Jul 07 2011

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Taking care of your landscape trees

By Dennis Smith

Trees in home landscapes are large investment.  A healthy tree increases in value with age; paying big dividends, increasing property values, beautifying our surroundings, purifying our air, saving energy by providing cooling shade from summer’s heat and protection from winters wind.
No doubt the toughest question county agents, foresters and landscape managers receive from homeowners is “My tree looks like it is dying…. What can I do to save it?”  This question often comes after noticing that most of the leaves have turned brown.  Probably too late for any help, except a miracle.
According to Texas Forest Service entomologist, Mr. Jose Pace, homeowners may be “at the mercy of nature” in saving trees from the driest seven-month stretch recorded in Texas history.  The best thing homeowners can do is water trees on our property if possible.
Drought stress is one of the major causes of death of large oak trees.  According to plant pathologist, the stress could be from several years earlier.  Getting an exact cause of death of a tree can be difficult.
Pace said that if the drought doesn’t get the trees, fungus and insects that are attracted to drought-stressed trees can take down the greenery.  The unfavorable conditions could also affect the future growth of trees that survive.
Dehydrated pine trees can also be susceptible to increased activity from pine beetles, which arrive during significant drought periods.
Tree inspection is an evaluation tool to call attention to any change in the tree’s health, before the problem becomes too serious. During the inspection, be sure to examine four characteristics of tree vigor: new leaves or buds, leaf size, twig growth, and crown dieback.
Mulching can reduce environmental stress by providing trees with a stable root environment that is cooler and contains more moisture than the surrounding soil. Mulch can also prevent mechanical damage by keeping lawnmowers and weed trimmers away from the tree’s base. Further, mulch reduces competition from surrounding weeds and turf.
An organic mulch layer of two to four inches of loosely packed shredded leaves, pine straw, peat moss, or composted wood chips is adequate. Plastic should not be used because it interferes with the exchange of gases between soil and air, which inhibits root growth. Care should be taken not to cover the actual trunk of the tree.
Mature trees making satisfactory growth may not require fertilization. Mature trees have expansive root systems that extend from two to three times the size of the leaf canopy. A major portion of actively growing roots are located outside the tree’s drip line.
Some lawn fertilizers contain weed and feed formulations that are harmful to your trees. The same herbicide that kills broadleaf weeds in your lawn is picked up by tree roots and can harm or kill your trees if applied incorrectly.
Trees do not need to be watered every day or even every week.  Normally a bi-weekly watering should provide sufficient water as long as the watering soaks the drip area of the tree.  Apply water at the tree’s drip-line, not at the trunk.
Soil soakers are a good option for watering trees.  Soakers almost need to be left running overnight to adequately water a large tree.  A garden sprinkler is another good choice provided the water is applied slowly so it soaks in rather than running off.  Lawn irrigation typically has little impact on large trees.  Proper lawn irrigation maintains enough moisture in the upper 5 to 6  inches of soil to keep the turf green and growing, but  it provides little water to tree roots, especially during hot dry summer weather.
You can test your watering depth by sticking a metal rod into the soil.  If watered properly, the soil should be moist at least 12 to 15 inches deep.
Although tree removal is a last resort, there are circumstances when it is necessary.

Dennis Smith can be contacted at the Gregg County Extension Office by e-mail at dg-smith@tamu.edu or telephone at: 903-236-8429.

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