Yucca brevifolia

 Yucca brevifolia (Joshua tree) ( )

Asparagaceae

• Joshua tree is a true arboreal species that commonly attains a height of 30 ft or more, with some individuals larger with massive, branched crowns. The species occurs widely in a ring of higher elevation stands of creosote bush scrub around the Mojave Desert, although present at elevations above 6, 000  ft in the southern Inyo Range to the north of Death Valley. Two varieties of Joshua tree are recognized by botanists. The variety brevifolia is distributed in the western and northern Mojave Desert from north of Death Valley south to Joshua Tree National Park, with a western limit of distribution in the Techachapi Mountains near Tejon Pass. It is taller, branches higher on the trunk, and has longer leaves than the variety jageriana which is distributed in the northeastern Mojave Desert from the Mojave National Preserve eastward into Nevada and northern Arizona. Joshua trees are slow growing, typically adding only a few inches of height annually. Joshua tees are slow growing, typically adding only a few inches of height annually. Older dead leaves retain their stiffness and are bent downward, playing a role in preventing rodents from climbing up the stems and feeding on the fruits. From March-May dense clusters of cream-colored flowers are produced at the branch tips. The Joshua tree seeds are spongy rather than fleshy as in other yucca species-suggesting that this species forms its own distinct group within the genus. Although there is no absolute means of aging Joshua trees because, as monocots, they lack tree rings, it has been suggested that typical life spans are 150 years and that larger individuals may live to 300 years. Some suggest that the largest Joshua trees may reach an 1,000 years, which is highly speculative at best. "California Desert Plants, Philip W Rundel, Robert J Gustaffson, Michael E Kauffmann."