Circaea

Circaea
The Circaea, or enchanter's nightshades, are a genus of flowering plants in the evening primrose family Onagraceae. About two dozen taxa have been described, including eight species. Plants of the genus occur throughout the temperate and boreal forests of the Northern Hemisphere. Three taxa occur in North America: Circaea alpina, Circaea canadensis, and the hybrid Circaea × sterilis. The generic name Circaea refers to the enchantress Circe from Greek mythology who is said to have used the herb as a charm.
Description
Members of genus Circaea are perennial, herbaceous plants with erect stems, which may or may not be branched. The stem leaves are opposite and petiolate, with toothed edges (i.e., with dentate leaf margins). The inflorescence is a terminal, erect raceme, with additional racemes at the apices of stem branches (if any). Flowers are dimerous with 2 sepals, 2 petals, and 2 stamens. The sepals, petals, and stamens alternate such that the stamens ultimately align with the sepals. The petals are white or pink in color. The fruit is a capsule with one or two seeds. Plants disperse their seeds by producing burrs that adhere to clothing, fur, and feathers.
Taxonomy
In 1753, Swedish botanist Carl Linnaeus established the genus Circaea by describing two species, Circaea lutetiana and Circaea alpina. Linnaeus also described a variety of C. lutetiana, which later became known as Circaea canadensis.
The generic name Circaea refers to the enchantress Circe from Greek mythology. Botanists in the late 16th century believed Circe used the herb to charm Odysseus' companions, hence the common name enchanter's nightshade (not to be confused with the nightshade family of plants, which are unrelated). Molecular evidence indicates the closest relative to Circaea is the lineage that gave rise to the genus Fuchsia, which diverged from it around 41 million years ago.
Taxa
, Plants of the World Online (POWO) accepts eight species and eight subspecies:
Circaea alpina
Circaea alpina subsp. alpina
Circaea alpina subsp. angustifolia
Circaea alpina subsp. caulescens
Circaea alpina subsp. imaicola
Circaea alpina subsp. micrantha
Circaea alpina subsp. pacifica
Circaea canadensis
Circaea canadensis subsp. canadensis
Circaea canadensis subsp. quadrisulcata
Circaea cordata
Circaea erubescens
Circaea glabrescens
Circaea lutetiana
Circaea mollis
Circaea repens
POWO also recognizes eight named hybrids:
Circaea × decipiens
Circaea × dubia
Circaea × intermedia
Circaea × mentiens
Circaea × ovata
Circaea × skvortsovii
Circaea × sterilis
Circaea × taronensis
For example, the parents of Circaea × sterilis are C. alpina and C. canadensis. The hybrid is sterile but spreads vigorously by vegetative means.
Distribution
Members of genus Circaea occur throughout the temperate and boreal forests of the Northern Hemisphere, from near sea level to altitude, and from 10°–70° N latitude. Circaea alpina is the most widespread species, ranging across North America, Europe, and Asia. Likewise Circaea canadensis ranges across continents, in North America, European Russia, and Asia. Circaea lutetiana occurs throughout Europe, ranging eastward to Iran.
Three taxa are known to occur in North America: Circaea alpina, Circaea canadensis, and the hybrid Circaea × sterilis. C. alpina is wide ranging across the continent, from California to Alaska in the west, and from Newfoundland to North Carolina in the east, while C. canadensis is confined to the eastern half of North America. The hybrid, C. × sterilis, is found wherever the ranges of its parent species overlap.
References
External links
Natural England. Accessed July 2011
English Country Garden Accessed July 2011
Plant Identification UK Accessed July 2011
Taxa named by Joseph Pitton de Tournefort
Plants described in 1753
Taxa named by Carl Linnaeus
Onagraceae genera