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PRUNING PRINCIPLES

Looking around East Texas this year, you will no doubt see trees that are pruned in several ways. How a tree is pruned will greatly affect the growth form, vigor, and stability of the tree. Two common types of pruning are thinning out and topping. Topping is not a recommended practice. In fact, some refer to it as "the Texas Chain Saw Massacre."

Thinning out is also known as selective cutting or drop-crotching. It involves complete removal of a branch back to the main stem or to another lateral branch to the point of origin. Thinning conforms to the tree's natural branching habit and results in a more open tree, emphasizing the branch's internal structure. Thinning also strengthens the tree by forcing diameter growth of the remaining branches.

Topping is a more severe type of pruning and consists of cutting the top of a tree in a "flat-top" or "snowball-cone" shape. With topping, effects will be far more negative. Numerous new shoots will develop rapidly, producing many fast-growing, succulent sprouts. The tree will appear bushy, and the new shoots will generally form more structurally weak junctures with the main branch of the limb. Branches will tend to angle up very closely to the tree trunk, producing weak crotches. Topping trees vastly reduces the number of leaves they have, thereby limiting the trees' ability to produce food energy through photosynthesis. This, in turn, can make them susceptible to attack by insects and disease. It can result in early death. In addition, topping produces large pruning cuts that are slower to heal and more vulnerable to decay.

An ideal ornamental tree shape is a straight tapered trunk with scaffold branches coming from the trunk. The most structurally sound branches are those that come out at wide angles from the trunk. By keeping in mind a general structural framework for trees that encourages strong growth, the trees will be better able to withstand adverse weather and environment conditions.

Linda Billings, Smith County Master Gardener
Texas AgriLife Extension Service


PRUNING TIPS

The way you prune a plant influences how it will look, both now and in the future. Where you make a cut will determine whether new shoots appear and which direction they will grow. If you want to remove a cross limb or any other branch that should not grow back, cut it at its point of origin, leaving as little stub as possible. Anytime you cut a branch in the middle, you encourage new shoots.

Study a branch before cutting. It will have either leaves that alternate from one side of the branch to the other or leaves that are paired along the branch. At the base of every leaf is a dormant bud. Wherever you prune, a new shoot will sprout from the leaf just below the cut. If your plant has alternate leaves, cut just above a bud that points in the direction you want it to grow. Dormant buds are found at the base of every leaf, and these buds will sprout when the tip of the branch is pruned.

Shearing is also a type of pruning that maintains a tree or shrub in a formal shape, such as a hedge or topiary plant. Most plants should be maintained in their natural form. You should do your last pruning or shearing of the season several weeks before the first frost so the plants have time to put on new growth that will hide the cut leaves. Shearing too late will prompt succulent new growth that will be killed by frost.

Also, be sure to shape a hedge so that it is slightly wider at the base than at the top. This allows sunlight to reach the lower branches, maintaining a good thick growth. If the top is as wide as or wider than the bottom, it will shade the lower portion and the hedge will become bare at the base.

Note: If you need to prune azaleas or camellias, do so by the end of May because they start setting next year’s buds soon after this.

Sandra Kurtz, Smith County Master Gardener
Texas AgriLife Extension Service


PRUNING FLOWERING TREES AND SHRUBS

When is the best time to prune flowering trees and shrubs? The answer depends on whether the plant produces flowers on old (last year's) or new (this year's) growth. The following information on pruning comes mainly from two internet sources:

http://gardening.about.com/od/treesshrubs/a/PruneTreeShrubs.htm

http://www.hintsandthings.co.uk/garden/pruning.htm

And before I begin, let me say right up front that far too many gardeners in east Texas perform "Crepe Murder", which is the cutting of crepe myrtles back to main trunks every fall. This practice causes the plant to have fewer blossoms in the spring, makes a strange looking if not downright ugly plant, and causes spindly new growth each spring. Like other trees, crepe myrtles should be pruned only by selectively cutting out whole branches to maintain the shape of the plant. If a plant is too big for the space, take it up and plant one of the many varieties of a more appropriate size.

As for trees, no tree should be "topped" which is the cutting back of major limbs leaving several feet of the limb sticking out beyond the trunk. Trees don't recover from this radical procedure, and they never bush back out attractively. As with crepe myrtles, trees should be pruned by selectively cutting out limbs back to a major node. Trees should only be pruned to maintain shape (not size), to remove dead or diseased wood, or to keep limbs from contacting structures.

So, with that said, some trees and shrubs benefit from annual pruning. It keeps them in shape, gets rid of dead and diseased wood and encourages new growth. But timing is important, especially for the ones that flower.

Early spring bloomers set their flower buds the fall before. Pruning them early in the spring would mean losing some blossoms. Most of the time this is not what you want. However there are exceptions. It’s often easier to prune when you can see the shape of the plant, before the branches are masked by leaves. Trees and shrubs that are in need of a good shaping could sacrifice a few blooms to be invigorated by a spring pruning.

The most important reason for pruning flowering shrubs, and to a lesser extent trees, is to maintain a large portion of the plant as young, vigorous wood. Since most flower buds are formed on current or previous year's growth, you can remove up to one third of the oldest wood annually to keep the plant vigorous. Such pruning will stimulate future flower and fruit development. Many flowering plants, such as azaleas, produce more flowers if old flowers and fruit clusters are removed.

In general, here are some rules for pruning:

  • Prune flowering shrubs that bloom in spring, within a month after flowering.
  • Prune summer flowering shrubs between January and March, before new growth starts.
  • To keep a base of a hedge leafy, cut into a pyramid shape in spring, so that the top is narrower than the base. If a hedge is pruned wider at the top than the bottom the lower part will be shaded and the foliage will fall off allowing the top growth to spread, compounding the problem.
  • If a hedge is too dense, cut it back to the main stems on one side only. Let the hedge recover and produce new growth for a year, then cut back the other side.
  • If the hedge has become too tall, cut back every second shrub to within a few inches of the ground. New shoots should sprout around the severed trunks. Cut back the remaining shrubs the following year.
  • Privet, Holly, Berberis, Forsythia, Roses and Spiraeas respond well to hard pruning.
  • For climbers that flower on new growth, e.g. Buddleia, Clematis Jackmanii, winter pruning is best.
  • For climbers that flower on previous year's growth, e.g. early flowering Jasmine, Forsythia, Honeysuckle and ornamental Quince, prune after flowering.
  • February is the best time to prune hybrid tea and floribunda roses. Cut out dead, diseased or thin wood and trim back the main shoots. When cutting back main shoots count buds from base of each shoot and cut just above the second or third one. The length of the shoot is less important than the number of buds.
  • Shrub roses are best pruned in winter. As both old and modern roses produce most of their flowers on shoots produced from old wood, prune lightly. Remove dead, thin and decayed wood, and shorten main stems by about one third.
  • Rambling roses should probably be pruned after spring/early summer bloom. Cut untidy, flowered shoots right down to the base and tie new shoots to the trellis or support. If there are only a few new shoots, leave some of the flowered shoots in place cutting back just a little.
  • Climbing roses are also best pruned after spring/early summer bloom. Remove any crossing or thin shoots and reduce the height of the main stems by about one third. Remove any side shoots that spoil the shape and cut back the others by about two thirds.
  • Miniature roses should be pruned in February. Cut off any dead, diseased or thin wood and trim back the main stems to about one third of their length.

In general, for east Texas, the following are guidelines for pruning:
    Prune in late spring/summer soon after bloom.

  • Azalea (Rhododendron species)
  • Beautybush (Kolkwitzia amabilis)
  • Bridal Wreath Spirea (Spirea x vanhouttei)
  • Forsythia (forsythia x intermedia)
  • Hawthorn (Crataegus species and cultivars)
  • Hydrangea, Bigleaf (Hydrangea macrophylla)
  • Mockorange (Philadelphus coronarius)
    Prune in winter or early spring while dormant, but prune only for shape as too much taken off will affect next season's blooms.
  • Butterfly Bush (Buddleia davidii)
  • Crape Myrtle (Lagerstroemia indica)
  • Flowering Plum (Prunus blireana)
  • Glossy Abelia (Abelia x grandiflora)
  • Honeysuckle (Lonicera fragrantissiam)
  • Hydrangea, Peegee (Hydrangea paniculata ‘Grandiflora’)
  • Potentilla (Potentilla fruticosa)
  • Spirea (except Bridal Wreath) (Spirea japonica)
  • Wisteria (Wistera species)
Mary Hamlin, Smith County Master Gardener
Texas AgriLife Extension Service
PRUNING YOUNG PLUM TREES

The plum tree you planted last year survived. Now What? If your tree grew vigorously last year it may be time to prune it. Plum trees should be pruned in the late winter, just before the bud breaks. Open center pruning is recommended for stone fruit trees and should be done when the tree is 1 to 3 years old. Large branches that fill the center of the tree should be removed. This will leave a "bowl like center". Be sure to leave enough branches in the center of the tree to provide some leafy growth, which will provide a bit of shade to prevent sunscald. Vigorous upright shoots should also be removed. Light pruning may be done at any time during the year. The same rules also apply to peaches.

Debrah Golden, Smith County Master Gardener
Texas AgriLife Extension Service


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