Anemonella Spach is a monotypic genus in the family Ranunculaceae, containing the single species Anemonella thalictroides (L.) Spach, commonly known as rue-anemone or windflower. The genus is native to eastern North America. Many modern treatments—supported by molecular evidence—subsume this species into the large genus Thalictrum, where it is known as Thalictrum thalictroides (L.) A.J.Eames & B.Boivin, though the name Anemonella is still retained by some authorities.
The plant is a delicate, hairless herbaceous perennial growing 10 to 30 cm tall from a cluster of tuberous roots. Its basal leaves are two-times ternately compound with widely rounded, shallowly three-lobed leaflets that closely resemble the foliage of meadow rue (Thalictrum). In spring, flowers are borne singly or in small umbel-like clusters of three to six above a whorl of leaf-like involucral bracts. Each flower consists of five to ten showy, petal-like sepals in white to pale pinkish-lilac surrounding a central group of numerous yellow stamens and four to fifteen carpels. Fruits are small ovoid achenes, 3 to 4.5 mm long, prominently ribbed, maturing from green to dark brown.
The genus was established by Édouard Spach in 1839 to accommodate a single species originally placed in Anemone by Linnaeus in 1753. Spach considered the plant's diminutive stature, umbelliform inflorescence, and tuberous roots sufficiently distinctive to warrant a separate genus, despite its leaf resemblance to Thalictrum. The common name "rue-anemone" reflects this dual affinity. Anemonella thalictroides is sometimes confused with the false rue-anemone (Enemion biternatum), which also bears white spring flowers in woodland, but differs in always having five sepals, flowers held in leaf axils, and deeply cleft leaves.
Etymology
The genus name Anemonella is a diminutive of Anemone, reflecting its close resemblance to that genus and its small size. The specific epithet thalictroides means "resembling Thalictrum" (meadow rue), referring to the similar pinnately compound leaves.
Distribution
Anemonella thalictroides is native to the northeastern United States and Ontario, Canada. It inhabits banks and thickets in low-lying deciduous woodland, typically at elevations from sea level to 300 m.
Ecology
Rue-anemone blooms in early spring in deciduous woodland understories, favouring banks and thickets. It grows singly on wooded slopes rather than forming large colonies.
Taxonomy Notes
Anemonella was established by Édouard Spach in 1839 for a single species previously placed in Anemone by Linnaeus (1753). Bernard Boivin transferred it to Thalictrum in 1957, and molecular phylogenetic studies support this placement. Some authorities (including The Plant List) retain Anemonella as a distinct genus; others treat the species as Thalictrum thalictroides.
