is a disease called botrytis, but it usually doesn’t wipe out all the buds, and it typically affects buds when they are larger. Also, if it is botrytis, you should see some blackening on the buds and foliage. To control this disease, cut away and discard all the stems and leaves every fall. In the spring, thin out the stems so that the foliage has more air moving through it.