Not sure, but might be the expended flowers of an aster species.

Yes a Symphyotrichum sp. was my first thought.

This could be Symphytrichum divaricatum, Southern annual salt marsh aster. It's the only species with narrow leaves that is observed in Dallas on i nat. Not to be confused with Eurybia divaricata, the White wood aster. Most aster species kept their species names when they were moved from Aster into Symphyotrichum, Eurybia, etc. Symphyotrichum divaricatum was previously Aster subulatum var. ligulatum and Nesum elevated it to species status and named it S. dicaricatum.

Hmm, that's a good guess! Yes, Symphyotrichum divaricatum (Saltmarsh Aster) is very common down here, thanks!