1. Caulophyllum giganteum (Farwell) Loconte & W. H. Blackwell, Phytologia. 49: 483. 1981.
Caulophyllum thalictroides (Linnaeus) Michaux var. giganteum Farwell, Rep. (Annual) Michigan Acad. Sci. 20: 178. 1918
Stems 2-7 dm. Leaves: 1st leaf (2-)3-ternate; 2d leaf (1-)2-ternate; leaflets 5-10 × 3-8 cm. Inflorescences with 4-18 flowers. Flowers: bracteoles 2-4 mm; sepals purple, red, brown, yellow, 6-9 × 1-4 mm, laterally revolute; petals 2-3 mm; stamen filaments 1.5-2.5 mm; pistil 3-5 mm; style 1-2 mm. 2 n = 16.
Flowering early spring. Mesophytic forests; 0-700 m; Ont., Que.; Ky., Md., Mass., Mich., N.H., N.Y., N.C., Ohio, Pa., Tenn., Vt., Va., W.Va.
Caulophyllum giganteum has a relatively northern distribution, and it flowers precociously; C . thalictroides has a broader distribution, extending farther south, flowers and fruits later, and is less precocious. Caulophyllum giganteum is treated as part of C . thalictroides by most authors.