High Quality Content by WIKIPEDIA articles! Camissonia benitensis is a species of evening primrose known by the common name San Benito evening primrose (oddly, it blooms only in the early morning). It is endemic to California, where its range includes far southern San Benito County, far western Fresno County, and far eastern Monterey County. The species is a strict serpentine endemic, meaning that it is always found growing on serpentine soils. Serpentine is an ultramafic rock. It weathers to produce soils with characteristically low levels of nutrients like nitrogen, phosphorus, potassium, and calcium, and high levels of magnesium and heavy metals including nickel and chromium. A major, consistent chemical feature of serpentine soil is a bioavailable calcium:magnesium ratio much less than 1. Most nonserpentine soils have a ratio far greater than 1 (more calcium and much less magnesium). The extreme chemical characteristics of serpentine soils give rise to uniquely-adapted and rare serpentine endemic plant species such as San Benito evening primrose.