Evening Primrose

Evening Primrose

Oenothera biennis

Botanical Family: Onagraceae (Willowherb family)

Botanical Description

Oenothera biennis is a striking biennial growing 1-2 meters tall in the second year. First-year plants form a rosette of lance-shaped leaves. The second-year flower stalk bears large, fragrant, lemon-yellow flowers that open at dusk and fade by morning – perfect for night-flying moth pollinators. The small seeds are the primary commercial source of the valuable oil.

Medicinal Actions

Seed oil: Anti-inflammatory, supports skin and hormone balance.

Whole plant: Astringent, sedative, antispasmodic.

Traditional uses: Native American tribes used the whole plant for bruises, wounds, and skin problems. Modern use focuses on the seed oil, which is rich in gamma-linolenic acid (GLA) – an essential fatty acid the body needs for prostaglandin production.

Modern research: GLA has been studied for eczema, PMS, diabetic neuropathy, and rheumatoid arthritis with mixed but promising results.

Body Systems Affected

Integumentary: GLA supports skin health; used for eczema and dry skin conditions.

Reproductive: Traditionally used for PMS and menopausal symptoms.

Nervous: GLA supports nerve health; studied for diabetic neuropathy.

Musculoskeletal: Anti-inflammatory effects may help with arthritis.

Safety Information

Generally safe for most people.

Bleeding disorders: May increase bleeding risk. Avoid before surgery.

Seizure disorders: Some concern about lowering seizure threshold.

Pregnancy: Traditionally used in late pregnancy to prepare for labor. Consult a practitioner.

Growing Guide

Hardiness: Zones 3-9. Very adaptable.

Light: Full sun to partial shade.

Soil: Well-drained, sandy or average soil. Tolerates poor conditions.

Sowing: Sow in autumn or early spring. Seeds need cold to germinate well.

Spacing: 30-45cm apart.

Harvesting

Root: Harvest first-year roots in autumn (traditionally eaten as vegetable).

Leaves: Young leaves edible.

Seeds: Collect when pods are dry but before they split.

Drying & Storage

Dry seed pods completely before threshing. Seeds can be cold-pressed for oil (requires significant quantity and equipment) or ground for use. Store seeds in refrigerator to prevent rancidity. Oil must be kept refrigerated and used within several months.