The first thing we need to understand is how much water a tree needs. In our low desert environment, a desert tree, such as a Mesquite or Palo Verde, will probably need no additional water other than the natural rainfall.
When initially planting desert trees, it is usually helpful to supplement natural rainfall with irrigation just for the first Summer, as this will help them recover from the shock of being planted outside of the container.
Beware of planting desert trees in a lush, maintained lawn, as extremely rapid, and chaotic growth can be the result. I once had a wonderful client who had to have her mesquite trees trimmed three times per year since they were planted in her lawn area, which gets frequent shallow watering.
Understand the Watering Needs:
For everything that is NOT a desert tree, there is a simple formula for watering established trees: water a tree two times per month in the Summer and once per month in the Winter. If you keep an eye on the tree and notice wilted leaves, then it is way past time to water. Once or twice per month may not seem often enough. It is, as long as each of the trees gets a lot of water each time.
A good, easy way to water a tree is to turn the hose on its lowest setting on the uphill side and walk away for 4-6 hours. This is important, as it will help flush salts and other chemicals that can make for poor soil in excess, below the level where roots can absorb them. Roots are not going to grow where there is little water, and there’s just nothing in it for them.
The worst thing for a tree is shallow, daily watering like that which occurs in many lawns. The trees that grew in a lawn with constant easy access to shallow water are most likely to blow over in a storm because their roots aren’t deep enough to withstand heavy winds.
It may help to picture a tree’s roots as underground ropes that anchor the heavy trunk and the wind-exposed canopy. Mulching can also help in retaining water and keep your soil moist. Therefore, you should call tree professionals who can provide onsite mulching & chipping services.
Quality of Soil:
The next thing to consider is soil quality. There is a myth that soil quality has something to do with the structural makeup of the soil. In some cases, this may be true, as is the case with sandy soils that will not hold water. For the most part, all soil problems can be alleviated through the addition of a magic ingredient. This ingredient is organic matter.
When a person takes a handful of rich, black soil and says something farmer like “this is the soil of the gods” or something dumb like that, what they really should be saying is “this dirt has lots of decayed organic matter in which plants will grow very well.”
Good soil doesn’t usually just happen on accident; it is created through the constant addition of water, which causes microbial growth, and the addition of organic material that is a natural by-product of decaying plant matter.
So, if you have “bad” soil, you can almost always fix it simply by adding mulch and water. An alternative (or supplement) to adding mulch is to plant nitrogen-fixing plants such as legumes, buckwheat or clover. These are magical bean types of plants that can absorb nitrogen from the air.
When they die, they release that nitrogen into the soil. One cheap source of organic material is the wood chips from tree services like ours. Be prepared though, if a tree service brings you a load of wood chips, it may be a lot more than you anticipated or can easily handle. You may need to spend a Saturday hauling them into your backyard.
It is not necessary or even advisable to work the wood chips into the soil. An above-ground application 4-6 inches deep is a good way to do it. A surface layer of wood chips will also have the added benefit of retaining water. I estimate that mulched trees use less than half the water of trees whose soil is exposed directly to the air.
It always amazes me when I dig down under the mulch and find water and worms and decaying matter, even if the trees haven’t been watered in a month, in such contrast with the Arizona heat blazing away above. You will be surprised at how quickly your mulch disappears.
I have an unproven theory that worm castings covering the chips are what causes the wood chips to rapidly disappear; to be integrated into the soil below. Whatever the reason, you will probably need to reapply the wood chips annually to get the best results.