If you are new to the Tucson and Green Valley area, you may find desert plant care a bit mystifying. To take the mystery out of watering, feeding and pruning, basically it comes down to some simple rules of thumb. This article will focus on fertilizing.
It may sound contrary to what you think about trees and shrubs, but regular feeding of desert landscape plants (and actually, all other landscape plants) is not necessary. In fact, it can bad for them.
Native desert trees in the legume family, including mesquite, palo verde, acacia and ironwood, all have the ability to produce their own nitrogen from the air. This process, called nitrogen fixation, produces food for these plants without any help from us. Additionally, it is important to note that if you do feed nitrogen to them, they ‘forget’ how to do it themselves. Why waste time and money and risk polluting our ground water? Don’t feed native trees.
As for other landscape trees and shrubs, fertilizer is not necessary for healthy plants. The more you feed trees, the more they grow. Why is this bad? Because trees have an ‘energy budget’ that is carefully proportioned for plant health. Throw that budget off kilter, such as with fertilizing, the tree will sacrifice something else. If a tree is encouraged to grow faster and produce more leaves, you will get a tall leggy plant at the nursery, or in a landscape situation, you get a tree that attracts insect pests and disease. This is because they cut back on defense chemicals to grow more, and reduce carbohydrate storage for backup during lean times.
Unless you are trying to grow fruit trees or exotic plants that can’t handle our desert soils, don’t feed them!
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