Thalictrum thalictroides or Anemonella thalictroides, the rue anemone, is a herbaceous perennial native to woodland in eastern North America. It has white or pink flowers surrounded by a whorl of leaflets and blooms in spring.
Thalictrum thalictroides is a hairless plant growing from tuberous roots, with upright, 10-to-30 cm (4-to-12 in) tall stems that end with flowers. The basal leaves have petioles (leaf stalks) 10-30 centimetres (4-12 in) long and leaf blades that are two times ternately compound. The leaflets are widely rounded in shape and the ends are three lobed.
It flowers in spring and the flowers are borne singularly, or in umbel-like inflorescences with 3 to 6 flowers. The flowers have short stems that hold the fully opened flowers above the foliage. The involucral bracts have three leaflets like the leaves. The showy rounded flowers have 4-15 carpels surrounded by many yellow stamens in the middle, and a cup of 5 to 10 white to pinkish-lilac petal-like sepals. The sepals are about 5 to 18 mm (316 to 1116 in) long and the filaments 3-4 mm (18-316 in) long.
In late spring, 3-to-4.5 mm (18-to-316 in) long, ovoid to fusiform shaped fruits called achenes are released. The green achenes have 8 to 10 prominent veins and become dark brown when ripe.
Originally described as Anemone thalictroides by Linnaeus in 1753, it was transferred to a new, monospecific genus, Anemonella, by douard Spach in 1839. Although similar to plants in the genus Thalictrum, Sprach considered the diminutive size, umbelliform inflorescence, and tuberous roots of this species to be distinctive enough to designate a new genus. Bernard Boivin considered this distinction suspect, and transferred the species to the genus Thalictrum in 1957. Molecular evidence supports the placement of the species within Thalictrum, and this placement is accepted by several modern treatments, although The Plant List retains it in Anemonella.