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Heat Wave

July 26, 2011


The term usually makes many people think of the tropics or the desert.

But extreme heat has hit many areas hard so far this summer. Record highs have been broken in some cities, while others have seen their hottest temperatures since the 1980s.

Torrid triple-digit heat roasted parts of the Great Lakes, Ohio Valley and Northeast this past week. Even in late July, reaching temperatures in the 100s certainly isn't the norm in these parts of the country as they are in the Desert Southwest or Texas.

And increased humidity and mugginess make temperatures seem higher than they actually are.

Very hot weather not only puts stress on people, but also on our trees.

Dave Madden, a Davey Tree Expert Company arborist based in Austin, Texas, says in drought-stricken areas, "subsoil moisture is completely gone," and "the trees are losing water faster than they can replace it."

Symptoms of drought stress include wilting and yellowing of foliage. Fertilizing with slow-release nitrogen can help. Tree in right foreground was not fertilized; tree in left background was.

When this happens, trees can be prone to showing signs of drought stress, which include wilted foliage, leaf scorch, sparse canopy, undersized leaves, yellowing, leaf drop or premature fall color. A closer look might reveal stunted twig and bud growth. A drought can even curb a tree's growth for several seasons, even when followed by years of adequate hydration.

On top of the problem of insufficient water, drought-affected trees are more susceptible to insects and diseases.

"Lack of rain, wind and extreme temperatures contribute to tree stress," says Jack Swayze, a district manager with Davey, based in Houston, Texas. "Secondary problems then set in. We've seen extreme numbers of large limbs drop, brittle with loss of water."

Because trees are valuable landscape assets, providing numerous benefits, we don't want to let dry soil conditions reduce their life spans. There are some measures we can take to help our trees

First, water appropriately. Most of a tree's active roots are within the top 12 inches of soil, so they lose water fairly quickly. Be aware of and follow water use restrictions that may apply to your area.

Removing dead and dying branches helps deter bark beetles and other wood-boring insects and enables tree roots to sustain the rest of the tree more efficiently.

And fertilization with 100-percent slow-release nitrogen can reduce severity of drought injury and enable trees to recover more quickly. This is because fertilizer enhances root development, and an expanded root system supplies more water to the tree. Fertilizer also promotes carbohydrate production, which supplies energy necessary for growth.

As hot, hot, hot temperatures continue through the late summer months and sweat beads up on your brow, remember to keep yourself and your trees hydrated. A little liquid and some TLC can get us all through this heat spell more safely.


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