Route 178 at Walker Pass is located in the southern Sierra Nevada Range, at an elevation of 5246 feet, on the boundary between the California Floristic and Desert provinces. It is also where the Pacific Crest National Scenic Trail crosses the highway as it winds north to Canada and south to Mexico.

With the exception of a short stretch of adjacent Sequoia National Forest, the lands on both sides of the highway are managed by the US Bureau of Land Management. The distinctively different floras of the Sierra Nevada and Mojave Desert collide at Walker Pass according motorists an awe-inspiring view of contrasting textures and color.

Joshua trees and pinyon pines are the most obvious members of this plant community. At least 25 species of birds nest in Joshua trees. They are also host to the yucca-boring beetle and larvae of the Navajo yucca borer butterfly.

Joshua trees are pollinated by silver-gray, night-flying moths that lay their eggs in the flowers. As the pollinated flower matures, the larvae hatch and feed on immature seeds. After the seeds have fallen to the ground, the larvae bore their way out and pupate in the soil. When the adult emerges the cycle is repeated.

Other perennial plants that loiter on or near Walker Pass include rabbitbrush, goldenbush, sagebrush, desert peach, buckwheats, and bunch grasses.

The yearly parade of annual wildflowers is always a unique display that varies with the amount rainfall the region receives.

The spring season (March-May) is the best time to observe annual plants typical of the desert such as gilias, monkeyflowers, poppies, goldfields, coreopsis, and woolly sunflowers. A multi-colored carpet beneath twisted Joshua trees makes for an image that is not soon forgotten by visitors to this arid world of gnarled life forms.