When my family moved to Hesperia in June 1964, it didn't take long before my fascination with the Joshua trees grew. In fact, it became sort of an obsession and sparked my general interest in the Mojave Desert. This culminated with my private publication of a book, "Joshua is a Tree," in 1980. I have discovered much since that time and I've decided to share those thoughts with readers of the Star. First, here are the basics.


The Joshua tree, yucca brevifolia, is related to other notable desert yuccas, such as the Mojave (or Great) yucca, yucca schidigera, and the Adam's needle (yucca filamentosa), and others. Yuccas are included in the botanical family that includes the lily. That is why the Joshua tree is sometimes nicknamed a "tree lily." But although yuccas in general, share certain traits; such as the long, narrow leaves and basic root structure; the desert yucca varieties, especially the Joshua tree, have unique characteristics of their own.


One is indeed, the root system. Each root of a Joshua tree (and other desert yuccas) is an individual entity. They start at the root ball and spread out from the tree in all directions, remaining close enough to the soil surface to immediately make use of rainfall and far enough down to escape the heat and sunlight. If a root is cut anywhere along its length, it dies off and must regenerate from the root ball itself. The only part that grows is the root tip. The root is surrounded by a shell that allows for a one-way passage of moisture. The root system of a fairly large and old Joshua tree may encompass an entire acre. The buried base of the tree may actually be several times the visible diameter of the trunk. This massive base, not the roots themselves, is what provides basic stability to the Joshua tree.


The Joshua tree is a true xerophyte, a plant that is uniquely adapted to the desert. It is a true desert dweller, able to withstand conditions that would kill the average plant. Its long, narrow leaves (which I call spines) are capable of producing photosynthesis, without which a plant cannot live and grow, but without losing moisture. This is a common trait among xerophytes. All desert yuccas share this trait and so do the drought-tolerant California junipers, greasewood (creosote), and various cacti. The spines of the Joshua tree have another unique characteristic among desert xerophytes: they cause the tree to have a "solar orientation." That is to say, the tree is born facing a particular direction, and must remain at that same critical orientation or it will perish. A lot of Joshua trees, are considerately transplanted without knowledge of this fact, and most of them don't survive.


The Joshua tree, however, goes much further, storing a "moisture reserve" from good times to tide it over dry spells. The entire tree's metabolism is dependent on this reserve. We will explore this remarkable trait in part two, next month. For now, strive to leave them alone. They belong here and we don't!