Bram Franklin and Neil Sperry, Board Members, The Crape Myrtle Trails of McKinney
A great percentage of the pruning done to crape myrtles annually is either unneeded or done incorrectly. What has taken Nature years to produce, we can ruin in mere minutes through improper pruning.
"Topping" crape myrtles is always a bad plan.
Pruning Facts to Know Before You Start:
- Always prune with a purpose. Know exactly where and why you are making each cut on your crape myrtle.
- Never use pruning as a means of height control for crape myrtles. It is never proper "to prune standard crape myrtles back." In other words, never "top" any large crape myrtle at any time for any purported reason.
- All crape myrtles are, by their nature, shrubs. As landscapers taught us beginning in the 1950s and early 1960s, we can remove lower branches of taller types so that they will look like small trees. However, they will continue to send up sprouts around their bases. If you do not remove those sprouts as they develop, your plant will revert to growing shrub-form.
- Crape myrtles flower on new growth. That is counter to most other flowering shrubs that produce their buds and blooms on the prior year's growth.
- You can often stimulate additional new growth and second, third and even fourth rounds of flowering by removing spent flower heads as soon as the last petals have fallen. Allowing them to go to seed will slow or halt further flowering for that growing season.
- You can remove old, dried seed heads during the winter if you wish, but it is only cosmetic. Crape myrtle branches will always die back by 6 to 8 inches each winter. Even if you do not remove the seedpods, the new growth will begin at the bases of the dead twigs. That new growth will quickly overtake the parts that have died back.
Time to Prune
It is easiest to prune crape myrtles during the winter while they are completely dormant. That's the best time to see their branching structure, so that's the best time to identify and remove limbs that are damaged or that are beginning to rub against one another. However, you can actually prune crape myrtles to remove unwanted branches and basal sprouts year 'round.
You will need a pair of bypass hand shears, a pair of long-handled lopping shears and a small pruning saw. You will probably occasionally also want a long-handled pole pruner to reach high into tree-form crape myrtles. Take care of your pruning tools, keeping them clean, sharp and well-oiled. Store them in a dry location when you're not using them.
Make each cut flush with another branch or with the main trunk. Never leave stubs larger than a pencil-width in diameter when cutting any part of a crape myrtle. That rule alone will prevent topping of crape myrtles, known by many as "crape murder." It is singly the worst and most threatening practice in routine crape myrtle maintenance.
Prune above buds and twigs that face out from the center of your crape myrtle. Those will be the new shoots that will develop. Your goal is to encourage open and spreading growth so that limbs won't rub together, also so that air movement will not be impaired to the centers of the plants. Powdery mildew is a threat to crape myrtles, and overly dense canopies encourage its development.
If you are trying to train a somewhat mature shrub-form crape myrtle into a tree shape, determine first which of the trunks will become the structural trunks of the new tree, then prune and remove all the rest completely to the ground. You will want 3 or more trunks, and odd numbers of stems are visually more appealing. They will try to resprout the following spring, but just keep them pruned away.
Tree-form crape myrtles have been developed from what were genetically shrubs.
As your young crape myrtle tree begins to take its shape, gradually remove side branches so that the trunks become more visible. At any given time you will not want to remove side branches more than half-way up the trunks. They are important in the plants' overall vigor, so leave them in place as long as you can. This pruning can be done at any time and it's known by commercial growers as "trashy trunk," where the shoot stubble is left on the trunks to help them thicken.
You may want to develop single-trunk crape myrtle trees, known commercially as "standards." The process is exactly the same, except you choose the single straightest, best trunk and encourage it to develop. You will need a stout stake alongside it to keep it bolt-upright as it grows. It is considerably more challenging to produce standard crape myrtle trees than it is those with several trunks. You must also be careful to keep their tops well-balanced in ensuing years so that they don't begin to lean and lose their symmetry.
Mature, established crape myrtles do not require annual pruning. However, you may want to thin the internal branching. Crape myrtles can become very dense with several branches vying for the same space and sunlight. Thinning opens the plant's canopy up, but it does not change the plant's overall profile when viewed from the side. It allows you to remove rubbing branches before they are both ruined.
Restoring a Topped Crape Myrtle
It may seem extreme, but, if you have a tall crape myrtle that has been topped, the quickest way to get a great-looking plant back again will be to cut the trunks completely back to the ground. You will be absolutely amazed at how quickly they can regrow into straight, new trunks. Usually you can have a fairly mature-looking plant within 12 to 24 months. That's far quicker than trying to coax new branches to conceal the effects of a prior topping.
Crape myrtle sprouts that will be trained as new trunks once plants are cut completely to ground.
A Special Exception in Crape Myrtle Pruning: The following advice may seem contradictory in pruning crape myrtles. Dwarf crape myrtles (those that stay 4 to 5 feet or shorter at maturity) can get rather lanky when allowed to grow to full height. Since you will never be developing them as trees, you may want to keep them as short and compact as you can. Not unlike the woody perennial butterfly bush, dwarf crape myrtles can be cut to within 10 to 15 inches of the ground each winter, almost like leggy perennials. They will regrow vigorously in the spring and begin blooming on their new growth by summer. However, extreme pruning of this nature must be used only for the very short varieties, and only when they tend to grow gangly without it.
Research has shown that pruning sealant can actually slow the healing of cut branches. It is usually best not to apply it to crape myrtles as you trim them.
The Crape Myrtle Trails of McKinney strongly encourages you to ask plenty of questions before you prune (and possibly ruin) your crape myrtles. Your local nurseryman or Extension agent can also help.
Unusual Freeze Damage from Tennessee
Crape myrtles in Tennessee were dealt a devastating blow when a hard freeze on April 9 caught them leafed out and starting to grow. Stem tissues froze and cracked from the abrupt changes. Ice crystals soon formed in the frothy sap and in the moisture that accumulated within the cracks. The only recourse was to cut the frozen plants completely to the ground immediately, then retrain any new shoots into the plants' former forms. For the record, this type of damage is not confined only to crape myrtles. Even light freezes that occur after plants are growing actively can kill tissues that normally would withstand winter temperatures 25 or 35 degrees colder. This was a fluke that hopefully will not be repeated anytime soon.