Cut back perennials in autumn or spring?
Q. How early can I cut down this year's perennials without disrupting the overwintering of butterflies and other beneficial insects?
A. The short answer is … it depends. Until the last few years, our home gardens with their gorgeous spring displays of peonies, roses, tulips and daffodils; summer-blooming daisies; and spring- and fall-blooming clematis were the very definition - even the only definition - of a garden.
Fall cleanup in these ornamental gardens was recommended to discourage insect infestation and to encourage plant health. Plants were cut back in the fall, and the snow covering our yards gave almost no hint of the plant life they held. This is still the pattern where "fall cleanup" leaves a palette ready for the emergence of late winter and early spring flowers.
The "traditional garden" is the most common of the three types of gardens found in the Chicago area. The other types are the mixed garden of ornamental and native, pollinator-friendly plants or the all-native garden. With the coming of spring in late March and early April, crocuses, winter aconite, and green leaves of daffodils and tulips are seen newly emerging.
It's clear from your question, however, that you have a mixed or an all-native "pollinator-friendly garden." Here, plants, leaves, and grasses are left to "overwinter" so their spent stems, seeds and seed pods, flowers and brown foliage - "garden litter" - are left to provide shelter and food for the insects, birds and butterflies (often in their early life stages) that overwinter in the garden home you have provided. The tan garden floor, matted with foliage, with stems standing straight or at an angle, can give the yard a rather haphazard look.
But the goal of this garden is to provide beauty with native plants that replenish our threatened pollinator population - small animals that, without their existence and work, we ourselves would be endangered. Cutting down these plants is optional since they can be left to provide the mulch and fertilizer you would otherwise need in a traditional garden. If you decide to remove this old growth in middle or late spring, remember that many insects are in hibernation or "diapause" so the stems should be carefully bundled, tied and tossed loosely on the compost pile or placed upright against a tree or fence.
Some gardens, of course, are part traditional and part pollinator-friendly, a midcourse that can be the best of both worlds. This is the garden I have - and love!
But whichever garden you have, be watchful for three cool season annual weeds that overwinter here, appear early, and can wreak havoc on any garden: Canada thistle, quack grass and field bindweed. Cutting these plants back to the soil line now will help to control their emergence in the spring.
- Arlene Swartzman
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.