Phenology of evening primrose

Oenothera are the evening primroses, or sundrops, and are so named for their tendency to open cheery, long-lasting yellow flowers during the evening. There are about 145 species of evening primrose spread across the New World, where they have long be a cultivated species. One species, Oenothera biennis, is common across eastern and central North America, and has a long history of medicinal use. Much of the plant is edible and the oil for primrose has long been used a traditional medicine.

Evening primose plants (white flowers) are often dominant in sandy areas. Photo by mwdenslow

Evening primrose is pollinated by a special set of bee and moth pollinators with specialized ability to handle its more viscous pollen strands, and its seeds are eaten by birds such as finches. Evening primroses are not related to other primroses in the genus Primula, which are in a different family.  

While diurnal patterns of flower opening and closing is a form of phenology, we are interested here in the seasonal patterns of evening primrose blooming, and especially if climatic changes are impacting evening primrose cycles. We are especially interested in both spring and fall timing since many in this species can have two generation of plants per year.  

We are really excited to launch the Evening Primrose Phenology project as out first truly mobile-friendly Notes from Nature project. We are just looking for help with documenting flower presence, so a simple “yes it has flowers” or “no it doesn’t” suffices.

Its so easy to try one – we hope you do!