Ferocactus viridescens is a rare species of barrel cactus known by several common names  including Coast barrel cactus and San Diego barrel cactus. It is native to southern California and northern Baja California. Most of its native range is in San Diego County  California  where it is threatened by development  agriculture  and other alterations in its habitat.San Diego Barrel Cactus is spherical to cylindric with red spines that turn to gray as they age. A circle of large yellow flowers adorn the top of the barrel in late spring. Although it naturally grows on the coast this rare cactus will thrive inland where there is not risk of frost.It is included in the CNPS Inventory of Rare and Endangered Plants Rank 2B.1