Watering Needed for Older Trees During Missouri Drought

Story by: Guest Contributor

First posted on 08-22-2007

As drought conditions continue, even well-established trees and shrubs will come under severe stress during August and September, making it advisable to do some watering to ensure survival of particularly valuable trees, said a University of Missouri Extension horticulturist.

“In general, the larger a tree, the more drought tolerant it will be because well-established trees have massive root systems,” said Chris Starbuck.

“But once the subsoil has been depleted, trees lose this advantage and must compete with other plants for moisture near the surface,” he said.

It takes a tremendous volume of water to replenish the soil moisture throughout the entire root zone of a large tree.

Lawn irrigation typically has little impact on large trees. Most homeowners irrigate frequently for a short period of time. This maintains enough moisture in the upper 3 inches of soil to keep the turfgrass green.

Using a sprinkler system attached to a garden hose delivering 5 gallons per minute would take days of continuous irrigation to water just one such tree, he said.

“Fortunately, wetting even a small portion of a tree’s root zone will greatly reduce drought stress,” he said

An effective method to reduce drought stress for a large tree is to use a soaker hose. A 50-foot length of this type of hose can be attached with the appropriate hose fittings at both ends to a Y-adapter on the end of a garden hose. This provides a double soaker with reasonably uniform delivery.

Running water for an hour will wet a band about 2 feet wide with about 200 gallons of water. This should be equivalent to about a 6-inch rain over 5 percent of a large tree’s root zone.

Repeating this procedure three or four times in different locations during drought conditions should significantly reduce drought stress without using an inordinate amount of water, he said.

Another approach is to divert water from downspouts so that during a rain event, some of the diverted water soaks into tree root zones rather than running into a storm sewer.

Make sure not to drown your trees during any periods of excessive rainfall, he said. For more information on trees, go to: http://extension.missouri.edu/explore/

Share | |