As soon as trees start turning color in fall, many gardeners start to think about pruning their trees and shrubs. At best you can clean, sharpen and adjust your pruning tools. Now, however, is not time to do much major pruning of your plants.
It is always time to prune dead, diseased, damaged (broken) branches off your plants. It is easier to identify these problems when the plants are growing, than after the leaves have fallen off. You should also remove suckers from the bottom of plants as soon as you notice them. Suckers are vigorous shoots growing off the tree or plant from below the bud union.
In general, most deciduous plants (plants that lose their leaves) are best pruned in late January, this includes fruit trees, deciduous shade trees and roses. This is the optimum time to prune this group of plants. It will not hurt to prune your fruit or shade trees as soon as the leaves have fallen off, however your trees will not start to heal until the plant starts growing next spring.
Spring blooming plants like forsythia, lilac, lady banks roses or plants that flower in spring or early summer are should not be pruned in winter but wait and be pruned after they bloom, which would be next spring. Flowering peach, flowering cherry and flowering crabapple should be pruned immediately after they finish blooming next spring. This allows you to have a spectacular flower show in the spring. After the plant has finished blooming then they need to be pruned. For most of these plants, that would have been late spring or summer. If you prune these plants during the winter, you are just removing the future flowers buds and decreasing the flower show for the coming season.
The best time to prune evergreen trees and shrubs is during the plant’s growing season, which is mainly spring through fall. This allows the plants to heal quickly. Evergreen trees and shrubs are plants that do not lose their leaves in the winter. This includes pines, junipers, magnolias and other plants that have leaves on the plant year-round. There are two types of evergreen plants, broadleaf evergreens and conifers. Broadleaf evergreens are typical landscape shrubs like Indian hawthorn and privet. Conifers are cone-bearing plants like pine trees, junipers, and cypress. Broadleaf evergreens can be pruned anytime but are best pruned after they flower. Conifers are best pruned during their growing season, which is fall and spring.
Herbaceous plants like daylilies, fortnight lilies and ornamental grasses are best not to have the dead or damaged leaves removed until next spring. Even though the dead leaves look bad on the plants during the winter they insulate the roots. Removing the dead leaves during the winter could actually kill the plants, by allowing the roots to freeze. Examples of herbaceous plants include agapanthus (lily of the nile), daylilies, fortnight lilies, yarrow, asparagus fern and Shasta daisies, to name a few.
If your first impulse is to grab the pruning shears and attack your landscape shrubs, roses and fruit trees, stop! It is best not to prune any plants until the end of January.