Oenothera biennis

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common evening primrose
Oenothera biennis 20050825 962.jpg
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Myrtales
Family: Onagraceae
Genus: Oenothera
Species: O. biennis
Binomial name
Oenothera biennis
L.

Oenothera biennis (common evening primrose, evening star, or sun drop) is a species of Oenothera native to eastern and central North America, from Newfoundland west to Alberta, southeast to Florida, and southwest to Texas, and widely naturalized elsewhere in temperate and subtropical regions.[1] Evening primrose oil is produced from the plant.[2][3]

Growth and flowering[edit]

Oenothera biennis has a life span of two years (biennial) growing to 30–150 cm (12–59 in) tall. The leaves are lanceolate, 5–20 cm (2.0–7.9 in) long and 1–2.5 cm (0.39–0.98 in) broad, produced in a tight rosette the first year, and spirally on a stem the second year.

Blooming lasts from late spring to late summer. The flowers are hermaphrodite, produced on a tall spike and only last until the following noon. They open visibly fast every evening producing an interesting spectacle, hence the name "evening primrose."

The blooms are yellow, 2.5–5 cm (0.98–1.97 in) diameter, with four bilobed petals. The flower structure has an invisible to the naked eye bright nectar guide pattern. This pattern is apparent under ultraviolet light and visible to its pollinators, moths, butterflies, and bees.

The fruit is a capsule 2–4 cm (0.79–1.57 in) long and 4–6 mm (0.16–0.24 in) broad, containing numerous 1–2 mm (0.039–0.079 in) long seeds, released when the capsule splits into four sections at maturity.[4][5][6][7]

Synonym[edit]

It is also known as Weedy evening-primrose, German rampion, hog weed, King's cure-all, and fever-plant.[8]

Cultivation and uses[edit]

The mature seeds contain approximately 7–10% gamma-linolenic acid, an essential fatty acid. The O. biennis seed oil is used to reduce the pains of premenstrual stress syndrome and is beneficial to the skin of the face.[citation needed] Also, poultices containing O. biennis were at one time used to ease bruises and speed wound healing[citation needed].

Its leaves are edible and traditionally were used as a leaf vegetable.[9]

Evening primrose is sometimes used to treat eczema. Natural Standard has given evening primrose oil a "B" score for the treatment of eczema; meaning there is good scientific evidence supporting its use.[10] The symptoms of eczema can be exacerbated due to scratching and drying out the skin. Evening primrose oil contains linoleic acid, which is the primary oil found in the stratum corneum.[11] Supplementation with EPO may help rehydrate skin that has been scratched due to eczema. Furthermore, gamma-linoleic acid is metabolized into anti-inflammatory compounds, which may contribute to its ability to provide symptomatic relief in eczema. Most studies evaluating the effectiveness of EPO used 4 capsules of standardized extract (~1600 mg of evening primrose oil TOTAL) dosed by mouth twice daily for up to 12 weeks.

Evening Primrose Oil has been shown to slightly reduce blood pressure, can increase clotting time (use with caution if you take warfarin or aspirin), and should not be used by epileptics as it lowers the seizure threshold. Safety has not been evaluated in pregnant or nursing women.

References[edit]

External links[edit]