Pruning overgrown shrubs best done when they're dormant

Winter is a good time to prune trees and shrubs. Overgrown deciduous woody shrubs can be aggressively pruned this and next month to rejuvenate them.

Start by removing all dead wood. Prune old canes off at ground level, leaving several young canes. You may need to cut back the remaining young stems if they are spindly and flop over.

If there are not any young stems, cut the large canes back to 2 to 3 feet from the ground or to a point where there is a young stem. Many gardeners are hesitant to prune as aggressively as needed for best results. This will be unsightly, but if the plants are healthy, extensive new growth should start from the old canes in spring and fill in the plant.

Shrubs such as lilacs, forsythias and viburnums that formed flower buds last summer will not bloom when pruned aggressively in winter. Pruning to rejuvenate overgrown shrubs is best done when they are dormant, even though one season of flowers will be sacrificed.

• It is best to keep any logs you saved for burning in the fireplace outside until you are ready to burn them as insects can come in with the firewood. Never treat firewood with insecticides.

• Keep monitoring your gardens for animal damage. There has not been much snow this year to notice animal tracks so take a walk around the garden to check on your plants.

For example, deer tracks in the snow are a reminder to go out and check plants. If future snowstorms build up snow levels, rabbits can reach higher into to shrubs to feed. Yews and arborvitae are a couple favorites for deer to browse.

Install garden netting secured by tying to the plants as needed to protect them.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.