Now that we’ve had frost it’s time for some fall cleanup in our landscape. Once frost kills their foliage, plants are finished storing food and won’t need their leaves any more until spring. Whether or not (or how much) to cut back perennials for winter depends on the individual plant, and also on your feelings about “winter interest” and wildlife in your garden.
WHY TO CUT PERENNIALS BACK: The main reason is that having a lot of dead foliage can harbor diseases or insects, like mildew on Bee Balm, botrytis on Peonies, or borers on bearded Iris. We recommend raking large leaves like Maple or Sycamore because they can mat down and hold water, causing crown rot on perennials. Cleaning out your beds discourages rodents from nesting and devouring your plants during the winter months. Clean perennial gardens also look neater, which is the most frequent reason to clean things up for winter.
WHY NOT TO CUT PERENNIALS BACK: Perennials in the winter landscape are important resources for birds and butterflies. Praying Mantis, butterflies and moths lay eggs or pupate in the shelter of dead foliage, so your cleanup efforts can actually destroy the eggs and larvae of desirable insects.
Ground birds find food and shelter in dormant perennial crowns. Birds such as finches, juncos, chickadees, cardinals, nuthatches, sparrows and red-breasted woodpeckers depend on seed heads for winter forage. Dead blooms of coneflower, black-eyed Susan and many other popular perennials attract winter birds, a key to their survival when the ground is snow-covered and bird caloric needs are greatest.
Another reason not to cut down dormant perennials is that their foliage provides insulation from the cold, protecting the plants from winter kill. Research has shown that tender perennials such as Mums, Asters, Ferns, Lavender, Russian Sage, Armeria, and oriental Poppies will survive extreme cold much better if left unpruned. Perennials that remain green through the winter like creeping Phlox, Liriope, Christmas Fern and Hellebore are better left alone until spring.
ROSES: Most Roses are best left alone right now, since freshly cut branch tips will die back during winter and will need trimming a second time in spring. Rose experts typically recommend pruning after new growth buds start to open, except for climbing roses which should only be pruned after they bloom. We do recommend cleaning leaf litter from around roses since it can harbor disease.
ORNAMENTAL GRASSES: Some grasses look good all winter and are best left alone until spring. If they appear messy, or if they are brittle and make a mess during the winter, you can cut them down to about six inches any time now. There’s no harm in cutting them back anytime, but they will give you winter interest and privacy screening if left uncut.
FALL FEEDING: This is a good time to apply slow-release fertilizers around plants. This gives time for the plant food to be absorbed into the soil, even though plants won’t start feeding until spring. We recommend balanced, multi-mineral fertilizers like Espoma Plant Tone® and Holly Tone®, which will not burn plants.
Steve Boehme is a landscape designer/installer specializing in landscape “makeovers”. “Let’s Grow” is published weekly; column archives are online at www.goodseedfarm.com. For more information call GoodSeed Farm Landscapes at (937) 587-7021.