Evening Primrose Family

Farewell-to-Spring © TCorelli

Onagraceae (on-uh-GRAY-see-ee)

Iconic Features

    • Flower parts in fours
    • Inferior ovary
    • Often open at dawn or dusk

    Description (Jepson)

      • Annuals or herbaceous perennials
      • Eudicotyledons (eudicots) – a major lineage of flowering plants including most plants traditionally described as dicots and generally characterized by
        • 2 seed leaves (dicotyledon)
        • Netted (reticulate) leaf venation
        • Flower parts in fours and fives
        • Pollen grains with 3 pores (tricolpate)
        • Vascular bundles in stem arranged in a ring
        • Taproot system
      • Leaves
        • Generally simple (not divided into leaflets) and toothed
        • Alternate (1 leaf at each junction with stem), opposite (2 leaves at each junction with stem), or whorled (3 or more leaves at each junction with stem)
      • Flowers
        • Usually bisexual and radially symmetric
        • In parts of 4, with 4 petals and 4 sepals (usually green, outer flower parts)
          • Sepals generally fold back (reflex)
        • Pollen has cobweb-like (viscin) threads
          • Mining bees (Andrenidae family) and digger bees (Apidae family) are examples of bees that have evolved specialized hairs to transport the sticky pollen (Thorp 1979 and Grissell 2010)
          • Pollen with viscin threads has been found in only two other unrelated plant families: in some members of the Heath family (Ericaceae), including Rhododendron, and of the Pea family (Fabaceae); this is an example of convergent evolution (Sarwar 2007)
        • Ovary inferior (below the attachment of other flower parts)
          • Floral tube (hypanthium), which surrounds the ovary, is usually lengthened between the ovary and other flower parts
        • Often open at dawn or dusk
          • This process is an example of nyctinasty, which refers to diurnal and nocturnal changes (single or repetitive) exhibited by the leaves and flowers of some plants (van Doorn and van Meeteren 2003)
      • Fruit usually a capsule (dry, multi-chambered pod that splits open) with many small seeds


        • Approximately 657 species worldwide, in a wide range of habitats
          • Found in California from coastal dunes to alpine regions and in deserts and wetlands
          • Includes clarkias, suncups, willowherbs, and fuschias
        • Scientific name from the genus Onagra (now Oenothera), from the Greek for “(food of) the ass”
        • Distinct from the similarly-named Primrose family (Primulaceae), which includes the common ornamental primrose and shooting stars
        • Represented by 10 species at Edgewood

        See General References

        Specific References

          Grissell, E. 2010. Bees, Wasps, and Ants: The Indispensable Role of Hymenoptera in Gardens. Timber Press, Portland, Oregon.

            Sarwar, A.K.M. 2007, Mar. Pollen Morphology and Its Systematic Significance in the Ericaceae. Dissertation. Graduate School of Agriculture. Hokkaido University, Sapporo, Japan. p. 20.

              Thorp, R.W. 1979. Structural, Behavioral, and Physiological Adaptations of Bees (Apoidea) for Collecting Pollen. Annals of the Missouri Botanical Garden, 66(4), 788-812.

                van Doorn, W.G. and van Meeteren, U. 2003, Aug. 1. Flower Opening and Closure: A Review. Journal of Experimental Botany, 54: 389, pp.1801–1812.

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