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Riverbank Evening Primrose (Oenothera riparia): Grand Strand August 2023 Plant of the Month

Posted on by Tierney Rosenstock

Riverbank evening primrose (Oenothera riparia). Credit: Tierney Rosenstock

You may be quite familiar with evening primroses (genus Oenothera), as some species are quite common and often pop up without assistance in lawns, roadsides, and old fields. In fact, there are over ten species native to South Carolina and some are even considered “weeds”. However, one species you are unlikely to have seen is Oenothera riparia, the riverbank evening primrose or riverbank sundrops. Unlike the more common evening primroses, this species is quite rare in SC and is considered to be imperiled in the Carolinas and critically imperiled in Virginia. Riverbank evening primrose grows no where else in the world.

As the common name suggests, riverbank evening primrose is found growing in freshwater tidal marshes and freshwater tidal swamp forests. Plants require “wet-feet” and adventitious roots will even emerge along stems that are submerged. The species is a long-lived perennial with erect stems, growing up to three feet tall and freely branched. Leaves are alternate, 3-4 inches long by 2/5 inches wide. The bright yellow flowers are typical of the genus with four petals that are about 1 inch long each, putting on a display from June through September. Flowers are likely to be very attractive to various bee species. 

Due to the very specific habitat requirements, specifically fresh water, the threat of salt water intrusion from sea level rise makes the future survival of these species a concern. However, there are some recent efforts to introduce this species into cultivation for ex situ conservation and eventually public and home gardens. 

Next time you are kayaking in the tidal portions of the Waccamaw River keep an eye out for this beauty!

Further Reading: 

Riverbank Sundrop; The Journey Begins by Patrick McMillan

Vascular Plants of North Carolina