Plants spreading or decumbent, 1-2 × 1-6 dm. Leaf blades 1.5-5 × 0.3-0.7(-1) cm. Involucres 2.5-4 mm, margins white. Flowering May-Sep. Sandy to gravelly places, coastal scrub communities, oak woodlands; of conservation concern; 10-300 m; Calif. Variety robusta is known only from the immediate coast in southern Santa Cruz County and extreme northern Monterey County. Nineteenth-century collections were made in Alameda County, the last in 1891, and in Santa Clara County, the last in 1888. The last collection from San Mateo County was made in 1913. Inland populations were known from Santa Cruz County in the 1930s, but none has been seen there since. Nearly all extant populations are known only from coastal state parks.
The type of var. robusta is a more upright, inland expression compared to the decumbent plants found along the coast. It is possible that the coastal form deserves recognition but until an extant population of the inland expression is found, no name is proposed. Robust spineflower is federally listed as endangered.
This project made possible by National Science Foundation Award 1410069