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posted: 1/26/2013 4:00 AM

Winter a good time to prune dormant trees, shrubs

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  • Lilac shrubs will not bloom in the spring if they are pruned over the winter.

    Lilac shrubs will not bloom in the spring if they are pruned over the winter.

  • Lilac shrubs will not bloom in the spring if they are pruned over the winter.

    Lilac shrubs will not bloom in the spring if they are pruned over the winter.

By Tim Johnson
Chicago Botanic Garden

It may be cold outside, but there still are garden tasks to do.

Winter is a good time to prune trees and shrubs while they are dormant. Overgrown deciduous woody shrubs that need to be rejuvenated can be heavily pruned in January and up until new growth begins in spring.

Start by removing all dead wood. Then prune out as many of the old canes as possible by cutting them at ground level. Leave younger canes that are smaller in diameter, unless the young growth is spindly.

If there are not any young canes in the shrub, cut the large old canes back to 2 to 3 feet from the ground. This will be unsightly at first, 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 that formed flower buds last summer will not bloom when pruned aggressively in winter, because you will have cut off the buds. However, buds will form on the new branches this summer and will bloom the following spring.

So far, we have not had much ice or snow, but there still is plenty of time. If tree branches become covered with ice in a storm, let the ice melt naturally rather than cracking it with a heavy object to try and free the branches. Using heavy objects such as shovels risks damaging the tree bark.

If large evergreen branches are anchored to the ground with snow, you can gently sweep off snow with a soft broom and then elevate the tree branch from underneath. Evergreens that are bent over may be able to be straightened when temperatures warm and the snow and ice melt.

Continue monitoring your garden during the winter for animal damage. Animals can do a lot of damage if their activity is not noticed and stopped. If we get deep snow, it will allow animals such as rabbits to reach higher into shrubs.

Don't forget to water evergreens planted in containers outside during warm spells this winter. Evergreens continue to lose water through their leaves all winter and will be more likely to suffer winter burn if they dry out in the containers. Since we have had little rain or snow, it is especially important to check potted evergreens' soil regularly and supply water.

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

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