By: Steve Houser
In order to know how to properly prune any plant, a basic understanding of the characteristics and growth habit of the plant in our area is required. A Crepe Myrtle is not quite like any other local plant in how it grows, and is therefore not like others when considering how they can be pruned. A Crepe Myrtle is an ornamental plant that blooms profusely throughout most of the growing season. They can grow to over 25’ tall, are very hard wooded and the small twigs or old seed pods do not produce new growth in the spring (like most plants). Tip growth normally dies back approximately 7-12 inches in the winter months. If a Crepe Myrtle is not tip pruned by spring, the new growth will emerge approximately 7-12 inches from the old seed pods. This leaves dead tips as it emerges in the spring. Since Crepe Myrtles are rapid growers, the new growth will rapidly obscure the view of the dead tips within a few months. The dead tips are of no great consequence to the overall health of the plant. Aesthetically, the dead tip is not attractive for the first few months of the growing season. They are also known for producing root sprouts that grow upward from the outward growing roots or near the root collar (or root crown).
The three factors that must be considered in the pruning of Crepe Myrtles are health, aesthetics and cost or time to maintain the desired condition.
Crepe Myrtles are hardy plants that can sustain moderate freeze damage or severe reductions in size (even to the ground level) and in most cases, still grow back. Crepes that are planted north of our area can encounter freeze damage to the top growth, but are like an annual in that they can grow back from their roots. From a pure health prospective, they should be maintained in the same fashion as a shade tree by removing crossing limbs and canes (if practical), removing root sprouts, structural pruning, and basic deadwood removal. This type of pruning can be done anytime of the year and is the most beneficial to the long term health and longevity of the plant
From an aesthetic point of view, tip pruning of Crepes can be utilized to make them more attractive. Proper tip pruning should be accomplished in late January thru March, but not after the new shoots have emerged in the spring. Current research shows that tip pruning (or heavy pruning) at other times of the year, may increase the odds of freeze damage. Tip pruning should be to approximate pencil size twigs and in a rounded form. Some Crepes may end up columnar in shape, but in any event, the top growth should not be cut flat because it encourages all the blooms to be at one height. Severe cutting back is not attractive, reduces food storage, encourages poor branching structure and should be avoided. Since all Crepe Myrtles will have dead tips in the spring, removal of pencil size twigs avoids viewing the dead portion and is more aesthetically pleasing. The best show of flowers can be obtained by constantly removing the spent seed pods (dead heading) throughout the growing season, although it can be very time consuming.
The amount of time (or cost) required to achieve a positive effect is much less for small (or medium) size Crepe Myrtles. Large or tall Crepes can be structurally pruned as noted above, however, tip pruning can be very time consuming (or costly) and is not of much benefit to the overall health. Severely cutting back the trunks will reduce the amount of time (or cost) to maintain them, but it is not what is best for the plants structure or health.
In summary, if you are concerned about only health, prune it like a small shade tree. If you are concerned with the aesthetics, prune it like a small shade tree and also tip prune. If you really want show, prune the seed pods as they die. Each step beyond leaving them alone involves more time and cost. What is right for you depends on your personal preference, the characteristics of the plant, the site and of course, and the budget.