Timing your pruning correctly
March is a good time to prune most trees and shrubs. By waiting until just before new growth begins, pruning wounds are sealed more quickly and there is a reduced risk of cold temperature injury.
Exceptions to pruning in March are spring flowering shrubs like lilac, mockorange, Forsythia, Weigela and some Hydrangeas and Spirea. These are best pruned just after they finish blooming.
Spring blooming shrubs bloom on previous year’s wood. Pruning during winter or early spring removes blooming wood and will reduce or prevent blooming this season.
Summer blooming shrubs like Potentilla, rose of Sharon, St. Johnswort and some types of Spirea and Hydrangea, can be pruned when dormant. These shrubs bloom on new wood that grows each spring.
Some plants create confusion because they bloom on new or old wood depending on the cultivar or species. Hydrangea, Spirea and Clematis are examples. When buying plants, the tag or related information will state blooms on new wood or blooms on previous years wood.
If a plant blooms on new wood, it can be pruned in late winter while dormant. If it blooms on previous year’s wood, pruning at this time of year will reduce flowering. It will not harm the plant, just reduce the bloom.
When it comes to shade trees, March is a good time to prune. The later in March, closer to the start of new growth that a tree is pruned, the better.
You may have heard there is a time when oak trees should not be pruned. This is due to the disease oak wilt. The fungus causing oak wilt can be spread by beetles attracted to sap oozing from tree wounds.
While oak wilt has not yet been found in our area, it is recommended to avoid pruning oak trees from April through June, making March a good time to prune. In this case, the earlier in March is better.
For fruit trees, prune hardy trees like apple, pear and sour cherries first. Wait until later in March or early April to prune less hardy trees like peach and sweet cherry. This will reduce the risk of cold temperature injury to these trees.
As for evergreen trees, it would be best if they were not pruned. Unless you’re growing an evergreen to sell as a Christmas tree, evergreens maintain a more natural shape if not pruned. With frequent shearing, you can end up with a tree that is bare in the center with only an outer shell of green needles.
The only pruning that may be needed for evergreen trees is the removal of a double leader on young trees to avoid structural issues as the tree grows larger. The sooner double leaders are removed on any tree, the better.
For evergreen shrubs like Juniper, Yew and Arborvitae, where size may need to be controlled or if you prefer a sheared form over a natural form, these can be pruned anytime except during very cold weather. Late winter, just before new growth begins is the best time.
When pruning any evergreen, do not prune beyond the green needles on a branch. Most evergreens lose inner needles and will not generate new growth from bare wood. Once an evergreen is pruned too far back, new growth will not occur to cover bare areas.
Kelly Feehan is a community environment educator for Nebraska Extension-Platte County.