Duration: Perennial
Nativity: Native
Lifeform: Forb/Herb
General: Perennial herb, 10-40 cm tall, from a woody caudex; stems woody near the base, ascending to suberect, sparingly to moderately branched.
Leaves: Alternate along the stems; sessile or nearly so; blades linear to oblong-lanceolate, 1-5 cm long and 0.5 mm to 1 cm wide, with smooth to minutely toothed edges; leaf surfaces glabrous, hairy, or glandular-hairy.
Flowers: Large, yellow, and showy, borne in the axils of upper leaves; opening in the afternoon or near sunset; base of flower is a long, tapering hypanthium 2-6 cm long; sepals 4 per flower, 8-18 mm long, yellowish with red blotches; petals 4 per flower, 1-3 cm long, yellow when fresh, drying red.
Fruits: Capsule long and curved, 1-4 cm long and 2-3 mm wide, tapering to the base; splitting open longitudinally along 4 suture lines to release 2 rows of seeds from each of the 4 chambers.
Ecology: Found in deserts, plains, and foothills, from 3,500-7,000 ft (1067-2134 m); flowers May-September.
Distribution: AZ, NM, OK, and TX; south to n MEX.
Notes: A showy yellow-flowered evening primrose. Look for the low sub-shrubby growth form; and the large flowers which have yellow petals that dry to a pinkish color, red-spotted sepals, and a long narrow tapering hypanthium below the sepals that looks a bit like a flower stalk but actually contains the ovary. Allred and Ivey (2012) recognize 3 subspecies in New Mexico; Subsp. pubescens grows in sandy and limestone soil and has long spreading hairs on the ovary and usually also on the stems and margins of the leaves. Subsp. fendleri grows in diverse habitats, including limestone and gypsum, has hairless stems and leaves, and the leaves are 2-4 mm wide or wider. Subsp. filifolia grows on gypsum and limestone outcrops, has gland-tipped hairs on the stems and often on the leaves as well, and the leaves are much narrower, 1 mm wide or less. Note that there has been some nomenclature shifting in this group over the years; it shifted back and forth between Oenothera and Calylophus over the years. Also, C. hartwegii traditionally included as varieties several taxa that were later split out, including C. lavandulifolia and C. toumeyi.
Ethnobotany: Unknown
Etymology: Calylophus is from Greek kalyx for calyx, and lophos, meaning crest; hartwegii is named for the German plant collector Karl Theodor Hartweg (1812-1871).
Synonyms: Oenothera hartwegii
Editor: AHazelton 2017
