The Joshua tree (yucca brevifolia) is actually the largest member of the lily family. Its taxonomic classification is as a monocotyledonous tree, defined in part as having no annual rings (similar to the palm). This makes it difficult to determine the age of Joshua trees. However, they grow about a half-inch per year; the tallest Joshua tree in Joshua Tree National Park is 40 feet tall, which would make it almost 1,000 years old. Most don't live that long, because they're somewhat precarious, having top-heavy branches and shallow roots.
Monocotyledonous is also defined as a plant whose embryo has only one cotyledon, a subgroup that includes grasses and orchids.
They bloom between February and April, though not necessarily every year; it depends on sufficient rainfall at a critical moment in the annual life cycle. The flowers consist of six petals, from a creamy-white to a silvery-green color. When they bloom, the flowers are pollinated by the yucca moth, which also lays its eggs inside the flower. Joshua trees can grow from seed; they can also sprout from the rhizome (an underground shoot or root) of another tree.
Joshuas grow mostly in the Mojave Desert, but they're also found keeping company with saguaro cactus in the Sonoran Desert in western Arizona and even growing among pine trees in the San Bernardino Mountains in southern California. They're favored elevation is between 2,000 and 5,000 feet.
Native Americans used the tough leaves of the tree to weave baskets and sandals; they also ate the flower buds raw or roasted.
The Joshua tree was named by Mormon missionaries traveling from Salt Lake City to southern California in the mid-19th century. The limb-like branches of the plant reminded them of the Biblical story in which Joshua reaches his hands to the sky.
The best place to see Joshua trees is at Joshua Tree National Park, a million-acre preserve east of Palm Springs in southeastern California.
