Heat, Drought, and Wildfires Put Stress on Urban Trees

Ft. Collins, CO (July 3, 2012) – With longer stretches of triple-digit heat in many parts of the U.S. and prolonged periods of drought, it’s not just forest and grassland that are in danger from disease and wildfire, urban trees are also being stressed.  And in many places, the boundary between urban areas and forests are precipitously close.

The dangers from wildfire in forested areas on the urban fringe are greater than ever before, as last week’s catastrophic fires in Colorado, and across the U.S., made clear. Current forest conditions, weather patterns and the growing number of homes in interface areas, currently more than 44 million homes and growing, all contribute to the problem.

In many cities there are also water restrictions, making it difficult to keep urban trees adequately watered.  And dry trees are more susceptible to attacks from insect and disease.  To avoid stress on urban trees and potential tree loss, proper watering is required.

The Colorado State Forest Service offers these tips for watering trees without overtaxing the water supply:

  • Water a wide area. Tree root systems, unlike carrots, may spread two to three times wider than the height of the tree, with most absorbing roots in the top foot of soil. Apply water to soak the entire area within the drip line (the critical root zone directly underneath the full span of a tree’s branches).
  • Water slowly. To ensure deep penetration, use a deep root fork (inserted 8 inches or less), soaker hose on low setting or soft spray wand to apply water slowly to the full area within the drip line. Placing a running garden hose against the base of a tree for several minutes is far less effective.
  • Keep the yard green. Trees located in irrigated lawns generally do not require additional water, as long as the area surrounding the tree receives adequate moisture. Conversely, a dry, yellow yard means the roots of any trees present are also dry.
  • Focus on non-irrigated trees. Trees that do not receive water from sprinkler systems or irrigation require additional water. Every week, apply 10 gallons of water for each inch of tree trunk diameter. Water newly planted trees even more frequently; larger trees, which have extensive root systems, can be watered less frequently.
  • Mulch. Mulch is an inexpensive solution to retain soil moisture and save water. Apply 4 inches of organic mulch onto bare soil within 2 to 3 feet from the base of the trunk (removing any grass first, if necessary). Do not allow the mulch to directly contact the trunk.
  • Follow the rules. When planning a watering regimen, remember to follow any current watering restrictions.

Related Resources
Water Shade Trees to Avoid Drought Stress
Colorado State Forest Service Advises Watering Tress Well During Drought
Urban Trees in Danger During Drought Conditions
With Wildfires Raging Fire-Adapted Communities Crucial to Safety
Texas Has Lost 5.6 Million Trees in Cities to Current Drought