Oenothera hartwegii subsp. filifolia
Syst. Bot. Monogr. 83: 212. 2007.
Herbs glandular puberulent throughout, more densely so on distal parts, sometimes also sparsely strigillose on ovaries and leaves. Leaves 0.3–4 × 0.04–0.3(–0.4) cm, fascicles of small leaves to 1.5 cm often present in axils; blade filiform to narrowly lanceolate, base attenuate, margins entire or remotely serrulate, sometimes undulate. Flowers: buds with free tips 0.5–4 mm; floral tube 16–50 mm; sepals 7–17 mm; petals 12–23 mm; filaments 6–13 mm, anthers 6–11 mm; style 26–60 mm. 2n = 14.
Phenology: Flowering May–Oct.
Habitat: Highly local, often abundant, almost always on semiarid gypsum flats, dunes, or outcrops, with Juniperus, Larrea, and Yucca.
Elevation: 600–1900 m.
N.Mex., Tex., Mexico (Chihuahua, Coahuila, Zacatecas).
Subspecies filifolia occurs in Otero and Torrance counties in southeastern New Mexico, south and east through the Trans-Pecos and southern Panhandle of Texas to Cottle County in Texas, and southward from widely scattered localities in central Chihuahua, Coahuila, and Zacatecas, Mexico.