University of Illinois Extension

Preparing Perennial Beds for Winter

“Autumn is the time to prepare perennial flower beds for winter. In autumn, watering should be done on a continuing basis until the soil freezes and can no longer accept water,” said Sharon Yiesla, U of I Extension horticulturist. “Keeping plants well hydrated helps to maintain a good root system. It is from this root system that the plant will re-sprout next spring.”

Good watering, Yiesla noted, should consist of an inch of water every week between rainfall and irrigation provided by the gardener. Supplying that water in a good, deep, once-a-week watering is far more beneficial than sprinkling every day or two. A deep watering will encourage a deep, strong root system.

Remove weeds from the garden before winter.

Sharon Yiesla

“Remove weeds from the garden before winter,” she said. “Although these plants will not be growing in winter, they can act as an overwintering place for various diseases and insects. Removal of the weeds helps to reduce certain pest problems for the following growing season.”

As plants begin to decline and head toward their winter dormancy, gardeners should think about cutting the plants back to the ground.

“This activity may be spread out over a number of days or weeks since all perennials do not go into dormancy at the same time,” Yiesla said. “As plants decline in appearance, they can be cut back to the ground. Since most perennials will re-sprout from the root system, there is no need to leave tall stubs of old stems in the garden. Cut stems down close to the ground.

“There are a few perennials that tend to be semi-evergreen, and these may not need to be cut down until after winter has passed.”

If the gardener chooses, cutting the plants can wait until spring. Some plants, when left in the garden, can provide winter interest, act as snow collectors (for insulation), and may provide food for the birds. When choosing to leave plants uncut in the winter garden, the gardener must be willing to set aside some time in the spring to do the cleanup.

“Applying mulch in the fall can help insulate the garden soil through the winter,” she noted. “Before mulching, see how much mulch is left in the garden from spring applications. Overall, about two to three inches of mulch is sufficient.”Gardeners often mulch too early, applying mulch to soil that is still very warm, she added. Instead, wait until a couple of frosts have occurred and the weather is becoming consistently cooler. This signals that the soil is also cooling. Add mulch to obtain that two to three-inch layer on the ground around the perennials. Do not cover perennials with mulch or pile mulch around their bases as this may lead to excess water accumulation and rot the plant.