These plants are 18-24" high, growing in full sun, in East Texas.
I would appreciate any help in identifying the plant.
Here is a link that might be useful:
It's a St. Johnswort for sure, however, that's the best I can do. Most of these are native but you will have to check with local experts on the pictured species. This plant is not the eurasian species that is used as an anti-depressant herb.
I was waiting for someone to say it's silphium, based on the foliage.
But the flowers look more like Wingstem, Actinomeris alternifolia. But the foliage doesn't match!
Here is a link that might be useful: Actinomeris alternifolia