Circaea, commonly known as enchanter's nightshades, is a genus of perennial herbaceous flowering plants belonging to the family Onagraceae (the evening primrose family), within the order Myrtales. About two dozen taxa have been described, of which eight are accepted as species.
Plants in the genus bear erect stems that may or may not branch. The stem leaves are opposite and stalked (petiolate), with toothed (dentate) margins. Flowers are borne in terminal, erect racemes and are distinctively dimerous — each flower has 2 sepals, 2 petals, and 2 stamens, arranged so the stamens align with the sepals. The petals are white or pink. The fruit is a small capsule containing one or two seeds; dispersal is achieved by hooked burrs that cling to fur, feathers, and clothing.
The genus is distributed across the temperate and boreal forests of the Northern Hemisphere, from near sea level up to 5,000 metres altitude and from approximately 10° to 70° North latitude. Circaea alpina is the most widespread member, occurring across North America, Europe, and Asia. Circaea lutetiana ranges throughout Europe eastward to Iran.
The genus was established by the Swedish botanist Carl Linnaeus in 1753, when he described two founding species: Circaea lutetiana and Circaea alpina. Molecular phylogenetic evidence indicates the closest living relatives of Circaea are the ancestors of the genus Fuchsia, from which it diverged roughly 41 million years ago.
Etymology
The genus name Circaea derives from Circe (Kirkē), the enchantress of Greek mythology. Botanists in the late 16th century believed Circe used the plant as a magical charm to transform Odysseus's companions, giving rise to the common name "enchanter's nightshade." The name has no connection to the unrelated nightshade family (Solanaceae).
Distribution
Circaea species grow throughout temperate and boreal forests of the Northern Hemisphere, spanning latitudes of roughly 10°–70° N and altitudes from sea level to 5,000 metres. The most wide-ranging species, Circaea alpina, occurs across North America, Europe, and Asia. Circaea canadensis is found in North America, European Russia, and Asia, while Circaea lutetiana is broadly European, extending east to Iran.
Taxonomy
Carl Linnaeus founded the genus in 1753 with the descriptions of Circaea lutetiana and Circaea alpina; he also described a variety of C. lutetiana that later became Circaea canadensis. As of 2022, Plants of the World Online recognises eight species and eight subspecies, plus eight named hybrids. Molecular evidence places Circaea as sister to the Fuchsia lineage within Onagraceae, with divergence estimated at approximately 41 million years ago.
