The national park is made up of two different deserts: the southern end of the Mojave Desert forms its western edge, while the Colorado Desert covers its eastern and southern portions. As such, the Joshua trees for which the park is named are more common in the higher elevations on the Mojave side, but here’s the funny thing: they’re not actually trees. The plants are members of the Yucca genus and can grow up to 70 feet tall, though they can take up to 50 years to reach their full size.