Evening Primrose Oil Looking like an oversized buttercup, evening primrose is actually a member of the willow family. It is so called because its light yellow flowers open as the sun goes down. This wild flower is native to North America but it is now widely grown all over Europe where it is a common sight in hedgerows. The plant and its root have been used for centuries to treat a variety of ailments including bruises, haemorrhoids, sore throats and stomach aches, but it wasn’t until the 1970s that its seed oil, which contains gamma linolenic acid (GLA), started to be recognised for its healing properties. The GLA in evening primrose oil is converted directly into anti-inflammatory prostaglandins, which account for most of its therapeutic effects.