To prepare your trees for summer, there is nothing more important than proper watering. Doing it well can be a challenge in the desert, but the following tips should help.
The first secret of watering desert trees is to know your how well your soil holds water. Because different soils drain differently, they require different amounts of water and different watering frequencies. You can use a soil probe, available at most good nurseries, to determine how quickly your soil dries out and needs water again. More on soil probes below.
Once you know the rate that water percolates through your soil, you can precisely set the DURATION of the irrigation cycle in order to water to the full depth of the root zone.
This is important because trees are commonly over-watered. We assume trees need more water because the SURFACE soil looks dry. But many desert soils have a high water-holding capacity. Three to six inches below the dry surface, the soil profile is cooler and can often hold water for several days or weeks.
The point is to avoid putting water on top of water. This is not only wasteful; it also sets up conditions for various disease pathogens.
Using the soil probe, you can also determine watering FREQUENCY, that is the number of days between waterings. The goal is to apply water when the root zone completely dries out. A simple test to determine watering frequency is to watch your trees for signs of afternoon wilting. If the leaves of your tree or shrub begin to curl at the edges (wilt) after 10 days, set your watering cycle for 8 or 9 days.
Stay tuned for my series on Irrigation next month. In the meantime, for a closer look at watering and using a soil probe, visit our Integrity Tree Service Fact Sheets here.