The best time to plant herbaceous peonies (the ones whose tops die down in the fall) is mid-September. The best time to plant tree peonies is late October and November. Tree peonies also can be planted in the spring.

The best time to divide and transplant peonies is never, unless it is absolutely necessary. If they are blooming well, leave them alone. There are records of peonies that had not been thinned or moved for 50 years and still bloomed beautifully.

If your peonies are not blooming satisfactorily and it appears they are too crowded or have too much competition from tree or shrub roots, dig, divide and replant them in early October. Don't fail to divide them, otherwise they may not bloom again for years.

Peonies need well-drained soil. They need full sun. They will grow in places where they get shade two or three hours a day, but the flowers are not as good as they could be.

Prepare the soil 18 inches deep ahead of time so that it can settle before planting. Be sure not to plant the tubers with the eye more than two inches deep in the soil. Otherwise, they may not bloom for years.

Powdery mildew, a fungus disease, is a serious problem in many gardens at this time of the year. It is fairly easy to recognize. White, powdery blotches appear on leaves, stems and flower buds.

Leaves infected with mildew turn yellow and drop prematurely. Flower buds may fail to open and if they do they are usually deformed. Perennials may be damaged to the point they are more susceptible to winter injury.

Plants most likely to be infected include roses, azaleas, zinnias, phlox, chrysanthemums, dahlias, delphiniums, lilac, crape myrtle and English ivy. In fact, most kinds of ornamentals may be susceptible to one or more of the several strains of powdery mildew.

For mildew on roses, zinnias, chrysanthemums and crape myrtle, specialists recommend spraying with Benlate or Actidione PM. In all cases, directions on the label should be followed closely. For mildew on Azaleas, dahlias, lilacs, phlox, delphiniums, English ivy and photinia, spray with Benlate.

Be sure to spray the underside of the leaf as well as the top.

Beech, birch, catalpa, chinaberry, chestnut, elm, hawthorn, hickory, oaks, sycamores and other trees may become infected with powdery mildew, but this disease on trees is seldom serious enough to justify control measures.

A single treatment cannot be counted on to provide control for a long period of time.