Fall Pruning

Pruning in the FallQuestion: I read recently that fall is a good time to prune trees and shrubs. I have a variety of plants which need attention. What can I prune now?

Answer: Yes, fall, after plants have become dormant is a good time to prune many plants. Late October and November is a good time. Some pruning can even be done in the winter when temperatures are above freezing.

You can prune all evergreen conifers now–both trees and shrubs. Virtually all deciduous shade and flowering trees can be pruned now. Avoid pruning most flowering shrubs which bloom in the spring. This includes Forsythia, Lilac, Spiraea, Mock Orange, Flowering Quince and Viburnum. These shrubs have already set flower buds for next spring and pruning now will remove some of them. However, pruning a few branches which stick out would be acceptable. Summer flowering shrubs such Potentilla can be pruned now.

I also avoid pruning any trees and shrubs which have marginal hardiness. This includes most fruit trees and roses. During the past few years as climate has become warmer, many plants rated for zone 5 and 6 hardiness have been planted in eastern Idaho, even though our official plant hardiness zone rating is 4. These should only be pruned in the spring, since pruning now delays dormancy and makes them more susceptible to winter cold.

One of my favorite pruning methods is the one-branch-at-time method. I look at a tree or shrub and select one branch which extends beyond the outline or silhouette that I want. I follow that branch back inside other surrounding branches and cut it off just above a side branch where the stub will not show. Then I select the next branch which sticks out and prune it the same way. After pruning several branches, I have reduced the size and given it a more uniform shape. But it still retains its natural shape and thickness.

Sometimes branching of trees and shrubs becomes too crowded, with branches growing into each other. Where two branches rub against each other, one can be removed clear back to its origin. I usually favor keeping branches which are growing outward and remove those which are growing upward or inward.

By contrast, pruning all branches to the same length leaves unattractive stubs. Each of these stubbed branches will produce 3 or more side branches next year, making the shrub artificially thick. Unless you want formal looking balls and boxes, avoid pruning shrubs with power clippers or shears.

Most shade and evergreen trees are strongest and look best with a single trunk or leader. If you have 2 or more upward growing branches near the top of a tree, it is best to leave the most upright one and shorten or remove the others.

When removing a large branch from a tree, leave a slight collar where the base of the branch flares. This contains the tissue for healing of the pruning wound. Do not apply wound dressing or paint to pruning cuts. It only delays the healing process.

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