Seattle residents cherish their trees. From iconic Douglas firs to majestic maples, our urban canopy is a vital part of what makes this city so livable. Yet, as summers grow hotter and drier, trees face unprecedented stress. It’s essential to take proactive measures to help our trees withstand the dry season to ensure Seattle remains lush and green.
Recent climate patterns have brought more frequent and intense dry spells to the Pacific Northwest. During these periods, trees can suffer from dehydration, weakening health and increased susceptibility to pests and diseases, so providing them with consistent and proper tree care annually and during the dry season is crucial.
Some common symptoms of trees in dry conditions include:
- Curling or wilting leaves.
- Scorched leaves.
- Leaf drop or a thinning canopy.
- Dying branches.
- Increased susceptibility to wood-boring insects.
- Discoloration of conifer tree needles (grayish green to rust).
At The Davey Tree Expert Company, ISA Certified Arborists located in Redmond, Lake Forest Park, Tacoma and the surrounding areas are available to help with your dry-season and watering maintenance
How to reduce heat stress on trees
“The most effective way to support trees during dry weather is through preventive annual maintenance, like deep watering, proper mulching, pruning dead limbs and overgrown canopies and soil applications of humates and phosphites,” says Jason Hayes from The Davey Tree Expert Company.
Tree-watering tips
Follow this advice from Hayes for successful deep watering during the dry season:
- Water slowly. Use a soaker hose or a drip irrigation system to deliver water slowly and steadily. This method allows water to penetrate deeply into the soil without runoff.
- Water infrequently. Instead of daily watering, aim for a thorough soaking once or twice per week. This encourages deeper root growth, making trees more resilient to drought.
- Water in the morning. Water early in the morning to reduce evaporation losses and ensure trees have ample moisture to face the day’s heat.
“Mulching is another critical technique to help trees retain moisture,” says Hayes. “A layer of mulch, such as wood chips or bark, applied around the base of the tree can significantly reduce water evaporation, moderate soil temperature and improve soil health. Just be sure not to volcano mulch!”
Proper mulching tips
Hayes’s tips for proper mulching:
- Proper application. Spread mulch in a 3- to 4-inch layer, extending to the tree’s drip line.
- Avoid volcano mulching. Do not pile mulch in a volcano form against the trunk. This can cause rot and pest problems. Instead, leave a 1-inch space between the mulch and the trunk.
- Refresh regularly. Replenish mulch as needed, at least annually and if necessary after heavy rains or wind. This maintains its effectiveness in conserving soil moisture.
In addition to regular watering and proper mulching, trees can benefit from extra care during unexpected heat waves. When temperatures soar, trees need protection, too.
- Humates. Humates help improve microbial activity and nutrient absorption for your tree. They also improve water distribution and retention so the soil can hold more water from irrigation. Humate products may also include wetting agents and micronutrients to boost these benefits.
- Phosphites. Phosphites stimulate trees’ natural defenses against heat and drought stress, helping them to conserve water. Phosphite products include potassium, which also helps trees to maintain moisture uptake and manage stress.
- Tree pruning and trimming. Pruning dead limbs and overgrown canopies can help reduce the overall amount of water the tree needs. It also improves the overall health of the tree.
- Temporary shade. Shade cloths can provide temporary relief from direct sunlight for young or newly planted trees.
Long-term impacts of heat stress on trees
At high temperatures and without sufficient water, trees eventually reach a point where they can’t take up enough water from the soil to support the whole tree canopy. As temperatures escalate and available water becomes limited, the tree closes stomata on the leaves which results in reduced photosynthesis and slowed growth, which can weaken the tree and make the tree susceptible to tree pests and diseases.
“Caring for our urban forest is not just an individual responsibility but a community effort,” says Hayes. “By adopting these techniques and encouraging our neighbors to do the same, we can collectively ensure the health and longevity of Seattle’s trees.”
Why hire a professional certified arborist?
Professional arborists are knowledgeable about your trees and their needs, as well as trained to handle a variety of tree issues. A certified arborist can do a proper assessment to tell you what it needs, help you retain the value of your home investment, and provide just enough care to give it the boost it needs.
The Davey Tree Expert Company provides research-driven tree services, grounds maintenance and environmental consulting for residential, utility, commercial and environmental partners in the U.S. and Canada.