I think I know, but am not sure. I think this backyard volunteer is a Ruellia nudiflora (wild violet petunia) which is a low water native that grows in thickets and is host to several butterflies with great names like the Cuban Crescent, the Common Buckeye, the White peacock and the Malachite. If so I should relocate my "undesirable" ones (growing in a new pathway) off to the side so they can do their thing. It certainly likes it in the back so I should encourage it..
The rest of the plants seemed to be smiling this afternoon when I went to see how they liked the rains- the near-dead Copper Canyon daisy has new growth, the salvia's and lantanas are covered in the buds of new flowers and my scraggly butterfly weed is blooming. I hope everyone got to enjoy the outside, too!