First posted on 08-23-2012
Trees all across Missouri are turning brown. Some have dropped their leaves and look dead, but looks can be deceiving. The Missouri Department of Conservation has advice about how to tell if a tree is dead and how to help survivors.
You don’t have to be a professional forester to know that many trees are stressed by this year’s extreme drought and record-breaking heat. Community Forest Supervisor Nick Kuhn notes that some trees began dropping their leaves in June, and brown foliage is visible everywhere you go now. Species particularly likely to be prematurely leafless include maples, yellow poplars, sycamores and cottonwoods. But he says many of these trees will recover.
“Trees are remarkably resilient,” says Kuhn. “They also can respond surprisingly fast to extreme weather. Early leaf drop is an example of that adaptability.”
Kuhn says leaves can be both assets and liabilities to trees. They combine sunlight and air with water and nutrients from the soil to make sugars that nourish the rest of the tree. On that other hand, they create an enormous surface area from which water evaporates. In a drought, water loss through leaves can pose a deadly threat to trees.
“When a tree loses all its leaves, it looks like it’s dying,” says Kuhn. “In fact, the opposite is often true. The tree may be shutting down in response to a bad situation. Leaf drop dramatically reduces a tree’s risk of dehydration. Most of the trees that are brown or leafless now will remain dormant through the winter and leaf out again next spring.”
Kuhn offers tips for telling whether a tree is dead or simply dormant. First, he suggests bending twigs about the size of a pencil. If they are brittle and snap, it might mean parts of the tree have died. If they bend but don’t break with a snap, your tree may still be alive.
Another test to try is to scrape bark away from a small twig using your fingernail. If the tissue under the bark is moist and green, your tree probably is still is alive. You also can break open buds at the ends of twigs by rubbing them between your fingers. If they are moist and green the tree may still be alive.
“The only way to be 100-percent sure if a tree will survive this drought is to wait until next spring and see if it leafs out,” says Kuhn. “In the meantime, there are some things you can do to improve landscape trees’ chances of survival.”
Kuhn recommends slowly soaking the ground under the canopy of the tree. He advises against watering through a pipe stuck into the soil. Most of a tree’s water-absorbing roots are within two feet of the surface. Slow watering over a large area reaches more roots than deep watering in one area.
“Use a soaker hose, sprinkler or drip irrigation system,” Kuhn advises. “For smaller trees, you can poke a few pinholes in empty milk jugs or other large containers and fill them with water so it seeps out slowly. If possible, water from the trunk to outside the drip line past where the longest limbs end.”
Kuhn says trees need about 2 inches of water per week when there is no rain. When using a sprinkler, place several small containers under the canopy of your trees. When the average depth in the containers is about 2 inches, you are done with that tree. You can also probe the soil to a depth of 6 to 8 inches. If the soil is saturated to that depth, then you are done.
“It’s more about watering over the right area and to the right depth than a certain number of gallons,” says Kuhn.
Large shade trees take time to water completely, and while that can be expensive, trees are long-term investments. Watering just one area at a time will still help the whole tree. Move the hose or container every few days to provide a drink to a different part of the tree’s root system.
Newly planted trees are the most susceptible to water stress, so monitor those closely. Mulch helps retain soil moisture. Apply a 3-foot-wide circle of mulch about 3 inches deep, and keep it approximately 3 inches from the trunk. Mulch keeps soil cool and adds nutrients as well.
Cracks in the soil indicate severe soil drying and add to drought stress for trees by allowing air to reach roots and subsoil and dry them out. Mulching or filling soil cracks with additional soil can help. However, simply pushing in the sides of cracked areas can damage surface roots and expose a new layer of soil to sun and wind, creating dryer soil.
For more information on tree care, visit mdc.mo.gov or contact your local MDC office.
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