As we turn our focus to the local effects of the drought, I have seen many browning lawns. One of the things that I am also seeing is stressed and dying trees. In many cases the only water available to trees in the landscape comes from watering the lawn.
Usually with rain, deep watering in the winter can provide a sustaining source of water for established trees. That did not happen this year. Coming out of the typically rainy season. trees were already stressed.
A large tree is difficult to replace. The shade is cooling to the yard, sidewalk and the neighborhood, and the high branches provide a place for birds to nest and squirrels to live. In contrast, a lawn or some ornamental shrubs can be replaced more easily and have less overall neighborhood and community impact.
Trees, dependent on type, have deep taproots or more shallow feeder roots closer to the surface. It is not too late to save our trees by focusing on deep root watering and slow watering at the tree drip line.
Lawn sprays typically provide an average of two gallons of water per minute per sprinkler head. If you have 10 sprinkler heads and leave the timer on for 12 minutes that is 240 gallons of water! Instead, if you change to drip and focus on just watering larger plants and trees, that can be reduced to 2 to 4 gallons of water per hour with a small drip system. Drip should be left on to start for 3 to 6 hours, expending only 24 gallons twice a week and then decreased as the tree returns to vigor to once a week.
Lesley Miles AIA, LEED AP