The Joshua Tree, Yucca brevifolia, is the namesake of the Joshua Tree National Park. Actually, it is not really a tree, but rather a species of yucca plant. These trees are giant members of the lily family, reaching a height of nearly 50 feet. The tallest Joshua Tree in the park is 40 feet tall and is estimated to be about 900 yars old. Since they are not proper trees, they have no annual growth rings, but their average growth rate of 0.5 inches per year can be used to calculate the approximate age of a plant.

 
Joshua trees are found only in the southwestern United States, in the states of California, Arizona, Utah, and Nevada, at elevations above 3,000 feet. They seem to require temperatures below freezing in order to bloom and reproduce. The Joshua tree plays an important role in the desert, providing food and shelter for many of the desert's birds, mammals, insects and lizards.

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The Joshua Tree blooms in early spring, from February or March until late April or May, and is a truly beautiful site. Its creamy white bell-shaped blossoms are 1.25 to 1.5 inches long, and though beautiful to behold, have a rather unpleasant odor. Joshua trees do not branch until after they bloom, and not all trees flower every year. Some Joshua trees grow straight stalks. These trees have never bloomed, which is why they are branchless.

Pollination of Joshua Tree flowers is accomplished only by the female Pronuba Moth, also called the yucca moth. She transfers pollen from flower to flower as she lays her eggs inside their ovaries. As the seeds develope, the moth eggs hatch into larve and feed on the seeds. This symbiotic relationship provides for the pollination of the Joshua Tree while providing food for the moth larvae.

Joshua trees bear an elliptical green-brown fruit, about 2.5 to 4 inches long. The fruit dries out and falls to the ground soon after it reaches maturity.