It’s happened again. Leaves are getting crispy; flowers are going to seed, and the air is beginning to cool. As hard frosts become a reality, it is almost time to start thinking about cutting back our perennials and putting our gardens to bed.
I’d like to propose that we think about this time of year a little differently. In fact, leaving some perennials and grasses up throughout the winter can be beneficial for many reasons.
One reason not to cut back your plants for the winter is aesthetics. Although it might be hard to watch your plants dry out, turn brown and go to seed (it is for me), when we are deep into the winter season the forms and textures of your plants against the snowy backdrop will look far more appealing.
Piet Oudolf, a world-renowned garden designer from the Netherlands, designs gardens that are meant to be striking through every season, including winter. Oudolf accomplishes this not by using shrubs or evergreens alone, but by using a naturalistic palette of perennials and grasses.
Oudolf selects plants that have characteristics in the winter that most of us never get the chance to experience because we cut them back so early. False indigo (Baptisia spp.), for example, has great winter structure and its seedpods turn a lovely grey-black in the winter, creating an attractive ornamental contrast to the stark winter landscape.
When picking plants to leave, look for stems and seed heads that are sturdy and persist such as globe thistle (Echinops ritro), Siberian iris (Iris sibirica), bee balm (Monarda didyma), showy stonecrop (Sedum spectabile) and Culver’s root (Veronicastrum spp.). Or choose plants with interesting textures such as feather reed grass (Calamagrostis acutiflora), tufted hair grass (Deschampsia cespitosa) and silvergrass (Miscanthus spp.). Experiment with your own plants and take notes so that you can remember what looks best from year to year.
However, before deciding to wait until spring to cutback your plants, consider whether or not the plants are diseased or will re-seed and become a maintenance headache. In these cases, it might be better for the health of your garden and your maintenance plan to cut back these plants in the fall. The same is true if you are concerned about voles or mice overwintering in your beds and causing damage to bulbs and other plants.
In addition to enjoying a winter garden from your window, leaving perennials like purple coneflower (Echinacea purpurea) or black-eyed Susan (Rudbeckia spp.) provide seeds for goldfinches and other winter birds. I have experimented with this in my garden, and it is so satisfying to see the lively birds perched on tiny perennial stems enthusiastically picking seeds from the spiky flower heads.
Leaving perennials and grasses through the winter also offers important protection for insects and pollinators who use the plants and leaf litter as overwintering habitat to help survive the long months of winter.
This fall I encourage you to test this theory out in your garden. Leave a patch of purple coneflowers or black-eyed Susans and see what you think come January. When the world is blanketed in white snow, the texture from your rich black and brown landscape might be just what you need to get you through to spring. And it will definitely help birds and insects survive, too.
By Bonnie Kirn Donahue, University of Vermont Extension Master Gardener