This note addresses the identification and California distribution of Psorothamnus fremontii (A. Gray) Barneby s.l. and P. arborescens (A. Gray) Barneby s.l. Both plants are generically known as indigo bush. Psorothamnus fremontii, sometimes called Fremont's indigo bush, can only be distinguished from P. arborescens by analysis of the seed pods, which differ in size, arrangement and exudates of their glands. The distribution of P. fremontii is very limited in California, restricted to the Grapevine Mountains, in Death Valley National Park, near the Nevada border, and the Providence Mountains, California State Recreation Area and nearby Lavic. Psorothamnus arborescens is much more common in California and occurs throughout the Mojave Desert and barely into the Great Basin Desert, from near Mount San Jacinto to the White Mountains.