Coast Rock Cress (Arabis blepharopbylla)

The rugged, rocky slopes and ridges of the northern Santa Cruz Mountains provide stunning views and spectacular botanizing at any time of year. The northern or Franciscan coastal scrub habitat, interspersed with patches of coastal terrace prairie, supports a diversity of herbaceous and shrub species perhaps unparalleled anywhere else in California. While the hiking may be challenging at times, it is easily forgotten in the anticipation of another breathtaking view and yet another suite of native wildflowers around every bend.

Early spring is a very rewarding time to hunt for wildflowers along the trails of San Bruno Mountain, Montara Mountain, and Twin Peaks. If you look around on rocky outcrops between February and April, you’re likely to spot one of our prettiest wildflowers, coast rock cress. This herbaceous perennial member of the mustard family (Brassicaceae) is notable for its bright, fragrant, rose-purple flowers with petals up to 3/4″ long. Blossoms develop on terminal racemes which arise on stems up to 1 2 inches tall from a simple or short-branched caudex. Rosettes of obovate, petiolate, basal leaves with entire or toothed margins reach lengths of one to three inches. Stem leaves are much reduced, sessile and widely spaced.

Coast rock cress is known from Sonoma, Marin, San Francisco, San Mateo, Santa Cruz, and Monterey Counties, as well as from a single Contra Costa County location on Red Rock Island off Point Richmond. It typically occurs in small colonies on rocky slopes dominated by grasses with sparse shrub cover. It is frequently found growing in association with seaside daisy (Erigeron glaucus), bluff lettuce (Dudleya farinosa), checker mallow (Sidalcea malvaeflora), footsteps-of-spring (Sanicula arctopoides), Indian paint brush (Castilleja aiffnis), silver bush lupine (Lupinus albifrons var. collinus), checker lily (Fritillaria affinis), and many other wildflower species.

Coast rock cress is endemic to the San Francisco Bay Area. Due to its limited geographic range and relatively infrequent occurrence, it has been placed on CNPS List 4, a watch list. Although it is not presently considered rare from a statewide perspective and its vulnerability and susceptibility to threat appear low at this time, CNPS regards the species uncommon enough that its status should be monitored regularly. Coast rock cress has no formal status as a federal or state-protected species. However, due to its CNPS listing, the California Department of Fish and Game treats as a “Special Plant Species” and recommends that impacts to it be addressed in environmental review documents.

Late winter and early spring can be especially rewarding seasons to hike the coastal hills of San Francisco and San Mateo counties. Brisk, clear air, constantly changing array of cloud formations, and even a sprinkle or two make for an invigorating escape from office, computer terminals, phones, heated air, and responsibilities. As you move from viewpoint to viewpoint, hearing your heartbeat in your ears, you just might come across a patch of coast rock cress. This would be as good a place as any to catch your breath. Have a nice winter.