The hot and dry conditions that have persisted over much of the state this summer are leaving many trees severely drought stressed and in need of a good watering. The Forest Resources Division of the Michigan Department of Natural Resources (DNR) today reminded residents that it is important to provide supplemental watering to help get these trees through the remainder of the summer and fall.
“Drought stress might not kill trees outright, but it weakens them and makes them more susceptible to other problems such as winter injury or secondary disease and insect problems later,” said DNR Urban and Community Forestry Manager Kevin Sayers. “It’s important to recognize some common symptoms of drought stress on trees and how to provide needed care. Being proactive with watering will help ensure these trees survive until adequate rainfall returns.”
Sayers provided the following examples of drought-stress symptoms, and some dos and don’ts for watering trees.
Symptoms of drought stress: In deciduous trees, leaves may curl or droop, turn brown at the margins (scorching), fall prematurely and exhibit early-autumn coloration. In evergreen trees, needles may turn to yellow, red and eventually brown. In severe or prolonged droughts, leaves may drop prematurely or become brown and remain attached. Twigs or entire branches may experience dieback.
When watering trees, do: Prioritize the plants that need watering first and most often. Newly planted trees should be a priority, as should high-value trees. Provide long, slow soakings to saturate the soil. Water newly planted trees weekly and established trees every two to three weeks. Water under the tree’s dripline (from the trunk, to edge of the tree canopy). Provide 1 inch of irrigation per week (depending on recent rainfall) using the following methods: Sprinkler: Place an empty container or rain gauge nearby to measure about 1 inch of irrigation. Hand watering via hose: Let water run slowly until the ground is saturated (10 to 12 inches deep) and moist near the base of small trees or at various points under the dripline of large trees. Five-gallon bucket: Most newly planted trees need 5 to 10 gallons of water per inch of trunk diameter (at knee height) each week. Soaker or trickle hoses: Saturate the soil under the dripline to at least 10 to 12 inches deep Use mulch to help retain soil moisture and save water. Apply 3 to 4 inches of organic mulch under the tree canopy, but not touching the trunk.
Don’t: Water during the middle of the day. Most of the water applied at the hottest and most windy time of day is immediately lost to evaporation. Use mist sprinklers. As much as 70 percent of water may be lost to evaporation into the air. Water frequently and lightly. This may help the lawn stay green but is ineffective for most trees. Use fertilizer. Fertilizer salts can cause root injury when soil moisture is limited.
