Joshua and the yuccas
Joshua Tree National Park is well-known for the ~1.5 million Joshua trees that cover the park and for the fascinating rock formations.
The Joshua tree, yucca brevifolia, is a member of the yucca family. As can be seen above, the Joshua tree has shorter leaves than its smaller cousin the Mojave yucca. The Mojave yucca's leaves are long and have little white fibers growing out of them.
The oldest Joshua tree in the park is 40 feet tall and is estimated to be roughly 300 years old! Unlike pine and oak trees, the Joshua tree does not have any growth rings so it is difficult to estimate the age of the tree. The average growth rate of the Joshua tree is 0.5-1 inch per year and may vary from 0 to 7 inches depending on the rainfall.
The landscape of Joshua Tree National Park is a collection of ancient rocks that were formed many years ago. Lava flowed upward and cooled while still below the surface. A series of horizontal and vertical cracks formed in the rock. As ground-water worked its way through the cracks, rectangular stones were transformed into unlikely shapes. These rock piles were exposed after flash floods began washing away the surface soil that covered the rocks. Today you can see rock piles that look like arches, whales, tulips, skulls and more.