August 19, 2020 Castilleja exserta ssp. exserta Purple Owl’s Clover Lush spring display at the Skyline Serpentine Prairie: goldfields (Lasthenia californica), purple owl’s clover (Castilleja exserta), and new leaves of soaproot (Chlorogalum pomeridianum). Photo by Lech Naumovich.Purple owl's clover (Castilleja exserta ssp. exserta). Photo by Elsa de Becker. Where to see itWhere to Find Beautiful Native Plants Now: Mount Diablo State Park’s Serpentine SoilSkyline Serpentine Prairie Revisited