Since the weather has cooled, unexpected wildflowers from last year's fall sowing have started to emerge, and a couple of new varieties that have popped up that weren't in the spring beds. I have no idea what any of them are. They could be weeds for all I know.
Several tiny plants with orange flowers have already bloomed. The five-petaled flowers are only 1/4 inch in diameter, with a magenta center. The leaves are also quite small. This macro photo is deceptive as to the size of these flowers and leaves. I’ve looked through Kirti Mathura's book “The Arizona Low Desert Flower Garden,” and can't find anything that even remotely resembles this flowering plant.
I'll soon be clearing out this planting area in preparation for sowing new seeds, so whether wildflower or weed, these little cuties will have to go.
"What is a weed?A weed is a plant whose virtues have not yet been discovered."
NOTE: Identified by Sara at Farming Friends as Scarlet Pimpernel (Anagallis arvensis). It's definitely a weed, and poisonous, but it has been used as a folk remedy for various ailments.