Evening Primrose, Oenothera
Easily grown in average, medium moisture, well-drained soils in full sun. Tolerates some part afternoon shade and some drought. Grows well in gravelly or sandy soils. May spread in the landscape by self-seeding.
Oenothera biennis, commonly known as evening primrose,
An upright, rough-hairy, purple-tinged flower stem (usually a single stem but sometimes multiple stems) with spirally arranged leaves rises from the center of the rosette to 3-5’ tall, topped by a showy summer to fall (June to September) bloom of bowl-shaped, four-petaled, lemon yellow flowers (each to 1-2” across). Flowers bloom in a multi-flowered terminal panicle and, if present, in panicles at the tips of major stems, with a single flower blooming at the base of upper leaf-like bracts. Flowers open at dusk and close again in the morning when hit by sun, hence the common name of evening primrose. Flowers are fertilized by night-flying moths which are attracted by the mild lemon flower fragrance and by bees in the early morning before closure. Each flower has 4 petals, 4 reflexed sepals, 8 stamens and a prominent style with a cross-shaped stigma. Fruits are capsules (narrow seed pods to 1 1/2” long) which split open when ripe to release numerous seeds (to 100 seeds per capsule). Plants die after setting seed, but will remain in the landscape through self-seeding.
Seed oil (plant seeds contain gamma-linolenic acid) has been used in a number of different medicinal applications (particularly in Europe) since the 1600s as reflected in the sometimes used common names of King’s Cure-All and Fever-Plant. Evening primrose oil is now commercially cultivated in 15 countries. All parts of this plant including the roots were once used as food by American Indians.
No serious insect or disease problems. Leaf spot and powdery mildew may occur, leave air space around plants for ventilation.
Yellow color is striking. Use in beds and borders. Wildflower gardens. Cottage gardens. Herb gardens.