Eastern Joshua Tree (Yucca brevifolia jaegeriana), or perhaps Yucca jaegeriana, are the signature species of the Mojave Desert: if you see Joshua trees, you are in the Mojave Desert -- no questions asked.

Eastern Joshua Trees occur in Arizona and parts of eastern California and southeastern Nevada, including around Las Vegas. Western Joshua Trees occur to the south and west. Link to distribution map.

Eastern Joshua Trees differ from Western Joshua Trees in a number of ways, but Eastern Joshua Trees are shorter, branch closer to the ground, and have shorter leaves. There are also differences in the flower, fruit, and pollinators.

Joshua trees are a major component of the Upper Sonoran (Mojave Desert Scrub) life zone, and they extend into the Upper Sonoran (Pinyon-Juniper Woodland) life zone.

Family: Agave (Agavaceae).

Other Names: tree yucca, Joshua tree yucca.

Plant Form: Upright, many branched tree, with branches starting close to the ground.

Height: usually to about 15 feet.

Trunk: generally 12-15 inches diameter, to 3 feet; brown, rough, and furrowed. Young trunks covered with dead leaves.

Leaves: long (usually 6-8 inches) and narrow, straight, pointed tip, toothed margins, dark green. Live leaves clustered at the ends of branches in dense rosettes; dead leaves stay attached for years and cover the trunks.

Flowers: greenish-white, waxy, bell shaped, to 3.5 inches long. Flowers clustered on stalks (to 1.5-feet long) at the branch tips. Blooms in the spring if there have been enough cold days during winter. These flowers are long and narrow compared to Western Joshua Tree flowers.

Seeds: Occur in green seedpods about 1.5 inches wide and 4 inches long. These seedpods are long and narrow compared to Western Joshua Tree seedpods. Inside a seedpod, seeds are held in several sets. Each set contains a stack of disk-like seeds. Seeds white, developing to black when ripe.

Elevation: Usually 2,000 to 4,500 ft, but at least as high as 6912 ft in the Spring Mountains.

Comments: Joshua trees are said to have gotten their common name from Mormon settlers who likened the tree to the biblical prophet Joshua with his arms uplifted towards the sky in prayer.

Joshua trees can live 300 years.

Joshua Trees are pollinated by Tegeticula moths (family Prodoxidae), commonly known as Yucca Moths. Eastern Joshua Trees are pollinated by Eastern Joshua Tree Moths (Tegeticula antithetica)

Many species of wildlife use Joshua trees. In places where Joshua trees are the only "trees" around, woodpeckers drill nest holes into the trunks, holes that are then used by other nesting birds (e.g., Ash-throated Flycatcher) in later years. Desert Night Lizards depend entirely on Joshua trees and other yuccas, living only under the bark and in the dead trunks of these species. Desert Woodrats often nest in the hollow trunks of dead Joshua trees.

During drought and other times of stress, Desert Woodrats sometimes chew off the leaves of Joshua Trees. Sometimes the cut leaves are left on the ground, other times they seem to have been chewed or eaten, and sometimes they are used to armor the Woodrat's nest.

During mega-droughts, woodrats and other species (Black-tailed Jackrabbit, Feral Horse) will chew the bark off Joshua trees to get at moist tissue. If enough bark is removed, the Joshua tree will die. Valley Pocket Gophers will chew the roots and come up inside the trunk of a Joshua Tree, which then topples over in high winds and die.