Water plays many key roles in a tree's life. When water is in short supply, trees cannot function normally and will eventually die if the deficit is not corrected.
Newly planted trees possess only a small percentage of their original roots and must be closely monitored and watered carefully. Always check the moisture status of the soil around your tree before watering. A hand trowel or soil probe is a useful tool for performing this important investigation. If the soil is dry, water should be delivered at a slow rate using an oscillating sprinkler or soaker hose. Commercially available root feeding/watering probes can be used to deliver water directly into the rootball of recently planted B B or container- grown nursery stock. Newly planted trees should be inspected at least once a week to determine if watering is necessary, and more often during hot, dry weather. Caution, watering too frequently can also kill trees.
During extended periods of drought, large established trees also need to be watered. A single, large tree can transpire more than 100 gallons of water on a typical summer day. Before watering, check the soil moisture to a depth of 12 to 18 inches with a narrow spade or soil sampling probe about midway between the trunk of the tree and the edge of the branch spread (dripline). If the soil is dry, water with a sprinkler or soaker hose to a depth of 18 inches. Water an area at least as wide as the branch spread. Well established trees often have extensive root systems that extend far beyond the tips of the branches and will benefit from water applied to the soil outside the branch spread. Root feeding/watering probes are useful tools for irrigating trees as long as they are not inserted into the soil deeper than 12 inches and are moved frequently. If possible, avoid applying chemically softened water to trees. Frequent use of softened water may harm soil structure and injure trees.
This article originally appeared in the August 12, 1994 issue, p. 128.