I like the common name Scarlet Hedge Nettle better than Texas Betony. Whatever you call Stachys coccinea, it's in the Mint Family. Carol T found this lone example flowering in the riparian area above the dam, and Angie had her macro lens. Thanks, Fred, for confirming the i.d.
We also saw the other two acacias, namely: Cat Claw(Acacia greggi) and White Thorn(Acacia constricta).