Thinning Out the Crape Myrtle Confusion

I’m not sure which question is most often asked: “What is the best time to prune”? Or… “How do I prune my crape myrtle”? Both are great questions and the one most often asked is, well, I get more questions concerning timing than I do any others. If you look on our web site, there are various discussions regarding timing, seasons and flower bud production, so for now, let’s deal with the second most asked question, “What do I do with my crape myrtle?”

How is this plant spelled, anyways, Crape or Crepe? For our purposes, let's go with the former.

What is this plant all about? It does not occur as a native in the Piedmont but does just a few miles south of us in the Tidewater area. A group of us used to travel to Virginia Beach during the third week in February to play golf. It just so happened that our arrival coincided with the pruning schedule for crape myrtle, and what we witnessed left an indelible mark on my inner xylem that will remain forever.

To perform this pruning task, Virginia Beach pruners use a person that is 5 feet tall; I assumed as a template, and cut all the trees to 5 feet. That’s right, 5 feet, straight across, nice and even. Large cuts, internodal cuts. They were cutting trunks of the trees, (shrubs) by two-thirds! How can this be? Had Dr. Shigo led me astray? Is this not Dr. Appleton’s home and laboratory? Is this not the town that Roger Huff, Urban Forester planted?

We have all seen how crape myrtles are pruned and what they can withstand. They are simply a tough, resilient plant that over the years have filled an important niche in Northern Virginia. Their flowers are rich with color and are spectacular in contrast from plant to plant. Their trunks are rarely round but are more sinewy, resembling an elephant’s trunk or the trunk of an American hornbeam, which is aptly name ‘Musclewood”.

To understand what I mean, you need to see an old crape myrtle. There is one in the gardens of The Mary Washington House in Fredericksburg, VA. This crape myrtle has been cleaned of little else than deadwood and stands sprawling after more than 50 years. You must go see it, and then you will understand the acronym, “A picture is worth a thous…”

Crape myrtle can be used in myriad landscape situations, as long as we respect the first rule of planting; that of giving it the proper place it needs so it can begin its journey unfettered and uncontorted, with an opportunity to reach its genetic potential. There it is again: Right plant, right place. It’s got to happen.

Let’s move!

  • Crape myrtle can be trained to a single stemmed plant or left as multi-stemmed. You can find single stemmed crapes in the nursery so look for one to fit your needs, and you won’t have to remove unwanted larger stems.
  • Crape myrtle is one of the few plants with significant, large flowers that are pruned during the dormant season. Another example is rose of Sharon. They break leaf buds late so you have right up until the first of May to prune them. I would, however try to perform this exciting pruning task in March or April. Crape myrtle flower buds are created on new wood.
  • It is biologically inappropriate and never esthetically pleasing to cut the top off of a woody plant. In fact, please visit our web site and go into articles and peruse the article, “Leave Those Tops Where They Belong”. Topping crape myrtles has earned its rightful name, “crape murder”. It is done everywhere, is not necessary, looks horrible and destroys vital wood necessary for growth integrity. The process of this kind of pruning aggressively invites decay into the wood at each cut. You can redirect a crape’s apical dominance by removing the ends of their extremities but try to do it with a bit more respect to the plant’s architecture. This is called Reduction Pruning and is an accepted industry pruning standard. Have you heard of the term Pollarding? Pollarding is often confused with topping; however, the two are as different as plant and animal. Pollarding, when done with respect to a crape myrtle’s genetic hard wiring is actually a healthful and interesting pruning technique that is in many circles, considered art. We will touch on pollarding a bit later.
  • Crown reduction can be done while thinning the plant, all at the same time. There is a unique pruning trick that can be performed on shrubs and ornamentals that are “cane growers”. Cane growers are plants with multiple trunks or leads. Many viburnums grow this way and can be pruned in a similar fashion. See Cass Turnbull’s book on pruning for more information on cane growers. They are different from plants with single, central leads. Crape myrtles can be thinned beautifully and respond famously. When your crape gets dense and has many conflicting leads simply cut out the offending lead to its point of origination or to a place applicable to relieve congestion. It is that simple. You may take whole leads to the ground or make smaller pruning cuts further out on the lead. The idea is to use your artful eye to allow fewer limbs do the job of many. Now here’s the trick: If you want your crape myrtle to be shorter reach inside the plant and find the lead or leads that are the longest and prune them back to shorter laterals or the ground. This type of pruning is similar to the way we prune old, overgrown azaleas. Pruning in this fashion is not only biologically prudent but showcases the plant’s artful nature as well. Pruning this way creates no heading cuts from which new growth can emerge and most importantly leaves no place for decay to enter the stem. You have also thinned and reduced the plant with one cut. By making a number of these cuts the whole plant can be brought down to another level. As an example simply hold your hand in front of your face and bend your longest finger down, the one between your index and ring finger. You hand is now as short as the next longest finger and thinner because you have eliminated one whole finger. Along the same lines, if your crape myrtle has outgrown its bounds, say leaning over the sidewalk, simply cut the offending lead out of the plant and you will keep the same form the plant had originally but is now less wide. Cane growers give you lots of places to cut and lots of wood to work with. Again, cut out the longest of the leads or limbs in order to thin and reduce at the same time. It’s art, it works and it looks great, and supports a pruning truism: Try to remove the most wood with the fewest cuts possible.
  • If you top or “crape murder” your plant, all the new growth will originate from those cut points and give you an ugly “heading” line. You’ll have the same look you get when you sheer a privet hedge. Internodal cuts are dangerous and usually end up affecting the plant deleteriously. On the other hand, many people believe in cutting all the old seed and flower heads off to give the plant more flowers the next year. If you want to do this, just take the seed and flower heads off by cutting into the smaller wood just below the old flower and seed heads, then thin the plant if necessary. This upper part of the plant is filled with small buds so try to make small cuts when removing the seed heads back to good plump buds.
  • Do we have to remove all your crape myrtle’s conflicting limbs or leads, especially those that are touching? This begs a biological and artful answer. Note: Let me tell you a funny story my college English professor once told me, and remember he said this, not me. He was once asked by a student in class just how long he expected the next writing assignment to be. He answered quickly, “ Your paper should resemble a woman’s bathing suit; it should be long enough to cover the subject yet short enough to be interesting”. I am often asked what is the proper amount to thin from a tree or shrub? I’m afraid I have been guilty of using the above analogy myself. Oh well, we thought it was funny at the time! Back to work, sorry. Branches will sometimes rub against each other, causing a wound where the touch. This wound would be considered natural and part of the plant’s wear and tear. When they rub, depending upon the severity of the contact, a phenomenon called grafting can occur. Grafting occurs when two woody limbs touch and over the years become one branch. It takes a long time but when the branches complete this melding of wood, their xylem becomes one. It makes for wonderful artwork within the tree and in some cases actually helps hold the limbs together. Japanese maples graft limbs successfully as well. If there is great movement between two limbs and the wounding is severe, you may want to remove the offending limb. On the other hand, if the limbs are large and well positioned you may want to allow the plant to graft at that point.
  • Now, just a little on Pollarding. It may look like topping but when this technique is performed correctly, it’s not the same. The International Society of Arboriculture recently published a lengthy journal article that showed the difference between topping and pollarding crape myrtle. Quite simply it demonstrated how decay was able to enter the wood at each cut point when that cut was internodal or between two buds. The definition of topping is exactly that, making a cut that removes a plant’s apical dominance between two buds rather than at the bud. When this occurred the decay moved rapidly and vertically through the crape myrtle stem at each lead where the cut was made. In contrast, when those cuts were made at the point on the stem where there was a viable bud, the wood was able to wall off the decay through the process of compartmentalization and was able to set up a barrier zone because the cut was made properly. This is critical as the first step in pollarding. As you prune, you pick the spots at the height on your crape myrtle you wish the plant to be and that is where you will keep it for the life of the plant. For instance, you may want to keep your plant at five, ten or twenty feet. The plant then begins to grow during the growing season by putting out water sprouts from each cut point. People in Europe used to prune trees this way to produce a constant source of kindling wood for cooking and to heat their homes. Then, during the plant’s dormant season you go in and prune off all the newly developed water sprouts carefully by cutting them off at each sprout’s branch collar. This is critical for successful pollarding. By respecting each branch collar you allow the plant to set up barrier zones so that the plant may, again, establish the compartmentalization process successfully. As the process continues, the years of woundwood that is being formed at each cut builds layer after layer of new wood, successfully sealing out the decay. Your original cut point is now swollen from all the new wood that is being created as a reaction to your cuts. The longer you cut, the larger the swollen knobs become, which gives you the “pollarded” look. It’s quite fascinating but must be done with the plants genetic responsibilities strictly in mind. Please see Dr. Gillman's book on pruning (referenced below) for a more detailed description of Pollarding. Pollarding reminds us how important it is to respect what our plants are telling us when it comes to successful pruning. If we understand how our plants operate as an organism and prune according to the genetic template they have established over millions of years our results will be instant as well as lasting. Knowledge is power when it comes to plant care. We are our plants best friends or we are the enemy, and it all rests in the palm of our hand.

Well, I hope that helps. Try to prune your crape myrtle as you would any other important woody plants in your garden. Plant crapes where they can reach their full growth potential and restrict your pruning to a more hygenic theme rather than one of contortion. It’s nice to have all those flowers that late in the season. Let’s help them stay that way!

Happy pruning, Peter

Recommended Additional Reading:
Tree Pruning by Dr. Alex L. Shigo
An Illustrated guide to Pruning by Edward Gilman, Second Edition

Copyright 2008 by Peter Deahl. All rights reserved.

 
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