Tips on Tree Watering from Denver Water and the Community Tree Alliance
Sometimes your trees could use a drink. Prolonged dry periods and high winds can dry trees and top soil, and watering your trees will help ensure their optimum health.
Tree roots are not like carrots
Tree root systems can spread two to three times wider than the height of the tree. Most of the tree's absorbing roots are in the top 12 inches of soil. Water should be applied within the drip line (the critical root zone shown below).
Water deeply and slowly
Apply water so it moistens the soil in the critical root zone to a depth of 12 inches. Water with a deep root fork or needle, soaker hose or soft spray wand. Apply water to many locations under the drip line. If you use a deep root fork or needle, insert the device no deeper than eight inches into the soil.
How much water to apply
Fall and winter: To assure survival of the tree, apply 10 gallons of water for each inch of the tree's diameter. For example, a two-inch diameter tree will need 20 gallons per watering. Use a ruler to measure your tree's diameter and then refer to the schedule below.
Spring and summer: The amount of water needed depends on the tree’s diameter. Use a ruler to measure your tree's diameter and then refer to the schedule below.
When to water
During prolonged dry periods in the fall and winter (October – March), water one to two times per month. Water only when temperature is above 40 degrees and no snow cover exists. Refer to the schedule below.
In the spring and summer (April – September), trees in regularly watered turf areas should not need supplemental watering. But when trees do not get regular irrigation, water small trees weekly, medium trees three times per month and large trees two times per month. Refer to the schedule below.
Mulch helps retain soil moisture
Mulch helps conserve soil moisture. Apply organic mulch within the drip line, at a depth of four inches. It's best to eliminate turf prior to adding mulch. Leave a six-inch space between the mulch and trunk of trees. Mulch materials may include wood chips, bark, leaves and evergreen needles.
Moisture is needed to avoid disease
Stressed trees are more vulnerable to disease, insect infestations and branch death. Keep an eye out for anything that looks out of the ordinary.
