Evening primrose is a North American native biennial. The first year it produces a rosette of low-growing leaves. The second  year it spikes and flowers, produces seed, and dies.

Oenothera biennis is known for the oil which is produced from its seeds. Evening primrose oil is a rich source of the omega 6 gamma-linolenic acid (GLA), an essential fatty acid. Health benefits attributed to evening primrose are largely due to its GLA content. GLA helps prevent high blood pressure, hardening of the arteries, eczema, heart disease, rheumatoid arthritis, and multiple sclerosis. It improves circulation, and reduces inflammatory autoimmune reactions. Although it has numerous vital functions, the body is unable to produce it and must get it from food sources.

Due to its positive effect on hormone response, EPO (evening primrose oil) is known to be helpful for PMS and menopause. When taken every day, it is shown to eliminate many issues related  to PMS, such as irritability, depression, bloating, and breast pain. For this purpose, it is recommended to take up to 3000 mg daily.

As an antispasmodic, evening primrose is useful for asthma and cough.  It has a beneficial effect on the liver, and a relaxing effect on the nervous system and muscles. This makes it beneficial for the treatment of anxiety, and menstrual cramps. It has shown promise for lifting depression, especially where when it is related to exhaustion or addiction withdrawal, issues with the GI tract, or when it is hormonally oriented.

A tea, made from the whole plant, is relaxing, and antispasmodic. It is slightly astringent and mucilaginous, and soothing to the stomach. It is also nourishing to the skin when used externally.

The root is both edible and medicinal. The root or the whole plant can be dried and ground into a powder, mixed with warm honey, and taken for sore throat and cough (also see plantain).

The leaves can be used as a poultice for insect bites and stings, wounds, and bruises. (also see plantain and yarrow)

The whole plant is edible. The leaves have a slightly peppery flavor and can be added to salads and stews. They are a great source of quercetin. The first year root is best harvested in the spring, and can be eaten raw, boiled, or roasted. The flowers are tasty in a salad. Even the green seed pods can be roasted and eaten. The seeds are a great source of tryptophan, the precursor to serotonin, a brain chemical that improves mood.