Known from only one occurrence with fewer than 15 trees in Wild Boar Gully; one of the rarest trees in CA. Mainland occurrence of one plant from LAX Co. (113C) needs confirmation; possibly introduced or hybrid with C. betuloides var. betuloides. Threatened by feral herbivores and hybridization. Recovery work in progress. See Proceedings of the California Academy of Sciences III 1:136 (1898) for original description, and Conservation Biology 3(1):52-58 (1989) for discussion of hybridization.