Hi Milo -
Don't worry - that's not Russian Thistle - it is some type of navarretia!
It is a cool llttle genus (literally, small statured) that has a really diverse radiation in California.
Diversity of Navarretia by county
Density gradient of native species for Navarretia within the US (data 2011). Darkest green (16 spp. Lake County, CA; Napa County, CA; Amador County, CA) indicates the highest species concentration. ©BONAP