Oenothera is a genus of flowering plants in family Onagraceae, comprising about 125 species. It is commonly known as Evening-Primrose, Suncups and Sundrops. Oenothera is native to North and South America.
Oenothera is either annual, biennial or perennial herbaceous plant. One of the most distinctive features of the flower is the stigma with four branches, forming an X shape. The flowers open in the evening, thus the name 'evening primrose' and the colors are mostly yellow, but there are a few species with white, purple, pink or red. The fragrant evening-primrose Oenothera caespitosa, a California species, are white at first then change to pink or light magenta. Pollination is by moths and bees. Onethera species are food plants for larvae of some Lepidoptera species including Schinia felicitata and Schinia floorida.
The seeds of Oenethera ripen from late summer to fall. Mature seeds contain 7-10% gamma-linolenic acid, a rare essential fatty acid. The oil also cantains around 70% linoleic acid. The Oenothera biennis seed oil is used to reduce the pains of Premenstrual Stress Syndrome.
Evening Primrose are popular ornamental plants in gardens. Plant Evening Primrose in wildlife garden to attract warblers, which feed on the insects attracted to the flowers. The tiny seeds in fruit capsules are eaten by finches and siskins. Plant Oenothera in sun or partial shade, in fertile and moisture-retentive soil. Propagation is by division in late spring. Pests are slugs and snails.