Stems erect, 20-50 cm, glabrous, from rhizomes. Leaves basal and cauline; cauline 1-3, those proximal to inflorescence petiolate, those subtending panicle branches sessile. Leaf blade 3-4×-ternately compound; leaflets obovate to orbiculate, apically 3-5-lobed, 5-20 mm, lobe margins crenate, surfaces abaxially glabrous or glandular-puberulent. Inflorescences terminal, panicles, narrow and dense, many flowered. Flowers: sepals greenish white, lanceolate or broadly ovate to elliptic or obovate, 2-4 mm; filaments colored, not white, (1.8-)3-5.5 mm; anthers 2-3.5 mm, blunt to mucronate; stigma commonly yellowish. Achenes 5-17, erect to spreading, not reflexed, nearly sessile; stipe 0.1-0.3 mm; body often distinctly curved, elliptic-oblong, nearly terete to slightly flattened, adaxial surface 3-4(-6) mm, glabrous to glandular, veins distinct, not anastomosing-reticulate; beak 1.5-2.5(-3) mm. Flowering early summer-mid summer (Jun-Aug). Prairies, riparian woods, and coniferous, deciduous, and mixed forests; 600-3700 m; Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon; Colo., Idaho, Minn., Mont., Nebr., Nev., N.Mex., N.Dak., Oreg., S.Dak., Utah, Wash., Wis., Wyo. Thalctrum venulosum is similar to T . confine and T . occidentale . Careful field studies are needed to clarify the relationships among these taxa.
Stems glabrous or nearly so, arising 3-10+ dm from the upturned end of a rhizome; lvs usually at least sparsely glandular beneath, but less so than in no. 8 [Thalictrum revolutum DC.], those below the infl petioled, those subtending the panicle-branches sessile; panicle with ascending branches; body of the achene 4-6 mm, its lower margin more convex than the upper; 2n=42. Rocky or gravelly soil, often along shores; Lab. to B.C., s. to Vt., n. N.Y., n. Mich., n. Wis., n. Minn., Wyo., and Oreg. June, July. Our plants have been distinguished on dubious grounds from typical cordilleran T. venulosum as var. confine (Fernald) B. Boivin. (T. confine)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.