The endangered Presidio Clarkia occurs in serpentine soils created from California’s state rock Serpentinite. Serpentenite occurs in fault zones and tends to have high levels of heavy metals such as zinc and magnesium and low levels of nutrients. Most of the Presidio’s grasslands have been developed or overrun by invasive European grasses. There is an additional population in the Oakland Hills.
The endangered White-rayed pentachaeta is a small annual plant with yellow disk flowers surrounded by white to purple ray flowers. This member of the sunflower family (Asteraceae) is currently known from a serpentine bunchgrass community and native prairie in two small areas of San Mateo County, both on San Francisco Water District lands. It was formerly known from Marin to Santa Cruz counties.
The threatened Marin dwarf-flax is a delicate annual plant in the flax family, with congested clusters of small rose to whitish flowers. It is found on serpentine ridges covered with bunchgrass from Marin County to San Mateo County and in a serpentine chaparral association in Marin County. There are now 20 known existing occurrences, ranging from land owned by the Marin Municipal Water District to the Presidio of San Francisco to Edgewood Park in San Mateo County to land owned by the San Francisco Water District. Residential development and road and freeway construction have eliminated five of the historically known populations. of Marin western flax.
Last updated: February 28, 2015