Wait to prune perennials until early spring so there is some winter interest in the garden. Some perennials like hostas don’t do well after a freeze, so you may want to cut them back in the fall because they lie flat on the ground. I have a large hosta plant under an oak tree that I don’t cut down in the fall because it lies flat on the ground.
As a general rule, cut back plants that aren’t looking good in late fall and cut back any remaining plants in early spring. If you prefer a clean look to your garden, it’s okay to cut back perennials now. Cut them a few inches from the ground to help support overwintering pollinators.
Consider cutting back more perennials 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 confused with mice. They do not hibernate and are active throughout the year, mostly at dawn and dusk. Voles primarily eat the stems and leaves of various grasses, but will also consume other plants. They eat the bark of trees and shrubs during the winter, causing the most serious damage. Gardens with low landscapes, such as trees, spreading yews, junipers, and huckleberries, have a greater potential for vole activity. Voles are most prolific when they have abundant vegetation. Damage is likely to be more severe during extended cold spells with deep snow cover. Remove weeds and dense ground cover around lawns to make these areas less able to support voles. Mow grass and other grass regularly and cut back vegetation at the bases of trees and shrubs as winter approaches in areas where there is vole activity. It’s also a good idea to pull mulch away from the base of trees and shrubs and keep snow away from the base of small 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 the sod if the ground is not frozen. Grass rolls will freeze during freezing nights, so plan your planting projects while keeping a close eye on the weather. Continue planting bulbs if you are not finished.
• Tim Johnson is director of horticulture at the Chicago Botanic Garden, Chicagobotanic.org.