Oenothera biennis, Common Evening Primrose

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Common Evening Primrose, as its name implies, is a night blooming flower. The flowers close as noon arrives, and bloom again in the evening. When grown in the right conditions, it can be beautiful, gracing the summer garden with profuse yellow blooms. However, it can also survive in very poor conditions where it is not nearly so attractive. Unlike many other primroses, it is usually fairly tall with the flower clusters blooming at the top of a rough-leaved stalk.

Cultivation

A Self-Seeding Biennial

Common Evening Primrose is an early colonizer of disturbed ground, thriving in “dry, rocky plains; disturbed areas; lake shores; open woods,” according to wildflower.org. “While this species spreads too aggressively to be the right fit for every landscape, it works particularly well in meadow-style plantings, paired with other tall and robust wildflowers like New England aster (Aster novae-angliae), common vervain (Verbena hastata), or goldenrods (Solidago spp.)” (Gallogly, September 2018, Uncovering the Beauty of a Roadside Flower.) As plant communities mature, this plant will eventually be outcompeted and fade from the landscape. But, how long does it remain in the seedbank?

This biennial grows a basal rosette in the first year, typically in the fall, which overwinters. Next spring, it sends up tall, stiff, leafy stalks topped with lemon yellow primrose flowers. The seed capsules are sticky and green, turning brown and splitting open to scatter the seeds at the end of the year. Though this signals the individual plant’s death, it is an effective and prolific self-seeder, tending to colonize patches, but perfectly capable of expanding its range across open ground and becoming a weed in the garden. Therefore, it is best cultivated in a patch where it can colonize and self-seed to renew the patch without disturbing other perennial beds.

If trimmed to 18″-24″ high in late spring (May or early June), it may be cultivated to bloom atop a lower mound, as the photo below shows.

Human Uses

Edible & Medicinal

Evening Primrose has a long history of use and is the source of Evening Primrose oil, a plant-based oil with many herbal uses. As a consequence, the majority of its Wikipedia article address agricultural topics. According to Wikipedia, “Most of the plant parts are edible, having a taste that is mild. The roots can be eaten raw or cooked like potatoes. The leaves can be eaten raw in salads or cooked like spinach or in soups. Anishinaabe tribes traditionally make tea from the evening primrose leaves for use as a dietary aid and to reduce fatigue.” Read more at Wikipedia.org.

Ecology

A Pioneer Specialist

Oenothera biennis’ primary pollinators are nectar-feeding moths by night, and native specialist bees who forage at night or in the morning. It is a host plant to the beautiful Primrose Moth (Schinia florida) and the White-Lined Sphinx Moth (Hyleas lineata). Bear in mind that if you’re looking forward to seeing these rare and beautiful moths after planting Evening Primrose, you might have to wait a few years for them to find you, or add other complementary plants to help them get established. Also, if you’re hosting a moth species, be prepared for the giant caterpillars! Big beautiful moths start out life as big dramatic caterpillars and you can’t have one without the other.

It is a Tallamy keystone species for native bees, but is unlikely to fulfill the needs of other generalist native bees because the flowers are not available during normal bee feeding times and the pollen is loosely held by viscin threads which requires specialized anatomy to collect. So, plant it because you want to support rare and unusual pollinators or because you need a vigorous meadow colinizer or because you love another one of this plant’s many virtues which include many human uses.