Distribution: Oenothera drummondii is subdivided into two subspecies, one of which occurs along a long stretch of the Atlantic coast and the other in a single small region of the Pacific coast of Baja California.
Habit: Erect to procumbent annual to perennial herbs from a taproots up to 2 cm in diameter, usually not forming rosettes but growing soon after germination from only a few basal leaves, non-flowering lateral branches often with a terminal rosette of crowded small leaves; stems 10-50 cm long, stiff, green, sometimes flushed with red, simple or much-branched, densely strigillose or sometimes also villous, becoming glandular-puberulent in upper part.
Leaves: Leaves basal and cauline, leaves and bracts grayish green, densely strigillose, rarely also glandular-puberulent, basal leaves 5-14 cm long, 1-2 cm wide, narrowly oblanceolate to elliptic, remotely shallowly dentate to almost entire, apex acute, gradually or abruptly narrowed to the petiole, cauline leaves 1-8 cm long, 0.5-2.5 cm wide, narrowly elliptic to broadly elliptic or narrowly obovate to broadly obovate, remotely shallowly dentate to subentire, rarely lyrate, apex acute to rounded, gradually or abruptly narrowed to the short petiole, bracts 0.8-5.5 cm long, 0.4-1.8 cm wide, narrowly elliptic to broadly elliptic or narrowly oblanceolate to oblanceolate, remotely and bluntly shallowly dentate to subentire, apex acute to obtuse, base narrowly cuneate to rounded, short-petiolate or sessile.
Flowers: Inflorecence lax, usually with lateral branches. Usually one flower per spike opening each day near sunset, floral tube 20-50 mm long, 1.5-2 mm in diameter, densely strigillose to villous, sometimes also scattered to sparsely glandular-puberulent, mature buds 5-11 mm in diameter at the base, narrowly lanceoloid or narrowly ovoid to ovoid, sepals 13-33 mm long, green to yellowish, often flushed with red and striped red at the margins, sometimes also red-maculate, pubescence like that of floral tube, free sepal tips 0.3-3 mm long, erect and appressed in bud, strigillose, petals 20-45 mm long, 25-55 mm wide, yellow, very broadly obovate, truncate to emarginate, staminal filaments 10-23 mm long, anthers 4-12 mm long, ovary 13-25 mm long, ca. 1.5 mm in diameter, densely strigillose to villous, sometimes also sparsely glandular-puberulent, style 35-75 mm long, the exserted part 15-35 mm long, stigma elevated above the anthers at anthesis, lobes 3-10 mm long.
Fruit: Capsule dehiscent 20-55 mm long, 2-5 mm in diameter, cylindrical, pubescence same as ovary, subterete, dehiscent nearly throughout capsule length, sessile.
Seeds: Seeds numerous, in 2 rows per locule, 1.1-2 mm long, 0.5-0.9 mm in diameter, ellipsoid to broadly ellipsoid, rarely suborbicular, brown, sometimes with darker flecks, the surface reticulate and regularly pitted.
Chromosomes: Chromosome number: n = 7 (7 bivalents*, ring of 4 and 5 bivalents* *, ring of 6 and 4 bivalents*** , or ring of 8 and 3 bivalents*** at meiotic metaphase I).
Notes: FNA, Self-compatible, modally outcrossing.