Erect to spreading, hairy stems to 6–30 inches tall bear showy, yellow flowers in the upper leaf axils. Note the narrow, serrated leaves, and the distinctly keeled or ribbed sepals, buds, and seed capsules. The the disk-shaped stigma barely extends beyond the throat, allowing self-pollination.

FLOWER: April–July. Funnel-shaped, yellow flowers 3/8–1-inch wide (10–25 mm) with 4 crinkly, yellow petals; 4 sepals around the floral tube have ridged midribs and fold back away against the stem; flower bud is square with 4 sharp ridges; disk-shaped stigma is shorter than stamens; 8 stamens alternate long and short. Fruit capsule has 4 sharp ribs. Fruit is a narrow, cylindrical capsule 1/2–1 1/4-inches long (12–31 mm) with distinct ribs; surface covered with fine hairs.

LEAVES: Alternate. Blades narrow, linear to lance-shaped, 2-inches long (5 cm), margins often with widely separated small teeth. Leaves fold in the sun to conserve water.

HABITAT: Sandy, clay, gravelly soils, prairies, fields, dunes, roadsides; short grass prairie, pinion-juniper, ponderosa woodlands.

ELEVATION: 3,500-7,400 feet.

RANGE: AZ, CO, OK, KA, NM; widespread in states between the Mississippi River and Rocky Mountains.

SIMILAR SPECIES: The look-alike Square-bud Evening Primrose, O. berlandieri, has disk-like stigmas longer that stamens to enhance cross pollination.

NM COUNTIES: Widespread, except western counties, in low- to mid-elevation, dry habitats: Bernalillo, Chaves, Colfax, Curry, De Baca, Eddy, Guadalupe, Harding, Hidalgo, Lea, Lincoln, Mora, Quay, Rio Arriba, Roosevelt, San Juan, San Miguel, Santa Fe, Sierra, Socorro, Torrance, Union.