Although most of the cactus identification books I've looked say the Graham club cholla blooms in May, I'm pretty sure that this is a cholla. It was in bloom in April, but it was at lower elevation so maybe that explains the early bloom. The delicate bloom on this cactus is one of the prettiest I photographed on this trip.

Photo Details: Nikon N90s, Nikon 85.2.8 Tilt Shift, Velvia, f11@250, Manfrotto CF4221 w/Kirk BH-1, diffuser.