Range
Joshua
Trees, Yucca brevifolia, grow in the Mojave Desert of southwest California, Nevada,
Utah and Arizona, at elevations from 2,000 to 6,000 feet.
Habitat
The Joshua Tree likes dry soils on plains, slopes and mesas, often growing in groves.
Flowers
The
Joshua Tree has bell-shaped blooms, 1.25 to 1.5 inches large, each with 6 creamy,
yellow-green sepals, crowded into 12 to 18 inch, many-branched clusters
with an unpleasant odor. The trees bloom mostly in the spring, although not all
of them will flower annually.
Fruit
The
fruit is elliptical and
green-brown. Six-celled, 2.5 to 4 inches, and somewhat fleshy, it dries and falls
soon after maturity in late spring revealing many flat seeds.
Description
The Joshua Tree, the largest of the yuccas, grows only in the Mojave Desert. Natural stands of this picturesque, spike-leafed evergreen grow nowhere else in the world. Its height varies from 15-40 feet with a diameter of 1-3 feet.
Originally
thought to be members of the Agave (Century Plant) Family, the Joshua Tree and
other yuccas have been reclassified as members of the Lily (Liliaceae)
Family. Two variations of the Joshua Tree are classified as J. brevifolia var. herbertii and J.
var. jaegeriana.
Joshua
Trees (and most other yuccas) rely on the female Pronuba Moth
(Tegeticula) for
pollination. No other animal visiting the blooms transfers the pollen from one
flower to another. In fact, the female Yucca Moth has evolved special organs
to collect and distribute the pollen onto the surface of the flower. She
lays her eggs in the flowers' ovaries, and when the larvae hatch, they feed on
the yucca seeds.
Without the moth's pollination, the Joshua Tree could not reproduce, nor could the moth, whose larvae would have no seeds to eat. Although an old Joshua Trees can sprout new plants from its roots, only the seeds produced in pollinated flowers can scatter far enough to establish a new stand.
Mormon
pioneers are said to have named this species "Joshua" Tree because
it mimicked the Old Testament prophet Joshua waving them, with upraised arms,
on toward the promised land. This unique species grows abundantly at Joshua Tree
Click
here to read more about the Yucca Moth.
Want to grow your own Joshua Tree?
Desert Plant & Wildflower Index
Joshua Tree National Park
Mojave Yucca
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