Pruning also keeps plants tidy and prevent unwanted reseeding. When flowers dry, curl or turn brown or their colors start to fade, it’s time to deadhead. At the end of the growing season, it helps to do a simple pruning and cleanup to prepare your perennials for winter dormancy and to keep insects from over-wintering in the dried plant material. In late autumn, leave some of the foliage, seed heads and berries for the birds, as they will appreciate the available food during the colder months. Here are some suggestions for pruning summer-blooming, perennial favorites:
1. Tickseed (Coreopsis): For Tickseed and other shrubby perennials with many small flowers, it is best to shear plants of their spent blooms and buds in August to encourage September and October re-blooming. Deadheading also will discourage reseeding.
2. Daylily: Snap off spent flowers as each one finishes blooming. This action encourages the next flowers to become larger. When the entire stem is finished flowering, cut it down to where the stalk meets the leaves. The same technique can be applied to other flowers on tall stalks such as Hosta, Foxglove, Oriental Poppy and Iris.
3. Garden Phlox: Prune spent flower clusters to encourage the side branches to flower. To avoid mildew on Phlox foliage, thin the stems throughout the growing season to provide better air circulation. In spring, if new shoots seem too crowded, cut out the woody center of each clump. Deadhead the entire plant to the ground when it is finished blooming. Mildew-prone perennials such as Bee balm (Monarda didyma) should be thinned in the same manner.
4. Hyssop or Hummingbird Mint (Agastache): Remove individual flower spikes to keep flowers blooming all summer. When spike is finished blooming, cut it to the ground to stimulate later season blooming. Hummingbirds and butterflies are drawn to these colorful, perennial herbs.
