Plant Fact Sheet

Agavaceae
Joshua Tree
Yucca brevifolia

The Joshua tree is the largest of all U.S. yuccas, commonly reaching 30 feet, with larger plants reaching to 50 feet. One living near Lancaster, California may be 80 feet tall. These trees can be quite wide spreading, with branches extending to 30 feet. Endemic to the Mojave Desert, the Joshua tree is often used as the classic indicator plant. Joshua trees occur at elevations of 2,000 to 6,000 feet in California, Nevada, Utah, and Arizona.

Joshua trees have relatively short leaf blades and the bark is rough and grayish brown. The dull lime-green leaves circle around the stems and are concentrated near the ends of the branches. The canopy on Joshua trees tends to tilt a little to the south, reminiscent of a solar panel. Yet, Joshua trees have such a wide range of shapes, with bent and contorted branches, that it seems no two plants are alike. A forest of Joshua trees is truly a sight to behold.

The flowers appear in March from the terminal points of the stems and are arranged densely in the panicle or compound flower structure. The individual flowers are cream to greenish white in color and have tough, leathery petals. The flowers produce a mild unpleasant odor. After a branch tip flowers it usually forms buds that lead to more branches. The other way Joshua trees branch is if the growing terminus is injured.

The Joshua tree has a special relationship with its pollinator, the yucca moth. This relationship is mutually beneficial for both the moth and the Joshua tree. The yucca moth visits the flowers during the night. She obtains enough pollen to make a ball that will fit into the pistil of a selected flower then injects her eggs into the pistil. Now that she has fertilized the flower, the fleshy ovary of the seedpod that will begin to grow will provide protection for her offspring. The developing seeds will provide a food source for the larvae, but they will not eat all the seeds, leaving enough for dispersal, and the reproduction of the Joshua tree.

Joshua trees germinate easily from seed, but raising a seedling into a larger plant may prove to be difficult. Joshua trees prefer sunny locations with fast draining soil. The Living Desert has a small collection of Joshua trees located in the Mojave Desert garden.
Some plants have been living in the garden since the late 1970s, and new trees are added yearly when plants are available. At the Living Desert, new Joshua Trees are primarily obtained through the City of Yucca Valley’s Joshua Tree Adoption Program.