Current Dry Spell Pushing Some Landscape Trees ‘Over the Edge’

First posted on 08-10-2010

By Mary Hightower, U of A Division of Agriculture

A prolonged hot, dry spell may be pushing some landscape trees closer to their demise, said Jon Barry, extension forester for the University of Arkansas Division of Agriculture.

Some trees have suffered through a string of dry summers even last year’s wet summer hadn’t done much to relieve the stress of the dry summers, Barry said.

The National Weather Service has forecast between a 20-40 percent chance of rain through Saturday as a front slides southward into Arkansas.

“Many trees have already been damaged beyond repair,” he said. “A return to normal rainfall might prolong a stressed tree’s life a little, but many trees have already started dying and nothing will reverse that process.”

“For the last several years we have been getting calls about quite a few yard trees dying,” he said. “Most of these trees are large old trees that probably were under stress already, so a string of stressful years has given them that last shove over the edge.”

Barry said yard trees face handicaps their wild cousins don’t.

“One of the reasons yard trees are so vulnerable to drought stress, is that they often do not have enough room to develop a good root system,” he said. “Houses, driveways, and sidewalks create dry zones in the soil.

“The few tree roots that might be in these dry zones cannot provide any water to the tree,” Barry said, adding that yard trees often have an abnormally large crown that creates a larger demand for water.

“The restricted volume of soil available for rooting reduces the water available to a tree that already has a king-size thirst, he said.

The first of the 100-degree days started in June in some parts of Arkansas, according to the National Weather Service.

The drought stress is showing as some trees are turning their fall colors and shedding leaves.

“If leaf colors are changing as they would in the fall, and the leaves are dropping, that means the tree is going dormant,” Barry said. “Normally they would do that in the fall in response to longer nights, but they will also go dormant due to drought stress. Dropping leaves dramatically reduces water consumption.”

Barry said that response also shuts down photosynthesis.

“That means the tree may not make any more food this summer, unless it begins to rain and the tree puts out new leaves,” he said. “During the summer, food is normally made in the leaves and stored in the roots so the tree can produce new leaves and flowers next spring.

“Trees can usually survive one or two summers of going dormant early, but too many will kill the tree,” he said.

According The Arkansas Forestry Commission, the wildfire risk as of Wednesday was high in seven counties: Columbia, Hempstead, Lafayette, Miller, Nevada, Ouachita and Union; and moderate in 42 counties: Ashley, Chicot, Clark, Cleburne, Cleveland, Conway, Crawford, Dallas, Desha, Faulkner, Franklin, Fulton, Garland, Grant, Hot Spring, Howard, Independence, Izard, Jefferson, Johnson, Lawrence, Lincoln, Little River, Logan, Montgomery, Perry, Pike, Polk, Pope, Pulaski Sharp, Randolph, Saline, Scott, Sebastian, Sevier, Van Buren, White and Yell counties. The wildfire risk is low in the remaining counties.

Burn bans have been declared in 20 counties: Ashley, Chicot, Columbia, Conway, Falkner, Fulton, Garland, Jefferson, Johnson, Lafayette, Monroe, Ouachita, Phillips, Polk, Pope, Prairie, Sharp, Searcy, Van Buren and White counties as prolonged hot weather continues to dry out trees and increase dry leaf litter.

Wildfires were reported Wednesday near the Prairie-Lonoke county line and on Monday in Pulaski County.

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