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Saturday, March 2, 2024
March 2, 2024

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Gardening with Allen: Fall is a good time to prune some shrubs


I have a number of shrubs that have become too large. Is now a good time to prune? How can I prune to achieve a natural look? I don’t like artificial-looking balls and boxes.

Fall is an excellent time to prune. Plants are becoming dormant. As deciduous plants lose their leaves, it is easier to see where to make pruning cuts. However, spring-flowering shrubs such as rhododendron, azalea, pieris, lilac, spiraea, and forsythia have set their flower buds for next spring’s bloom. Wait until after they bloom to prune them so you don’t remove next spring’s flowers.

You cannot achieve a natural look by using power clippers or shears that prune multiple branches with one cut. Although it takes more time to prune one branch at a time, that is the only way you can achieve a natural look.

The tip bud on each branch is dominant to the lower buds on a branch. When the tip bud is left, it will suppress the growth of the buds below it. Usually it is the only bud that will develop. Occasionally one or two buds well below it will also grow. If the tip bud is removed leaving other buds below it, three or more buds will grow into branches.

If a branch is pruned just above a side branch, the tip bud on that branch becomes dominant. It is usually the only bud that develops, so there is only one bud stimulated to grow instead of three or more.

If a branch is pruned clear back to where it originates from a larger branch, normally no new branches are stimulated to grow.

To summarize, there are three types of pruning cuts. Each type gives different regrowth results. Pruning just above a bud results in three or more new branches. Pruning just above a side branch results in one branch for each branch removed. Pruning back to a branch origin thins the shrub.

When shrubs are sheared, it stimulates multiple branch regrowth. This results in thicker and smaller growth. We shear hedges because we want thick growth. We also usually want a uniform geometric shape.

In most cases we want shrubs to maintain their natural thickness, so we prune most branches back to a side branch. That keeps the same natural thickness.

When growth becomes too thick, such as when power clippers have been used, then removing whole branches back to their origin is the primary pruning cut.

If one part of a shrub is too thin and open, you may want to tip prune, leaving several buds below the pruning cut to encourage thicker growth. By using these three cuts at appropriate times, you can achieve a natural look on any shrub.