Record heat, high winds and lack of rain have taken their toll on the trees in many parts of Michigan this year. Almost all the trees in my area are showing signs of stress.

Thinning foliage, light green or early coloration of leaves and/or scorched leaves seem to be the norm. Evergreens are drooping, heavy with cones, another sign of stress.

In periods of drought, a sudden thunderstorm may dump what seems like a large amount of water on the landscape, but when the soil is bone dry, much of it ends up in runoff and fails to permeate the soil.

Many homeowners believe their in-ground irrigation systems provide adequate water for trees as well as turf, but that’s not the case, especially in times of hot weather and drought.

Folks think mature trees develop long roots that collect moisture deep in the ground and don’t need to be watered when the weather turns hot and dry, but in reality the feeder roots, those that take up moisture and nutrients for trees, are concentrated in the upper 12 to 18 inches of soil. Depending on the size, these roots can spread from a few feet to long distances beyond the tree’s drip line, so when watering, it’s key to provide a deep soaking to the entire area beneath the canopy of the tree and, in the case of large trees, several feet beyond.

Since these roots are spread out, just watering next to the trunk is not effective and also may encourage wood rot at the base of the tree.

An easy way to check the moisture level of clay or loam based soils is to poke a long screwdriver into the ground. The tip will easily pass into moist soil so if you can’t penetrate at least 6 inches deep, it’s time to water. Depending on your method of watering, your soil type and the depth of dry soil, it may take an hour or two to get the job done. A single deep soaking is far better than shallow watering a couple of times a week.

Large trees need an inch and a half of water a week. The best way to keep track of what Mother Nature supplies is to use a rain gauge, so you can make up the difference.

Lots of folks stop watering their trees and shrubs after a killing frost, but professionals counsel to monitor the rainfall and keep your trees and shrubs watered until the ground freezes.

Nancy Szerlag is a master gardener and Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to and click on Ask Nancy. You can also read her previous columns at

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