Evening primrose is a member of the “Oenothera” genus within the Evening Primrose Family, a widely distributed group that contains fuchsia and water chestnut. In the southern mountains, five genera within that family are represented, containing familiar plants like enchanter’s nightshade and seedbox, as well as less familiar ones like biennial gaura and willow herb.
Here in the westernmost counties of North Carolina, there are three native species belonging to the “Oenothera” genus. First, of course, there’s the common evening primrose (O. biennis), which blooms from June into October, displaying buttery-yellow, lemon-scented flowers one to two inches in width.
Cut-leaved primrose (O. laciniata) is a scrubbier species with smaller flowers and deeply lobed leaves that is usually encountered in waste places.
Even showier than common evening primrose, however, is the species called sundrops (O. fruticosa), which displays large flowers during daylight hours from May into August. There are several recognized forms of sundrops, but most current accounts cite them as a single species.
In addition to these native species, showy evening primrose (O. speciosa) — a large-flowered species native to the central U.S. that displays petals ranging from white to pink to lavender — has escaped in certain areas along roadsides and in fields to take up residence here in Western North Carolina.
Sundrops are very showy, display their flowers during the daylight hours, and provide an ongoing staple in perennial beds. Accordingly, it’s the species traditionally favored by gardeners. But with the growing interest in wildflower meadows and other highly diversified settings featuring native plants, common evening primrose and its evening-blooming cultivars are gaining in popularity.
The plant’s internal clock opens its flowers in early evening so as to attract pollinators like the pink night moth and sphinx moths. These insects are apparently attracted by the yellow color of the petals. It was once theorized that these structures are unusually visible at night because they are slightly phosphorescent and able to produce, as it were, their own light. The late 19th century botanist Charles Millspaugh refined that theory by pointing out that the petals don’t actually produce their own light but merely “store” sunlight during the daylight hours. He compared the process to the one whereby calcium sulfide, obtained from crushed oysters, was used at the time for luminous clock faces.
In an article that appeared in “Horticulture” magazine, Carol Bishop Hipps provided an evocative description of evening primrose in action:
“Watching an evening primrose bloom rekindles one’s sense of wonder. As fireflies drift aloft in the summer twilight, a tightly rolled up flower bud shaped like an okra pod begins to swell until it resembles a small yellow cigar. Suddenly the sepals flick back, the ghostly pale petals begin to spring apart, and the eight stamens and the cross-shaped stigma writhe into position. Bud after bud perceptively stirs, then flares open in a performance reminiscent of time-lapse photography. A rich fragrance fills the air, summoning night-flying moths, some of which hover like hummingbirds above the fragile, cup-shaped blossoms, probing for nectar.”