In spring, my blog becomes a forum for my “wildflowering.” On a hillside in northern California grow two rare Mariposa lilies, listed by the Native Plant Society as endangered. Why are they so rare? Why do they occur only in limited locales?
This one is Calochortus umbellatus or Oakland star-tulip. The species is found almost exclusively in the San Francisco Bay Area, although there are a few isolated populations to the north. The flowers are tiny usually less than 2 cm. (about an inch) across.
I’ve been trying to get a good photo for years, but enlarging to that size requires perfect focus, no wind and steady hands (or a “ground” tripod). That assumes I’ve driven to Ring Mountain at the peak time. Happily this year I found dozens of them.
Ring Mountain lies north of San Francisco, on the Tiburon Peninsula of Marin County and is really more of a large hill than a mountain.
What makes it rather unique is its serpentine soil, derived from ultramafic metamorphosed rocks that have been brought to the surface by mantle driven tectonic activity. Serpentine soils are chemically harsh and toxic to most plants, so that the plants that evolved there have developed a tolerance – or even a preference – for the minerology (high in metals like magnesium, but low in calcium and nitrogen).
Several species occur ONLY on Ring Mountain and no where else on earth for this reason. Calochortus tiburonensis is an example. This can be a difficult flower to spot and not only for its small size (little more than a centimeter across). You can be looking at it, and not see it. (If you visit the mountain be careful not to step or sit on them!) The gold-greenish-brown colors are camouflaged against grasses and rocks.
Aren’t they unique looking? I love their funny “beards.” A fire or some other disaster and the whole species could be gone forever. So I visit them every year and admire their view of the Bay.