The plant is a perennial herb with an erect, hairy stem bearing alternate, rough, hairy, lanceolate leaves. The leaves taper to a point and grow from 3 - 6 inches long.
Fruit is an oblong, hairy capsule.
The normal diet is quite sufficient in linoleic acid, but the first step in its conversion to prostaglandin E1 can be easily blocked. Dietary GLA could therefore be extremely valuable since very few factors block the successive steps in the metabolic pathway. Most, if not all, properties of evening primrose oil resemble and indeed can be attributed to the actions of prostaglandin E1. The only two symptoms which persisted in more than half of the women were tiredness and headaches. A dosage of four 500mg capsules was recommended morning and night for two weeks leading up to menstruation.