To cut back perennials or not to cut back perennials, that is the question many gardeners ask themselves in fall. We have been fortunate this autumn that the weather has been unusually warm in Minnesota, which is giving many plants a last shot at blooming. (Many of my daylilies re-bloomed in September and October and a single spirea shrub is just about to bloom even now.)
Still, you do not want to leave all your plants standing in the fall, and I have noticed an increasing number of gardeners who are inclined to cut back rather than leave perennials standing. The main argument you hear in favor of leaving perennials standing through winter is that they create winter interest — and some do. I like sedum in snow and at least for awhile many grasses look nice, especially when coated in hoar frost. More importantly, some standing plants provide habitat for beneficial insects or food for birds. I leave many native plants standing (coneflower, rudbeckia, liatris) because they are beneficial to insects and birds. I also leave sunflowers standing all through winter, even though they look terrible, because I know birds will devour the seeds. The other (often unstated) reason people do not cut back in fall is they are tired. It’s cold, it’s windy, and you’ve gardened enough for now.
Why cut back? First, it gives the garden a neater appearance in winter and it may reduce the prevalence of some diseases the following spring. The University of Minnesota recommends strongly removing any diseased foliage and bringing it to a municipal compost pile. (Most home compost piles do not heat up enough to kill the pathogens in diseased plant debris.) Doing garden clean up in the fall also decreases the amount of work that will have to be done in spring. Some plants are just disgusting to clean up in spring if left all winter, especially hostas, which get soggy.
What’s your attitude toward cutting back in fall?