A. Powdery mildew is a fungus that over winters on plant debris or buds of ornamental and woody perennials and spreads by wind in spring. But sprays are more preventive than corrective. You have to treat plants before they show any symptoms and keep spraying. A. Dividing perennials, bulbs and some shrubs is a way to get more plants and is often necessary to keep plants healthy. Fall is the best time to divide perennials that bloom in spring and early summer.
Early spring is the best time to divide perennials that bloom in late summer and autumn.
The numbers are the NPK percentages. A. Fall is a great time to plant trees, shrubs, perennials, grasses, spring-blooming bulbs and even seeds of many annuals. In fall, the soil is warm and roots can take hold before cold weather comes. Plus, in the fall, plants will put energy into establishing roots instead of leaves and flowers. A. Late October or early November is usually a good time to cut them back to the crown.