Lyonothamnus floribundus ssp. floribundus, the Santa Catalina Island Ironwood, is endemic to Santa Catalina Island, one of the Channel Islands in Southern California. The trees occur in small groves, with all trunks within a grove being clones representing a single genetic individual. There are only around 110 groves of Catalina ironwood remaining.
It is rare in cultivation, while the other Island Ironwood subspecies, Lyonothamnus floribundus ssp. asplenifolius, the Santa Cruz Island Ironwood, is more readily available and cultivated horticulturally. It is endemic to three of the Channel Islands: Santa Cruz Island, Santa Rosa Island, and San Clemente Island.