Senna covesii (desert senna) ( )

Cassia covessi

Cove's senna is a smaller plant than Senna armata, but has large, more persistent gray leaves covered by dense white hairs. It also displays stem photosynthesis. Cove's senna is largely restricted to washes in the Sonoran Desert and has a CNPS Rare Plant Rank 2B: plants rare, threatened, or endangered in California and elsewhere. "California Desert Plants, Philip W Rundel, Robert J Gustafson, Michael E Kauffmann."
The desert senna is an herb with rusty-yellow flowers rising from woody perennial woodstocks. It inhabits dry, rocky slopes and mesas, adding golden hues to early summer and late fall when few other shrubs bloom. Nearly every year, it can be found flowering somewhere between mid-April and mid-November; sometimes a few flowers open in March or even earlier. The nectarless flowers are "buzz-pollinated" by bees which use their flight muscles to vibrate the pollen free from the anthers. "Arizona Highways Presents Desert Wildflowers, 1988".