Prune trees and shrubs now to rejuvenate

Winter is a good time to prune trees and shrubs because you can easily see structural problems to correct and be more aggressive in your work without creating undue stress on the plants.

Overgrown deciduous woody shrubs can be heavily pruned to rejuvenate them this month and next.

Start by removing all dead wood. Prune old canes off at ground level if possible, leaving several young canes to form the future structure of the shrub. You will need to cut back the young growth, especially if it is spindly and flops over once the large stems are removed. Cutting it back will also encourage more dense growth and bring the shrub into proper scale.

If there are not any young canes or not enough of them to form a new shrub, cut the large canes back to 2 to 3 feet from the ground. 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.

After pruning, Shrubs such as lilacs, viburnums and forsythia that formed flower buds late last summer will not bloom the following summer. The aggressive pruning will have removed all the flower buds. Viburnums and lilacs tend to form flower buds at the ends of the branches so even a general light pruning of these shrubs can remove a significant amount of the flowers.

Do some research on your shrubs so you understand the impacts your winter pruning will have on their flowering in the coming spring and summer. Panicle hydrangeas flower on new growth so they will respond well with great flowering when they're cut back in the winter.

• Keep monitoring your gardens for animal damage that can still be occurring even without snow. The snow makes it easier to see tracks, which give you a reminder to go out and check things. Rabbits can reach higher into shrubs to feed as snow levels build up. Yews and arborvitae are a couple of favorites for deer to browse. Install garden netting as needed to protect your plants.

•If tree branches become covered with heavy snow that is frozen, let the snow melt naturally rather than cracking it with a heavy object and damaging the limbs. If large evergreen branches are anchored to the ground with snow, gently sweep off snow with a soft broom and then elevate the tree branch from underneath. It is best to remove the snow as it falls or shortly after it ends, before the snow gets frozen to the branches. Using heavy objects like shovels risk damaging the tree bark, creating a possible point of entry for infection and insect attack.

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