Updated October 17 at 1:35pm Pacific time: Tom Chester has identified this plant as Stephanomeria diegensis. The entry written below was written for when the plant was identified as Stephanomeria virgata – see comments below.

Thank you to dionysia@Flickr for today's photograph. dionysia is a first-time contributor to BPotD (original | BPotD Flickr Group Pool). Many thanks!

Rod wire-lettuce or twiggy-wreath plant is native to Oregon, Nevada and California (and considering its presence in San Diego, presumably parts of Mexico). It is an annual of disturbed places, so like yesterday's Tithonia, is often considered a weed.

The Jepson Manual recognizes two subspecies of Stephanomeria virgata, the few-flowered Stephanomeria virgata subsp. pleurocarpa and Stephanomeria virgata subsp. virgata. However, sometimes someone takes a closer look at oft-overlooked plants, and shares observations that seem to disagree with what's been published, such as Tom Chester's examination of Stephanomeria virgata and Stephanomeria diegensis (Jepson's account of Stephanomeria diegensis). The Flora of North America treatment of Stephanomeria also needs to be thrown into the mix (though it largely relies on older treatments, so again differs from Chester's observations). However, it does go some way to explaining the problems: four hair-pulling words to any taxonomist, “Hybrids are found frequently”.