Water is the single most limiting essential resource for tree survival and growth.
Drought conditions can severely affect young and old trees alike leading to tree decline, pest problems, and non-recoverable damage as well as decreased rates of diameter and height growth. More than eighty percent of the variation in tree growth is because of water supply.1 Although providing adequate water to newly planted trees is essential, replacing older, more valuable trees lost or damaged due to lack of water can be especially difficult since they can take decades to grow to the same size. With the many social, economic and environmental benefits that trees provide it is important to continue caring for our trees even in times of drought and tightening water restrictions.
Newly planted trees should be regularly watered for the first three years. Water newly planted trees every few days initially, then once a week depending on soil conditions and rainfall. Weekly to monthly watering should continue until the tree is established in the landscape.
Established, mature trees should be watered every 2 to 4 weeks during drought conditions by thoroughly wetting the top 12 inches of soil under the tree's canopy. This may takes several hours or more depending on what type of application devices are available to you. If you have limited time to devote to your trees, it is better to completely wet a small area than to only wet the surface few inches over a large area. Limit pedestrian, mower and vehicle traffic under the tree.2
A good slow soaking over several hours is the most efficient way to water trees. Using a soaker hose, drip irrigation, a Tree gator watering bag, or slow drip bucket which applies water at ground level is the best way to accomplish this and to avoid water loss due to evaporation or runoff. This method also focuses the water over the root area and keeps the leaves and trunk dry which can prevent opportunities for harmful pests and diseases. Don't over water. Too much water can kill a tree by eliminating the air from the soil and suffocating the roots. The soil should not stay saturated, but have time to dry out between waterings.
As a general rule, 2 gallons of water should be applied for every 1" of tree diameter.
- 1 Coder, Kim D. 1999
- 2 Gilman, Edward F. 2007