Sizzling summer temperatures are scorching landscape trees and shrubs, a Utah State University pathologist and a USU forester say.

Many oaks, maples and other trees and shrubs along the foothills are looking sickly now, but Sherm Thomson, USU Extension pathologist, said those trees generally are adapted to Utah's dry summers.Aspens, however, aren't adapted to the dry conditions and often develop black leaves and dead terminals.

"The water available in the soil profile is low, and in many areas the water table is dropping out of reach of the root system," said Thomson.

The result, he said, is commonly called summer leaf scorch. Many broad leaf trees are showing marginal scorching and some leaf death. With some species, leaf drop is common.

And many deciduous trees not native to the Rockies are having trouble this summer, said Fred Baker, Utah State University Extension forester.

"Any tree that's been brought in from another area probably needs more water," Baker said.

The trees apparently cannot transport enough water to maintain the foliage that developed during the moist spring.

"This may be especially true on hot days when the wind is blowing," Thomson said, "and can even happen when there is adequate soil moisture."

When roots of woody plants are unable to take up enough water, they close their stomata, the breathing pores in the leaves, which may occur before symptoms of wilt or scorch are seen.