Pruning & Trimming

Pruning & Trimming

Reasons for pruning:
  • To train the plant
  • To maintain plant health
  • To improve the quality of flowers, fruit, foliage, or stems
  • To restrict growth

As a general rule, no more than 25% of the tree should ever be removed from a tree per season. This helps to prevent the tree from going into shock from a very stressful procedure and gives it time to recover before trimming it again.

Plan Approach to Pruning


Pruning should follow a definite plan. Consider the reason or purpose before cutting begins.

By making the pruning cuts in a certain order, the total number of cuts is reduced greatly. The skilled pruner first removes all dead, broken, diseased or problem limbs by cutting them at the point of origin or back to a strong lateral branch or shoot. Often, removing this material opens the canopy sufficiently so that no further pruning is necessary.

The next step in pruning is to make any training cuts needed. By cutting back lateral branches, the tree or shrub is trained to develop a desired shape, to fill in an open area caused by storm or wind damage or to keep it in bounds to fit a given area. To properly train a plant, one should understand its natural growth habit. Always avoid destroying the natural shape or growth habit when pruning unless maintaining a close watch over the plant, for after a period of time it attempts to assume the more natural growth habit.

Make additional corrective cuts to eliminate weak or narrow crotches and remove the less desirable central leader where double leaders occur. After these cuts have been made, stand back and take a look at your work. Are there any other corrective pruning cuts necessary? If the amount of wood removed is considerable, further pruning may need to be delayed a year or so. Remove water sprouts unless needed to fill a hole or to shade a large limb until other branches develop.

When to Prune


Pruning can actually be done at any time of the year; however, recommended times vary with different plants. Contrary to popular belief, pruning at the wrong time of the year does not kill plants, but continual improper pruning results in damaged or weakened plants. Prune when it results in the least damage to the plant. There is little chance of damaging the plant if this rule is followed. In general, the best time to prune most plants is during late winter or early spring before growth begins. The least desirable time is immediately after new growth develops in the spring. A great amount of food stored in roots and stems is used in developing new growth. This food should be replaced by new foliage before it is removed; if not, considerable dwarfing of the plant may occur. This is a common problem encountered in pruning.

It also is advisable to limit the amount of pruning done late in summer as new growth may be encouraged on some plants. This growth may not have sufficient time to harden off before cold weather arrives resulting in cold damage or winter kill. Prune plants damaged by storms or vandalism or ones with dead limbs as soon as possible to avoid additional insect and disease problems that may develop.

Wound Dressing


Much has been written about the advantages and disadvantages of using a wound dressing on large cuts. Traditionally, wound dressing or pruning paint is used only on cuts larger than an inch in diameter. However, scientists have found that wound dressings are strictly cosmetic and have little to do with preventing insect or disease damage to the wound area. Pruning paint may, in fact, slow down the healing process. In general, wound dressings are not recommended or necessary.

Making Pruning Cuts Correctly


To encourage rapid healing of wounds, make all cuts clean and smooth. This requires good, sharp pruning equipment. Do not leave stubs since they are usually where die back occurs. Avoid tearing the bark when removing large branches. The following provides some specifics on pruning techniques.

Most woody plants fall into two categories based on the arrangement of the buds on the twigs and branches. In general, the bud arrangements determine the plants’s typical growth habit. Buds may have an alternate or an opposite arrangement on the twigs. A plant with alternate buds usually is rounded, pyramidal, inverted pyramidal, or columnar in shape. Plants having opposite buds rarely assume any form other than that of a rounded tree or shrub with a rounded crown. The position of the last pair of buds always determines the direction in which the new shoot will grow. Buds on top of the twig probably will grow upward at an angle and to the side on which it is directed. In most instances, it is advisable to cut back each stem to a bud or branch. Selected buds that point to the outside of the plant are more desirable than buds pointing to the inside. By cutting to an outside bud, the new shoots will not grow through the interior of the plants or crisscross.

When cutting back to an intersecting (lateral) branch, choose a branch that forms an angle of no more than 45 degrees with the branch to be removed (Figure 5). Also, the branch that you cut back to should have a diameter of at least half that of the branch to be removed. Make slanting cuts when removing limbs that grow upward; this prevents water from collecting in the cut and expedites healing.

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To “open” a woody plant, prune out some of the center growth and cut back terminals to the buds that point outward. In shortening a branch or twig, cut it back to a side branch and make the cut 1/2 inch above the bud. If the cut is too close to the bud, the bud usually dies. If the cut is too far from the bud, the wood above the bud usually dies, causing dead tips on the end of the branches. When the pruning cut is made, the bud or buds nearest to the cut usually produce the new growing point. When a terminal is removed, the nearest side buds grow much more than they normally would, and the bud nearest the pruning cut becomes the new terminal. If more side branching is desired, remove the tips of all limbs. The strength and vigor of the new shoot is often directly proportioned to the amount that the stem is pruned back since the roots are not reduced. For example, if the deciduous shrub is pruned to 1 foot from the ground, the new growth will be vigorous with few flowers the first year. However, if only the tips of the old growth are removed, most of the previous branches are still there and new growth is shorter and less vigorous. Flowers will be more plentiful although smaller. Thus, if a larger number of small flowers and fruits are desired, prune lightly. If fewer but high quality blooms or fruits are wanted in succeeding years, prune extensively.

Topping Versus Thinning


All too often trees are topped to reduce size or to rejuvenate growth. In either case topping is not a recommended practice; in fact, some refer to it as the “Texas chain saw massacre”. Topping is the process whereby a tree is cut back to a few large branches. After 2 to 3 months, regrowth on a topped tree is vigorous, bushy and upright. Topping seriously affects the tree’s structure and appearance. The weakly attached regrowth can break off during severe wind or rain storms. Topping may also shorten the life of a tree by making it susceptible to attack by insect and disease.

Thinning is a better means of reducing the size of a tree or rejuvenating growth. In contrast to topping, thinning removes unwanted branches by cutting them back to their point of origin. Thinning conforms to the tree’s natural branching habit and results in a more open tree, emphasizing the branches’ internal structure. Thinning also strengthens the tree by forcing diameter growth of the remaining branches.

Pruning Mature Trees


The home gardener should limit pruning of mature trees to smaller branches that can be reached from the ground. Leave the trimming of large branches and work off the ground to professional arborists who are skilled climbers and have proper equipment and insurance. Trees generally require less pruning than other ornamentals in the landscape but may occasionally need corrective pruning to maintain health and vigor. Mature trees are generally pruned only for sanitation, safety or to restrict size. Trees are best pruned during the dormant season. This is especially true for oaks to help prevent the spread of oak wilt.

Pruning Shrubs

Deciduous and Flower Shrubs


Pruning recommendations for most deciduous shrubs consist of thinning out, gradual renewal and rejuvenation pruning. In thinning out, a branch or twig is cut off at its point of origin from either the parent stem or ground level (Figure 8).

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This pruning method results in a more open plant; it does not stimulate excessive new growth, but does allow room for growth of side branches. Considerable growth can be cut off without changing the plant’s natural appearance or growth habit. Plants can be maintained at a given height and width for years by thinning out. This method is best done with hand pruning shears, loppers or a saw, but not with hedge shears. Thin out the oldest and tallest stems first.

In gradual renewal pruning, a few of the oldest and tallest branches are removed at or slightly above ground level on an annual basis (Figure 8). Some thinning may be necessary to shorten long branches or maintain a symmetrical shape.

To rejuvenate an old, overgrown shrub, remove one-third of the oldest, tallest branches at or slightly above ground level before new growth starts.

The general pruning procedure shown for crape myrtle (Figure 9), applies to many large shrubs and small tree species.

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If a shrub is grown for its flowers, time the pruning to minimize disruption of blooming. Spring flowering shrubs bloom on last season’s growth and should be pruned soon after they bloom. This allows for vigorous summertime growth and results in plenty of flower buds the following year.

Some shrubs that bloom after spring usually do so from buds which are formed on shoots that grow the same spring. These shrubs should be pruned in later winter to promote vigorous shoot growth in spring.

Source for Pruning/Trimming: Aggie Horticulture®

Horticulture/Forest Science Building | 2134 TAMU | College Station, TX 77843
Phone: (979) 845-5341 | Fax: (979) 845-0627 |

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Fertilizing

As always, read the label! Make sure the fertilizer you are using contains no herbicide.  Trees and shrubs require two to five pounds of actual Nitrogen annually to be their best. The fertilizer requirements are very similar to turf areas. To calculate how much granular fertilizer you will need to use, look at the fertilizer package. There should be three numbers like 16-16-16, 25-0-2 or something similar. These numbers represent the percentage of Nitrogen, Phosphorus and Potassium contained in the product.   The first number represents the percentage of nitrogen in a pound of the fertilizer blend. Since you want one pound of actual Nitrogen, divide the first number by 100 which will give you the number of pounds product you will put down per 1,000 square feet of area. (e.g. 16 ¸ 100 = 6.25 lbs. or 25 ¸ 100 = 4 lbs.).

How often should you fertilize? We recommend treating your trees and shrubs once in the spring, and again in the fall.  Over-fertilization can lead to reduced flowering, and excessive foliar growth.

Root DamageMechanical Damage

Keep in mind trees root systems extend past the “drip line” of the tree.  Mature trees can suffer when the soil in the root zone is disturbed.  Adding soil over the top of existing roots can also cause damage.  When dealing with mature trees, try to avoid trenching or paving in these areas. If paving must be added in tree root zones, consider using paver stones rather than poured concrete or asphalt.  Pavers allow air and water exchange necessary to support the tree.

Herbicide Damage/Soil Sterilant

Soil residual herbicides, also referred to as “soil sterilants” persist in the soil for an extended period of time.  Never apply herbicides of this type in any area near the drip line of desirable trees.  Keep in mind tree roots grow.  As the tree matures, the roots may grow into a treated area.   Softer pre-emergent products such as Casoron, or Snapshot will reduce weed growth in and around trees without causing harm. As always read the label before applying any pesticide.