This is not a bottlebrush plant. I just want to get that out of the way up front.
The flower of a bottlebrush plant looks like, well, a bottle brush. See for yourself here. So when I looked up bottlebrush plant, I realized that the name I’d been keeping in my head for this plant was wrong.
Some flailing around on the internet led nowhere (although you’d think that “red bushy flower” should have been enough), but a stop at the Environmental Education Center in Chandler (in whose grounds I had photographed the mystery flower) straightened everything out after the requisite period of hand-waving.
It is, of course, a Baja fairy duster. Because it looks like, well, a duster. I mean, no one would call this a bottlebrush plant.