Onagraceae: Evening-primrose Family — Clarkia
All members of the Evening-Primrose family have 4-petaled flowers, and many of them are showy. Despite the name, they do not necessarily bloom in the evening. There is a separate family called Primrose (Primulaceae).
Clarkia is a particularly attractive genus with a wide variety of flowers. Some are immediately recognizable, but others require careful attention to such details as whether the buds are upright or nodding, the size and shape of the fruits, whether the stamens are all of the same length, and whether the axis of the inflorescence is straight or recurved. The Four-spot or Winecup Clarkia (Clarkia purpurea subsp. quadrivulnera) deserves a special mention for the variability of its flowers.