A new and distinct cultivar of Oenothera drummondii identified as TX-12-5 characterized by 1) a propensity for free flowering (numerous flowers over an extended time and range of photoperiods), 2) a low spreading growth habit (typically less than 30 cm tall) with a dense canopy of foliage, 3) a grey-green shade of foliage compared to the green of most of the species, and 4) consistently bright yellow flowers.