I believe this is St. John's Wort (Hypericum calycinum). We used to see it quite a bit in Virginia, mostly used as ground cover. Haven't noticed it quite so much here in central Texas, although I think it's supposed to like warm climates and sandy soil, which seems like a perfect match. But I think in some areas it's considered an invasive weed — so not very welcome, I suppose. Still, it produces a very attractive bright yellow flower with five "ruffled" petals and many, many long central stamens.
The name St. John's Wort evidently has to do with St. John's Day celebrations and the ancient practice of gathering the flowers and burning them to ward off evil spirits. And warding off evil spirits sounds pretty good to me right now.
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