Tree Care Tips

The continued lack of rain is starting to hurt the trees. Elizabeth Barrett wrote the following advice on how to take care of our local trees. The article originally ran in the Bellevue Civic Newsletter. Thanks to Suzette Lyon for sending me the article.

Large trees are a defining factor in the character of the many neighborhoods and are the most valuable assets to our landscapes. Please help them survive. Most of us know that newly planted trees need regular watering. However, as the extreme heat drags on without any rain for weeks, the older and larger trees are starting to show signs of stress. Tree leaves may wilt, curl at the edges, and turn yellow. In a continued drought, leaves may be smaller than normal, drop prematurely, or remain attached to the tree even though brown. Visually check trees and plants early in the morning — if they are already wilting, they need water immediately.

To help your trees survive the heat and lack of rain, water the lawn under the tree, remembering that the tree roots extend well beyond the tree canopy (leaf area). Large street trees are hard to water directly because the water runs off into the street. If you water your lawn, you will help the tree because its roots likely extend under the sidewalk into the lawn area. Try to guess where the roots are and water that area. You can also trickle water around the trunk and it will follow the roots to some extent.

• Allow water to infiltrate. If it starts puddling or pooling, move the hose around to give time for water to soak in rather than run off. It may take several hours to water a large tree depending on what watering system you have. I have been relying mostly on sprinklers, but pretty much everything I’ve read states that soaker hoses or drip irrigation are more efficient and less wasteful.

• Allow the soil to dry out between waterings. The soil should not stay saturated. Too much water can kill a tree by eliminating the air from the soil and suffocating the roots. To determine when to water, you can use a screwdriver to probe or poke the soil. If it’s extremely hard to penetrate then the soil is very dry.

• Mulch around your trees with 2-3 inches of organic mulch to reduce moisture loss. Pull back mulch 6” from the trunk of the tree. Mulch the entire area under the canopy if possible. Wait for a good soaking rain before mulching.

• Remove dead and weakened branches. Leaving broken, dead, insect-infested or diseased branches can further weaken a tree during drought and set the tree up for deadly problems down the road. Avoid pruning live branches while the tree is under stress as this forces the tree to expend energy to seal the wound.

• Do not fertilize or use herbicides around a tree that is under drought stress.

• Do not dig under the tree canopy because this will reduce the capacity of the tree to uptake water.

Thanks to local arborists Joel Koci of Arborcare and Andy Mason of Arborscapes for their help and tips!