Calylophus tubiculus (A. Gray) P. H. Raven; Galpinsia tubicula (A. Gray) Small; Oenothera hartwegii Bentham var. tubicula (A. Gray) H. Léveillé

Subspecies 2 (1 in the flora): sw, sc United States, n Mexico.

H. F. Towner (1977) found that Oenothera tubicula is self-incompatible and diurnal with opening times just prior to sunrise. It occurs primarily on limestone soil in arid lowlands, but occasionally in montane areas, from Guadalupe County, New Mexico, south to western Texas, northeast to Howard County, Texas, and south to northern Zacatecas, south-central Nuevo León, and southwestern Tamaulipas, 600–1800 m. Subspecies strigulosa (Towner) W. L. Wagner & Hoch is known only from rocky, open sites and canyons in relatively montane areas, sometimes in pine forests in southernmost Coahuila, south-central Nuevo León, and southeastern Tamaulipas, from 1500 to 2300 m. It differs in being strigillose on the ovary and distally on stems, leaves linear to narrowly lanceolate, and the petals fading red or purple.

Lower Taxon

• Oenothera tubicula subsp. tubicula