Perennials can provide lovely landscape throughout winter
Wait to cut back perennials until early spring so that there will be some winter interest in the garden. Some perennials such as hostas do not look good after being frozen, so you may want to cut them back in fall as they flatten to the ground. I have a large hosta under an oak tree that I do not cut in fall as it flattens to the ground.
As a general rule, cut back plants that do not look good late in the fall and cut back the remaining plants in early spring. If you prefer a clean look in your garden, it is OK to cut perennials back now. Cut them back a few inches from the ground to help support overwintering pollinators.
Consider cutting more perennials back in the fall if you have had problems with voles in the past. Voles are small rodents with stocky bodies, short legs, and short tails that can be mistaken for mice. They do not hibernate and are active throughout the year, mostly at dawn and dusk. Voles primarily eat stems and leaves of various grasses, but they also consume other vegetation. They eat the bark of trees and shrubs during winter, which causes the most serious damage. Gardens that have low-lying landscaping, such as arborvitae, spreading yews, junipers and cranberry cotoneaster have higher potential for vole activity. Voles are most prolific when they have abundant vegetation and cover. The damage is likely to be more severe during extended cold spells with deep snow cover. Eliminate weeds and dense ground cover around lawns to make these areas less able to support voles. Mow lawns and other turf regularly and cut back vegetation from the bases of trees and shrubs as winter approaches in areas where there is vole activity. Also, it is a good idea to pull mulch away from the base of trees and shrubs and keep snow cleared away from the base of young trees. Reducing cover makes voles more vulnerable to predators such as hawks and owls.
In general, removing cover is very effective in preventing vole damage.
You can continue to install sod if the ground is not frozen. The rolls of sod will freeze during subfreezing nights, so plan your sodding projects with a close watch on the weather. Keep planting bulbs if you have not finished.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.