Known from fewer than twenty occurrences. Threatened by road maintenance. See Bulletin of the Torrey Botanical Club 36:605 (1909) for original description, and American Midland Naturalist 58(2):509 (1957) for revised nomenclature.
California Native Plant Society (CNPS).
Inventory of Rare and Endangered Plants (online edition, v8-01a).
California Native Plant Society. Sacramento, CA. Accessed on
.