When to prune Spirea
Question: Is it OK to prune spirea now or should I wait until spring? It has pink flowers and blooms in summer. Should lady’s mantle be cut back now? B.B.
Answer: Pink spirea (i.e. Anthony Waterer, Froebel, Goldflame) is a “parking lot island shrub”. Parking lot shrubs can be sheared off by snow plows or crushed by snow then come back and bloom the following summer. You can prune all the stems of pink spirea back to 3 to 4 inches tall. Then, cut the largest stems out at the crown. This pruning can be done anytime the plant is dormant, basically mid-October to late March. Vigorously growing plants can be pruned yearly but I prefer to use this method every two to three years.
Dormant pruning of spring blooming spireas, which are usually white flowered, will cut off flower buds. The best way to prune them and other multi-stemmed spring flowering shrubs is cut out one-third of the largest stems at the ground line shortly after they bloom. Many of these shrubs tolerate being completely to the ground in winter but you sacrifice flowers the following spring.
Lady’s mantle (Alchemilla) and other herbaceous perennials die back to the ground every winter. Then resprout from the crown and roots in spring. Most perennials, including lady’s mantle, overwinter best if left alone in fall. Their stems catch snow insulating the crown from temperature extremes. Many herbaceous perennials add texture to the winter landscape. Native perennials and ornamental grasses provide food and shelter for wildlife. In March carefully trim herbaceous perennials back to the ground taking care not to damage new shoots.
Of course, there are exceptions to the “leave ‘til spring” policy. Diseased plants should be completely cleaned up and removed from the garden in fall. Hosta and other perennials that mush down to a dense mat are ugly and may hold to much moisture near the crown, so clean those up. Insect prone or infested perennials, like German iris, are another fall clean up must. Although I don’t always get around to it, chrysanthemums and mints are susceptible to disease and winter damage and should be cut back to the ground in late October.
Tip: Voles or meadow mice damage trees and shrubs by eating bark during winter. Remove their hiding places by pulling the mulch back several inches away from trunks of trees and shrubs. Protect trunks of young fruit and ornamental trees with plastic tree spirals or hardware cloth.