Water shade trees to avoid drought stress

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Kansas City, Mo. -- Trees are stressed by long-term drought and the current triple-digit heat wave, say foresters for the Missouri Department of Conservation (MDC). In the urban forest, where valuable trees shade homes, lawns and businesses, watering them now can prevent losing a tree.

Some trees are dropping leaves to reduce water usage, said Wendy Sangster, an MDC urban forester in Kansas City. That doesn’t mean they are dying. But it does mean they are thirsty. Giving a valued tree a drink is a step to help them stay healthy.

“The best advice is to avoid stress on a tree,” Sangster said.

Drought-stressed trees are more susceptible to damage by disease and insects. Foresters this spring inspected some trees that showed signs of problems due to last summer’s drought and the relatively dry winter.

Now, much of western Missouri is listed on the U.S. Drought Monitor as suffering from moderate to severe drought, based on rainfall and soil moisture readings.

Native trees are adapted to the Midland’s climate swings, and many tree species can survive drought conditions without help. But if a tree in a lawn setting is highly valued for the cooling shade provided, watering it reduces the chances for problems with that individual tree.

Water-loving trees such as hackberry, cottonwood and sycamore are among the first to show signs of drought stress, said Lonnie Messbarger, an MDC resource forester in St. Joseph.

“We’ve seen some fall colors in some, and they’re thinning themselves out and dropping some leaves,” Messbarger said. “It reduces their water usages.”

Don’t give up on a tree that has lost all its leaves, Sangster said. It may have gone dormant. Some species will regrow leaves if watered or if rains return.

Non-native trees or native trees planted near homes away from their normal environment may be more susceptible to drought. Any recently planted trees will especially need frequent watering to survive.

Some watering tips for trees:

  • Water during the hours between dusk and dawn. The soil needs to be moist six to 12 inches deep. Water until a screwdriver can be poked into the ground easily. If possible, water from the trunk to the drip line where the longest limbs end.
  • Large shade trees can be difficult and expensive to water. Messbarger suggests letting water slowly run from a hose or soaker hose under just a section of the tree. Some moisture will help the whole tree. Every few days, move the hose and provide a drink to a different part of the tree’s root system. Complete a watering circle around the tree about every two weeks.
  • A weekly watering will help some drought-sensitive trees until conditions improve, especially if extreme heat and low soil moisture levels continue.
  • Cracks in the soil add to drought stress for trees, Messbarger said. Cracks allow air to reach the roots and subsoil and dry them out. Take a shovel and close the tops of soil cracks to help protect root systems.

For more information, visit http://mdc.mo.gov/landwater-care/homeowners/backyard-tree-care/drought-stress-trees. A related video is available at http://www.youtube.com/watch?v=0yhlq_25BD0.