Spring has been a long time coming this year. But the wait is over, and the next month will bring an especially vivid carnival as delayed blooms join those unfurling on schedule.
This floral parade may help distract us from a widespread practice that reaches its peak in March: the mutilation of crape myrtles, a deed that arborists label “crape murder.” Avert your eyes and look at those cherry trees.
The crape myrtle has always brought out the inner butcher in certain people — there is something about those smooth, sinewy branches that screams “amputate me” — but crape murder has become much more prevalent in recent years simply because crape myrtles have become ubiquitous. Once a marginally hardy tree or big shrub for the Deep South and the beach, new varieties have been bred to expand the tree’s range into what might be called Maim Street USA. Crape myrtles are now commonly planted in residential and commercial landscapes, and even as street trees. With this tree’s spread has come the idea that it needs to be hacked back. Removing mature branches this way disfigures the crape myrtle, causes decay and sets into motion a time-consuming annual chore of removing the rank growth triggered by the previous year’s sawing.
So why is it done? The short answer seems to be “because everyone else does it.” That includes landscaping crews who move through commercial and residential landscapes at this time of year, only to leave a forest of stubs.
As many as two-thirds of crape myrtles in a neighborhood will get the chop. “It makes people comfortable, when they are doing what many others are doing,” said Edward Gilman, a professor of environmental horticulture at the University of Florida. “The way people prune trees in the U.S. is largely not rooted in science. A lot is culture-based.”
If you did this in winter to, say, a flowering dogwood, you would lose the spring blossoms. But the crape myrtle blooms in high summer on fresh growth, so the assault is soon masked. It is its rare ability to bloom through the cauldron of summer that has made it so popular, although its greater ornament to many eyes is the beauty of its peeling bark. In some varieties, the bark is a warm cinnamon hue; in others a medley of patterns and colors.
These sculptural qualities reward artful pruning, but fine pruning is one of those horticultural skills that must be mastered. Don’t assume a landscaper knows what he is doing. To see how crape myrtles should be pruned, see the mature specimens near the administration building at the U.S. National Arboretum.
One rationale for crape murder is that a tree has outgrown its space, or that its flowers are too high in the canopy to enjoy. To which experts respond: Plant a smaller variety. Crape myrtles are available in many forms, from dwarf shrubs that grow to four feet or less to trees that can exceed 30 feet. Unfortunately, one of the most popular varieties, the white-flowered Natchez, matures to 25 feet high or more and 15 feet across.“If you have Natchez you’re going to be a little bit up a creek if you want to keep it at 10 to 15 feet,” said Mary Olien, manager of Green Spring Gardens horticultural park in Northern Virginia.
“There’s a crape myrtle for every location,” said Peter Deahl, a certified arborist from Sterling who gives courses on proper pruning methods. “If you put the right one in, all you have to do is thin it every couple of years.”
To be fair, many of the outsize crape myrtles were planted by players who have moved on, leaving current residents and landscape managers to deal with the consequences.
But through correct pruning techniques, oversize crape myrtles can be reduced in scale without resorting to topping, the name for arbitrarily sawing back mature branches. By removing lower branches, best done when the tree is still young, you can make the tree’s habit narrower and less in conflict with nearby walls or paths. Some varieties naturally are more upright in their habit and need a smaller footprint.
Another rationale for topping is that it cleans up all the twiggy seedpods evident in winter. These can be removed with a far less intrusive technique known as tipping, which removes some of the upper twigs to a lower branch union. Even this is unnecessary: The seedpods can be left alone because they are soon hidden by spring growth and will shed in their own time.
Reputable tree companies employ a technique known as crown reduction to lower the height of a tree without mutilating it. It is essentially a two-step method: Some of the upper branches are removed, and the remaining ones are shortened to a point where they meet a lower branch or an outward-facing bud.
Both tipping and crown reduction work with the tree’s biological structure to keep its natural appearance and to assure that subsequent growth is healthy. Topping does not.
Trees react to topping by sending up rank growth during the next growing season, sprouts that can reach eight feet long and frustrate the intention to lower the canopy.
Gilman and his colleague Gary Knox studied the effects of pruning on Natchez crape myrtles and found that trees that were topped developed six times more dead wood than trees that were pruned differently, and they eventually required more annual maintenance in removing decayed wood. Topped trees don’t form barriers to decay in a way that correctly pruned trees do. Gilman and Knox determined that topped trees had decay reaching back to two and a half feet through the branch below the cuts.
One reason often given for employing topping is that without it, the flowering would fall off. This may have been true with older varieties, but modern hybrids have been selected for their blooming potency. In other words, resist the urge to remove all those old, twiggy stalks and seed heads. “If you leave them alone,” Deahl says, “they’re going to flower like crazy.”
Most crape myrtles mutilated by the practice of topping can be restored to a natural shape with method, patience and a good set of lopping shears (and maybe a step ladder).
First, don’t top the tree again or allow others to do so. Second, remove some of the sprouts that grew the previous year — these are easy to see, being slender and bearing last summer’s seedpods. Remove all but three or four on each stub, and allow those that are kept to sprout and grow this season. The object is to leave sprouts that are growing on the outside of the tree so that you promote an open crown. Any new suckers that emerge from the old wound during the growing season should be removed.
Next winter, when the plant is dormant, leave just one or two of the remaining sprouts. By the following growing season, they will have begun to take on the appearance and thickness of a regular branch. In time, the original topping will be virtually invisible, especially when the tree is in leaf.
Another option is to adopt a pruning regime known as pollarding, which maintains a tree at a given height permanently. Optimally, this is done with young trees — three years after planting or so — once the desired plant structure and height has been attained. At that point, the tree is topped. In a pollarded tree, all the sprouts of the previous year are removed to their base each winter. This permits the tree to develop knobbly structures called pollard heads, which form natural defenses against wound decay.
Pollarding is a common technique applied to street trees in Europe as a way to keep their top growth in check. One of the most conspicuous displays of pollarded Natchez crape myrtles is at the National Gallery of Art’s Sculpture Garden on the Mall. Here, more than 20 have been pollarded every winter to reduce the canopy. The pollard heads are now the size of softballs, or larger.
You can convert a topped tree into a pollarded tree, but this is viable only on young crape myrtles whose trunks are no more than three inches across, and preferably smaller.
Another option for a butchered tree with decay is to cut it to the ground — actually, an inch or two above the soil line but no higher: No stubs, please. From the established root system, new shoots will return with vigor. After a couple of years, the tree can be pruned to leave a desired structure of five or so upright stems that leave an open center and pleasant silhouette. If it is a Natchez, it will still grow to 30 feet after two decades or so.
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