Saturday morning we attended a free seminar, courtesy of SRP (Salt River Project), our local electrical utility. SRP sponsors many programs, such as $3 per bulb discounts at major retailers for CFL and LED lightbulbs, and the free native tree give-away to Apache Junction residents at the seminar.
Every family was permitted to take up to three trees after attending a one-hour lecture on proper planting and care.
I figured, “How much do I need to know to plant a tree? ” You dig a hole, you plant the tree, and then either it dies or it grows. At least that has been my experience.
It turns out that everything I thought I knew about planting trees and shrubs was wrong. Back east, we just dropped the thing into a hole, and watered it once in a while, and it grew. I never had a tree or a bush die on me, and trust me, I was the model for neglect!
In the desert, the rules are strict if you want to succeed. For instance, I was always taught that you dug the hole two or three times as deep as the root ball, and filled the bottom with good soil mixed with compost. Here, you dig the hole only 90% as deep as the root ball – the ball of the tree must be above ground. Only the larger tap roots should be under the dirt.
The important thing is to dig the hole 3 to 5 times as wide as the root ball. in the desert, the roots spread out, not down. Also, only fill the hole with the same local dirt you dug. Adding fertilizer or compost will speed growth of the roots, but will eventually cause them to die off.
For mulch – crushed granite is best in the desert environment. Tree bark mulch will blow or wash away. The mulch serves to keep the soil around the roots moist.
And I was always told not to water the root ball, water around it to force the roots to spread. This is true once the tree is established, but when newly planted it is critical to keep the root ball moist (not wet)
Which brings us back to the hole we dug to plant the tree. The Sonoran desert is not like the Sahara – with white sand. The ground is covered with a half inch of sand and stone; the dirt is hard-packed sedimentary rock, or rather a cement, called Caliche.
Water does not penetrate or absorb into the ground, hence our legendary floods following an inch of rain during Monsoon. While the plants do require water to grow, they do not do well under water! Any water that is not used by the tree will only cause the roots to rot if it cannot percolate into the soil.
So holes have to be punched into the pit, but not under the root ball (I used a twenty pound rod) so that extra water can drain.
For our trees, we chose two Mesquites. They offered Palo Verdes, but we already have two. They had two varieties of desert willow, we have one already, and the back alley is lined with five more.
In the back yard I planted the Native Mesquite, a twisted and hardy local tree. It is slower growing, but does not get too large. When mature it will block the morning sun from the living room. It also will add a shady spot for a future garden area with a water feature.
in the front yard (pictured) I planted the thornless Mesquite, a Chilean/native hybrid. Again, a hardy tree, it grows more quickly, and taller. It will shade the bedroom from the afternoon sun, which is important. Our bedroom tends to be the warmest room in the house, and as it faces the street, the most susceptible to outside noise.
All of the trees offered are native trees, and immune to local pests and diseases. They require very little water. They will lower the temperatures in our yard and house by several degrees, which will make a big difference in the summer with our 120° days.
We have been here three years now, and every year we have managed to decrease our electricity usage by a good bit. We have a ways to go, and there are more improvements we can make, but every little bit helps. Perhaps one day we will get solar panels.