Forgot to post my picture

That looks like Argemony mexicana to me also. While the white species is common throughout the plains states and across the desert southwest, the

MEXICANA species is limited in Texas to the southern third of the state according to USDA's Natural Resources Conservation Service. Zoom in to see more detail on the map. There is disagreement as to whether this species is truly native to the southeastern U.S. or if it was introduced and has naturalized. It can be a serious weed where it was INTRODUCED in other parts of the world.