A native North American plant, evening primrose is also found in parts of the southern hemisphere as well as in Europe. The plant produces yellow flowers that only open up in the evening hours. In addition to flowers, the plant produces seeds. Evening primrose oil is extracted, using a cold pressed method, from the seeds of the plant. The oil can be placed into capsules to be used as a dietary supplement. The Latin name of this plant is Oenothera biennis.