Joshua Tree (Yucca brevifolia) and moon
The Joshua Tree from Joshua Tree National Park.
Joshua trees are fast growers for the desert; new seedlings may grow at an average rate of 7.6 cm (3.0 in) per year in their first ten years, then only grow about 3.8 cm (1.5 in) per 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 has a top-heavy branch system, but also has what has been described as a "deep and extensive" root system, with roots possibly reaching up to 11 m (36 ft) away. If it survives the rigors of the desert it can live for hundreds of years with some specimens surviving up to a thousand years. The tallest trees reach about 15 m (49 ft). New plants can grow from seed, but in some populations, new stems grow from underground rhizomes that spread out around the Joshua tree.