This member of the Primrose family (Onagraceae) is now known as Scarlet Beeblossom (Oenothera suffrutescens) but used to be called Scarlet Gaura (Gaura coccinea). Also, White Gaura (Gaura lindheimeri) is now called Oenothera lindheimeri and has a new common name: Lindheimer’s Beeblossom. I relate all this because anyone using old field guides will struggle with identifying these plants because of the reclassification.
The plant pictured is most likely O. suffrutescens. However, be warned that white and scarlet gaura look basically the same, their flowers go through the same stages and their ranges overlap in Texas. White gaura is found in Texas and Lousiana while scarlet gaura goes all over the central US and into Canada. The reddish brown anthers on the tips of the 8 stamens indicates that the pictured plant is the scarlet gaura or Scarlet Beeblossom. If you had yellow anthers, you might have Lindheimer’ beeblossom. I invite you to visit NPIN and USDA websites to see their photos.
The flowers of these plants are short lived and their petals begin as white on the first day, pink on the second, and wither to scarlet on the third. So whatever color bloom you see, check the anthers; if they are reddish brown, you might have Scarlet Beeblossom.
These plants are found in grasslands or open woodlands and are often disguised by tall grasses or other wildflowers. They are perennial so you can return and see them at the same location each year if you’re so inclined.