Blackbrush: Coleogyne ramosissima, Rosaceae (rose family)
This one had me befuddled for the longest time. I thought it was a ratany, based on its small size and thorny branching structure. But the flowers were yellow, not pink like ratany's. These short, scrubby bushes surround my house, and so in a sloppy general visual sweep of the area, I gave the name "mystery thorny bush" to any of what appeared to be similar in shape and size and leaf. I had actually given up on identifying this one until I noticed one of these bushes covered in magenta flowers. I was thoroughly confused, as I had watched this plant move through its flowering phase—and they were yellow. When I got a closer look, I realized the newly blossomed shrub was indeed a ratany, not "mystery thorny bush." So I still had some work to do to resolve the mystery plant that had already exhibited its sunny blooms.
I decided to try keying it out by family, and then remembered I had a document listing all the plants in the nearby Pioneertown Mountains Preserve. Flipping to the page listing all the Rosaceae members; I began plugging them into the Calphotos website. Sure enough, it was in the rose family, and was actually a plant I had browsed by so many times but dismissed due to its descriptive name, blackbrush. The branches of this tree seemed rather light in color when viewed at close range like I had been doing. However, from a distance, these stubby little trees do appear dark, but I didn't notice because they were always mingled in with so many other shrubs and the low-contrast background of green foliage doesn't allow the plant stems to pop, as they would in winter when leaves have dropped and the sand is more visible.
Blackbrush tends to grow in stands, and the seeds don't readily germinate—they require oodles of winter rains. When a plant does establish itself, however, it sticks around for a century or longer. The yellow flowers I had spotted earlier in the season are actually the sepals, not petals. The sepals are greenish on the outside and open to reveal yellow walls that protect the pollinating organs. As the sepals shrivel up, they turn an orange-brick red, which had further confused me. Oh, nature.