Joshua trees, Yucca brevifolia, are found only in North America in the states of California, Arizona, Utah, and Nevada. Confined mostly to the Mojave Desert between 2,000 and 6,000 feet, they thrive in the open grasslands of Queen Valley and Lost Horse Valley in Joshua Tree National Park.
Joshua trees can grow from seed or from an underground rhizome of another Joshua tree. They are slow growers: new seedlings may reach a height of several inches in their first few years, then only half an inch a year thereafter. The trunk of a Joshua tree is made of thousands of small fibers and lacks annual growth rings, making it difficult to determine the tree's age. This tree is not very sturdy because of its shallow root area and top-heavy branch system. But, if it survives the rigors of the desert, it can live a couple hundred years. The tallest tree in the park is about 40 feet tall.
One of the most beautiful spectacles in spring is the creamy white blossoms of flowering Joshua trees. These flowers appear from February to late April. Joshua trees do not branch until after they bloom, and they don't bloom every year. Like most desert plants, their blooming is dependent on rainfall at the proper time. They also need a winter freeze before they will bloom.
Once they bloom, the trees are pollinated by the yucca moth, which spreads pollen while laying her eggs inside the flower. The moth larvae feed on the seeds of the tree, but enough seeds are left behind to produce more trees.
The name Joshua tree was given by a band of Mormons who crossed the Mojave Desert in the mid-19th century. The tree's unique shape reminded them of a Biblical story in which Joshua reaches his hands up to the sky.\n