If you attend an in-person tree workshop, part of the presentation covers proper watering techniques. Below we have recapped some of the main points and added several other tips that we hope will address other issues that may come up.
1. First, we highly recommend buying a soil probe (pictured left) because it is hard to determine just how deep water is going. Often people believe that water is reaching deep into the root zone (typically 2-3 feet), but when they use a soil probe they are surprised that the water only reaches a foot underground. A soil probe will slide easily through wet soil but will be hard to push through dry soil. If you do not have a soil probe, you can use a very long screwdriver as well.
2. After planting your tree, you’ll need to determine how wide you want to water around the tree. Most water absorbing roots are located near the dripline--the area under the outer edge of the plant’s canopy--and not close to the trunk. If you are using a drip irrigation system, place the emitters along the dripline of the tree. The water will move down and horizontally as it soaks into the soil, reaching the root zone. If you are using a hose, make sure and water along the dripline area.
3. While watering frequency and depth depends on the season (refer to #7), often the rule with desert-adapted trees is deep but infrequent watering. Do not perform water soaks for more than 24 hours. Also, trees kept in standing water for more than a week will cause a desert-adapted tree enough stress for it to drop its leaves, a common stress response.
4. The rate at which your soil dries out between watering depends on the soil type you have. Most soils in the valley are clay and, therefore, watering more than once or twice a week to the proper soil depth of 2-3 feet can drown the young trees (again, a soil probe will greatly help here). Clay soil retains moisture and you will most likely not need to water your tree more than 1-2 times a week during the hottest summer months.
5. Water in the early morning or late evening so more water reaches the roots instead of being evaporated by the sun and wind.
6. Applying mulch, such as wood chips or compost, over your tree’s root zone will help keep moisture in the soil longer (and keep it warmer during the winter). Make sure and keep mulch 2-4 inches away from the tree’s trunk for proper aeration.
7. Often, first signs of tree damage is the wilting and loss of leaves or discoloration. Pay attention to the tree’s leaf growth and adjust the watering as needed.
8. As your trees grow and the weather changes, so will the watering requirements. Below is landscaping watering guidelines. Locate the desert-adapted trees section to find the suggested watering frequency and depth for each season.
(Monitoring with Soil Probes) http://region8water.colostate.edu/PDFs/hg520.pdf
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