It’s well known that fall is an excellent time for planting most trees and shrubs. Did you know that it can be a good season for planting, transplanting or dividing perennials, too? The soil is warm, promoting good root establishment, the air temperature is usually more consistent and moderate than it can be in spring or summer, and rainfall is often more consistent. Here are tips for helping perennials get off to a good start in the garden in fall:
- Aim to plant perennials about four to six weeks before your typical first frost date. This leaves them ample time to send out new roots. If you must plant them closer to the frost date, consider planting them slightly deeper than you normally would, to help anchor them against potential frost heaves in winter.
- Concentrate on spring- and summer-flowering perennials when planting in fall; these may establish better than fall bloomers at this time of year, and they’ll likely reward you with a great bloom next year.
- If you plant fall bloomers, consider removing their flowers at planting time to encourage them to put energy into taking root, rather than blooming or making seeds.
- If you're dividing perennials and replanting the divisions, work with spring and early-summer bloomers. Perennials are generally best divided in the season opposite of that in which they bloom (fall for spring and early-summer bloomers; spring for late-summer and fall bloomers).
- Apply a light mulch after planting perennials in fall to conserve moisture. Once the ground freezes, come back and spread another layer of a winter mulch, which will help moderate the soil temperature over the winter, preventing frost heaves that could push your new plants out of the soil.
- If fall rains are scarce, regularly water your newly planted perennials by hand, aiming for an inch of water each week. Water deeply and infrequently, just like with newly planted shrubs.