Archive | February 2015

Structural pruning improves the longterm stability and health of trees

ice on contorted willow

A corkscrew willow with flexible limbs that easily accommodate the ice without snapping.

Punxsutawney Phil was right: six more weeks of winter. Just when I was putting the finishing touches on a blog entry regarding winter annual weeds, the henbit, chickweed and wild garlic quietly disappeared beneath a blanket of ice yesterday.

The shrubs and trees weren’t so lucky. Some of them looked like reluctant contortionists bent into painful shapes. Those whose branches refused to bend simply broke beneath the weight of the ice.

Unlike snow, which can be brushed off without damaging the limbs, ice requires a hands-off approach. Be patient and do nothing; allow the ice to melt naturally.

For trees the best defense against storms is a strong, weather-resistant crown and trunk. This can only be achieved with structural pruning for the first 15 to 20 years of a tree’s life. That’s right: 15 to 20 years. Like raising a child to adulthood, a young tree must be structurally pruned to develop a pyramidal form with a dominant central leader. Smaller branches must be distributed vertically and horizontally around it. Codominant stems of equal diameter must be removed or subordinated (pruned to supress their growth and eventually removed) because they are often poorly attached as evidenced by the included bark; they split apart like wishbones during ice-and windstorms.

loblooyunderice

A contorted loblolly pine (sadly, the contortion is due to ice accumulation and not genetics).

Structural pruning develops a framework of well-spaced, strongly attached limbs. These biomechanically sound trees reach middle-age and are less likely to burden you with costly tree failures.

Ideally, structural pruning begins in the nursery and continues in your landscape. Individual branches should be spaced around the trunk and not clustered together at one point. Single branches create strong attachments with the trunk: as the branch and trunk grow radially (produce annual growth rings), wood from the branch and trunk overlap. Over time the branch looks like a threaded dowel that was screwed into the trunk.

Oftentimes you’ll see a swollen area at the base of limb: this branch collar results from the overlapping of branch and trunk tissues, which indicates a strongly attached branch.Most importantly, the collar houses a natural protective region called the branch protection zone. This unique zone of cells, which develops at the base of the branch and extends into the trunk, resists the invasion of decay-causing organisms into the trunk when the branch dies or is removed—providing that the branch was removed just outside of the collar. Remember this: the branch protection zone develops on individual branches that are less than one-half the diameter of the parent stem which are also less likely to break-away from the parent stem.

Finally, you need to know that pruning creates wounds. The openings created by the removal of branches seal more rapidly on small diameter branches than large ones. So, if you experience empowerment and gratification from sawing through large, hefty branches, consider pruning dead trees.

Despite the woodchuck’s dire forecast, I trust that our winter will be interspersed with brief warm spells. During the next spate of warm temperatures, go outside and examine your living investments. Think about structurally pruning your dormant trees to improve their strength, health, and longevity.

© 2015 Bob Polomski

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Wild garlic are blemishes in the winter lawn.

Wild garlic and wild onion are two common lawn and garden weeds that are a lot like teenage acne:  they appear where you don’t want them and, in some folks, cause lots of anxiety and concern.  At this time of year these weeds look like green splotches on the beautiful brown canvas of dormant centipede and bermudagrass lawns.wild garlic 1

Wild garlic (Allium vineale) is a herbaceous bulb that was probably introduced to the U.S. from Europe by early settlers in the early 1700s.  This cool-season weed appears in the fall and matures and dies down in late spring.  Wild garlic reproduces primarily by above- and below-ground bulbs.

Wild onion (A. canadense) is not as common as wild garlic in our state.  Unlike wild garlic which has hollow leaves and greenish-white flowers, wild onion has flat, solid leaves and pink flowers.
wild garlic 2
Wild garlic and wild onion pose no harm to your lawn.  However, you may find it unsightly.  If these weeds have invaded your landscape, there are a few things you can do.
1.  Do nothing.  Once your dormant lawn turns green and the wild garlic and wild onion begin to dieback, you will forget about them until next fall when they will reappear.  Some people feel uncomfortable with the “do nothing” approach.  In fact, they feel as if something should be done for the neighbors’ sake.  O.k., then, here’s what you do.  Since wild garlic looks so much like cultivated onions, tell your neighbors that you’re growing fancy French scallions in your lawn.  Yeah, tell them that they make their best growth in the lawn, especially when they’re planted in random, haphazard rows .  Who knows, maybe a neighbor or two will believe you.

2.  Spray-paint the wild garlic brown to match the color of your dormant lawn.  Hey, if women can get away with using cosmetics to hide a few blemishes on their faces, you should be able to camouflage the clumps of wild garlic in your lawn.
3.  Pull them out by hand.  Pick a day when the soil has been moistened by a nice, soaking rain.  With a flat-headed screwdriver, loosen up the soil around a clump of wild garlic.  Then, grab the base of the weed and slowly tease it out of the ground.  Since wild garlic produces a bunch of underground bulblets, try to lift them all of them out.  I do it bare-handed because I love the heavenly aroma of garlic.
4.  Apply a herbicide.  Wild garlic is difficult to control with herbicides because it produces several bulblets that do not sprout all at once.  Some bulblets will sprout one year and others will not emerge until the following year; therefore, it can take 2 or 3 years for a postemergence herbicide to control the entire plant.  An effective herbicide for controlling wild garlic and wild onion are the “three-way” types that contain 2,4-D, MCPP, and dicamba (such as, Weed-B-Gon® and Trimec®).  Treat wild garlic and wild onion now–in late November to December, which is when they’re most susceptible to herbicide applications.

If necessary, make a followup application in late February or early March.  Please read and follow the label directions when using any pesticide.

If wild onions and wild garlic are growing in your flower borders or among your azaleas and other shrubs, refer to approach #3.
Fortunately, we’ll lose sight of wild garlic and wild onion in late Spring.  At that time, no one will know if you accepted or got rid of these blemishes.

Be kind to your crepes

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Crepemyrtle before pruning. Credit: Paul Thompson, Clemson Extension.

Have you pruned your crepemyrtles yet? No, I didn’t ask: have you cut them into broomsticks or hat racks? Have you pruned them? Did you maintain a vase-shaped form with arching, outward-growing branches? If you cut the trunks back to an arbitrary height, then you committed “crepemurder.” The large open-faced wounds that result from this mutilation do not “heal” or callus over rapidly. They provide entry points for fungal organisms that can infect and kill limbs and trunks. The butchered crepemyrtle doesn’t die immediately; a few parts die over a period of time–a limb here and a trunk there. Eventually, the hatracked crepemyrtle looks so miserable that it begs to be pruned at soil level.

If you perpetrated crepemurder in the past, atone for your actions now. The first step to properly pruning a crepemyrtle involves removing any broken, dead, and diseased limbs.

The next step is to stop, step back, and look. Imagine a vase-shaped tree with arching branches that flow outwards. Visualize those long, sun-drenched limbs bearing 6- to 12-inch long clusters of flowers in the summer.

C2_crapemyrtle-after

Crepemyrtle after pruning. Credit: Paul Thompson, Clemson Extension.

Now begin pruning. With a sharp pair of loppers or pruning shears, start at the bottom and work up.  Remove any suckers sprouting from the base of your crepemyrtle.  Also, thin out any side branches from the lower third of the trunk to expose the attractive bark.  Thinning refers to the removal of entire shoots or limbs back to their branch points–the point of attachment of a branch to the trunk or limb.

Now work your way to the top. Thin-out any inward-growing branches. With the center of your crepemyrtle opened up to sunlight, focus your attention on rebuilding the structural framework of your tree. If you headed-back or topped your crepemyrtle last spring, you destroyed its structure. Bunches of spindly shoots emerged from nooks and crannies around and below the cuts. Keep a few of the thick, well-attached outward-growing shoots and remove the rest. As you selectively thin-out the top, visualize the space occupied by the remaining structural limbs. Imagine a fountain-like canopy with limbs that rise upwards and arch outwards. Finally, head-back or tip-prune any wayward or unbranched limbs to make them fuller-looking.

Now your pruned crepemyrtle should appear treelike instead of like a collection of sawed-off broom handles. But wait–you’re not done yet. When it starts leafing out, come back a few times in the spring and early summer to fine-tune its framework. Pinch out any green shoots growing in the wrong direction and thin out any shoots you had missed earlier. By midsummer your crepemyrtle should come close to looking like the image you had in mind in midwinter.

Pruning crapemyrtles the right way this winter takes a little bit of skill and a whole lot of patience. But the rewards this summer will be priceless.