The Evening Primrose or Willow herb family - Onagraceae - comprises about 20 genera and 700 species of annual or perennial plants that live throughout the world. They are mainly herbs, but we also find trees and shrubs. Some genera such as Fuchsia or Oenothera are very valuable in gardening. Most species are found in temperate regions of the New World.
The flowers of this family are usually radially symmetrical, has 4 petals and 4 sepals, mostly separate, and growing in tall or branched clusters. The flower parts are attached at the top of the ovary. Number of stamens are 4 to 8, generally 8 and the pistil is single with a 4-lobed stigma in many cases.
The plants have leaves that are simple, alternate or opposite, without stipules.
The fruits are commonly contained in an long 4-chambered capsule and carry a white tuft of hair for wind dispersal.