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Yellow already? Drought stress may turn leaves early

Drought stress can turn leaves early -- and even kill your tree.
Credit: KUSA
Yellow leaves in summer are sometimes indicative of trees that are under stress due to drought.

KUSA — You may be noticing the leaves in your area turning color already and even falling off the trees.

This may be a result of this year’s drought.

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There are several reports of trees in the high country turning color, and falling already, but there is also some concern over urban trees.

A drone flight over Cherry Creek revealed what mostly appears to be a lush green environment, but the signs of drought stress might not yet be visible in the canopies of the trees. The first clue is closer to the roots.

“It’s always good to check the soil moisture, either with a screwdriver or something like that, where you can actually pull up a little soil and see how much moisture’s in it,” said Keith Wood, a community forester with the Colorado State Forest Service. “If it crumbles and it's dry, it’s probably a good indication that tree is drying up and needs some water.”

Wood said that drought stress will be more prevalent in southern Colorado, but trees anywhere that don’t get water from lawn irrigation systems should get watered during long stretches without rain.

“Usually by the time they start showing wilting, and drying leaves from drought stress, it’s too late to turn some of those branches around, and sometimes we can lose the whole tree too, especially if it’s a younger tree without an established root system,” Wood said.

He said that most trees will attempt to manage drought themselves. That waxy coating on the leaves will get a little thicker in times of drought to help retain moisture.

He said the tree could drop some leaves, to save water, and there are also tiny holes on the leaves that intake carbon dioxide. Those can be adjusted by the tree.

“Those close up, and that keeps water in the tree, and helps it through these dry times,” Wood said.

Good rain Monday, and through the rest of the monsoon season, could save the health of the tree, but it may be too late to extend the fall leaf season.

Wood said his expertise is in urban community trees, but said years with drought have usually resulted in an earlier and shorter leaf-viewing season in the Colorado high country.

Seventy-five percent of Colorado remains in drought conditions, with the worst levels in southern Colorado, but most of the high country has been in some level of drought for the entire year.

Wood said there are many reasons, other than drought stress, that could cause leaves to change color, or drop this early in the year.

Below are some links that he recommended to help diagnose tree problems and that show how to water during drought conditions:

Save our Shade

Colorado Tree Coalition

Colorado State Forest Service

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