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- 12. Trees are Thirsty and Need a Drink - Top
- Trees are once again beginning to suffer from a lack of rainfall. We've had nearly three months of dry weather combined with above normal temperatures. It will be yet another month before we can hope for relief from monsoon rains. So now is the time to give thirsty trees a good long drink.
Large trees should be given the first priority in watering. Pines, eucylptus, elm, ash, poplar, sycamore and oak are some of our largest growing species. Next in line for watering come the true desert types, such as palo verde, mesquite, desert willow, acacia, and ironwood. Just because they grow naturally in the desert doesn't mean they don't need water. Coming out of a normal winter they would have received nearly 6 inches of rain. Instead, over the past 6 months they have received, on average, less than 2 inches!
A soaker hose is most effective in watering large trees. Coil the hose around the tree, beginning two or three feet from the trunk. Continue spiraling the hose out at least a few feet beyond the ends of the branches. Maintain a two foot spacing between the circling hose as you go. If you can't cover the entire area at one time, then water the tree roots in sections. When your done with one section, then begin watering another. Water should be applied until the top two feet of soil is moistened. This will take some time.
Periodically check when applying water to see how deep the moisture has penetrated. To do this, use a metal rod, such as a three foot long re-bar which can be purchased at hardware or building supply stores. When the soil is moistened, the rod can be pushed in to the depth of wetting. Try pushing the rod down in several locations. Because of rocks and other soil debris, the probe may strike one of these objects and give you a false reading. Try another spot. You should wet the soil down to a depth of 3 feet; the potential rooting depth for trees. Deep watering will provide a reservoir of soil moisture that will sustain the tree for a longer period of time.
Another way to water is to use the basin method. Build a small soil berm that forms a circle around the tree a few feet beyond the branch ends. This berm will serve as a dam to hold the water in until it can be absorbed by the soil. Rapidly fill the basin with water and allow it to soak into the soil. Repeat this process until the soil has been moistened down three feet deep.
These recommendations are for trees that are not being regularly irrigated. It also applies to medium and large trees that are not being watered sufficiently by drip irrigation. Less than 10 emitters on such trees means you better hand water using the previously stated recommendations. Long-term, you should add more drip emitters! At least have enough to uniformly wet the area under the canopy of the tree. Space emitters about three feet apart on heavy, slow-draining soils. On sandy, well-drained soils the spacing should be closer, probably about one foot.
One thorough watering now should sustain the tree until monsoon rains arrive in late June or early July. Also check the condition of other landscape plants and water as needed.
Trees are one of the most important components of our urban environment, especially here in the desert. They provide cooling shade, oxygen to breath, filtration of air pollutants and pollens, wind buffering, soil improvement and beauty. They're also your most important and valuable home landscape asset. Keep that in mind when making a decision about what to water. Vegetables, flowers, ground covers and shrubs grow quickly and can be replaced at minimal cost. Not so with trees, so provide them with special care and attention!
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Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161.
Material originally appeared in Arizona Daily Star gardening column, on May 28, 2000
- Updated: May 28, 2000
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