Too often crape myrtles are cut back to bare trunks in the belief this abuse will yield more flowers. More flowers? I've seen very few crapes that have a problem in the "bloom" department. In reality, this type of severe pruning results in a shorter bloom time, delayed flowering, weaker branching, and can increase insect and disease problems. This practice, also known as topping, is harmful to all trees and is never the right way to prune a crape myrtle. I've included a link from the Univeristy of Arkansas that addresses this topic at the bottom of this page. If your landscaper recmmends topping your crapes, have them call me and I'll fire them for you.
Photo/Illustration by: Melissa Lucas
Prune for Health
Late winter (February-March) is the best time to prune crape myrtles in Fort Smith, Arkansas. Like all trees, the correct way to prune a crape myrtle involves enhancing its natural form rather than trying to force it to grow in a space that is too small or an artificial shape. Crape myrtles naturally grow as small upright or vase shaped trees with multiple trunks. In a well pruned crape myrtle, the trunks grow upward and outward, with branches fanning out rather than growing inward into the center of the tree.
To determine if your crape myrtle needs to be pruned, examine the direction in which the trunks and branches grow. Starting at ground level, follow the trunks upward to where they begin to branch, focusing on the interior of the tree rather than the outer edges. Branches that grow into the center of the tree, crossing over other branches or trunks, should be removed.
To remove a branch, follow it back to where it joins a larger branch or trunk. Take a close look at the point where the branch joins the trunk. You will notice at the point where the two join the branch is swollen or enlarged. This area is known as the branch collar. Using a pruning saw, remove the branch by cutting just above the branch collar rather than flush with the trunk. If the branch was removed at the correct place the branch collar left behind will extend out a centimeter or two from the trunk.
If it has been years since the tree was last pruned you may have to remove several branches. Whole trunks can be removed by cutting them off as close to ground level as possible, but this results in profuse sprouting of suckers during the summer and should be done only as a last resort.
If you have the time and the tree is not too large, you can clean up the interior of the tree by cutting off small twiggy branches that grow from the main trunks. This is best done using hand pruners. You can also remove seed pods and trim off the ends of branches that are less than pencil sized in diameter. While these practices will help the tree look neater and may increase the size of flower clusters, they are not necessary to keep the tree healthy.
Reducing Tree Size
Crape myrtle varieties like ‘Natchez’, ‘Muskogee’ and ‘Tuskegee’ easily reach twenty five feet tall or higher with a similar spread. If you have planted a large growing variety in a space that is too small to allow it to mature your best option is to move the tree to a different spot and replace it with a more compact selection such as ‘Tonto’, ‘Sioux’ or ‘Catawba’, which grow to fifteen feet or less.
If moving the tree is not an option, you can reduce tree height and width by cutting back the tallest and most wide spreading branches at the point where they join another branch. Known as reduction pruning, this method preserves the natural shape of the tree and is infinitely preferable to topping.