Desert Trees: Form and Structure
It has been enormously gratifying to witness the growth in popularity of desert adapted trees in a wide array of landscape applications and their use as substitutes for traditional, high water demanding trees. This evolution in design has given rise to a landscape aesthetic that is more reflective of the desert region we live in and celebrates the beauty and diversity of this environment instead of trying to mask it. Desert adapted, multiple trunked specimens have been successfully used in streetscapes, commercial, residential, multi-family and municipal landscapes of all sizes. There has been discussion that the natural, multiple trunk form of desert species can lead to compromised structural integrity and some have suggested that single trunk forms of these trees are more appropriate and durable. While it’s clear that some desert trees come to the marketplace with defects (e.g. included bark, tight branch angles, bound roots), these are byproducts of poor quality management or poor stock selection during the propagation and production process in the nursery. The notion that desert trees should be pruned and shaped into single trunked forms, more closely resembling those of traditional, introduced, hardwood trees species, denies the basic genetics of desert species, and ignores fundamental (and evolutionary) differences between these two very different types of trees. Dr. Ed Gillman, in his recently revised “An Illustrated Guide to Pruning,” observes, "a number of small-maturing trees and shrubs...can be displayed nicely by creating a multi-trunked, multileader, or low-branched tree. Many develop a multitrunk form without pruning.” This is, quite literally, a description of the vast majority desert adapted and desert native trees.
Community or municipal landscape codes work at cross purposes when they encourage or require the planting of desert adapted species and then require that these trees be planted as single trunked or single leader specimens. Pruning desert adapted trees into unnatural single leader forms decreases structural integrity and potentially reduces durability and longevity. Severe weather events, obviously, can have catastrophic effects on the landscape. In the worst cases these effects are unfortunate and often unpreventable. The very nature of biology is the adaptation to adversity and the interaction with the environment. Desert adapted trees take their form and structure from the environment they evolved in and the conditions they have endured. Their durability, in this difficult region, is a testament to a hard won perfection they achieved after millennia of struggle. Our job is to acknowledge and respect this perfection and reflect it in our approach to nursery production methods, landscape designs, installation and maintenance.