Sparingly branched, 3-8 dm, glabrous or nearly so; basal lvs simple, broadly ovate, usually cordate at base, or occasionally ternate like the cauline; cauline lvs ordinarily pinnate with 3(5) ovate or lanceolate, toothed lfls 4-8 cm, rarely the lateral lfls again 2-3-lobed; umbels long-peduncled, 3-8 cm wide, the 6-10 rays unequal; fr ellipsoid, 3.5-5 mm, three-fourths as wide, including the broad wings; 2n=22. Woods, R.I. to Minn. and S.D., s. to Ga., La., and Okla. May, June. Typical T. trifoliatum (T. atropurpureum), with dark purple fls, is widespread, but more common eastward. Yellow-fld plants, usually distinguished as var. flavum S. F. Blake (T. aureum, misapplied), are also widespread, but more common westward.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Frequent in woodland throughout the state. Usually restricted to wooded slopes along or near streams. It is to be noted that all Indiana specimens have yellow flowers.
Indiana Coefficient of Conservatism: C = 5
Wetland Indicator Status: UPL
Diagnostic Traits: perennial to ca. 0.6 m tall; basal leaves simple, cordate, rotund; cauline leaves ternate or simple; nodes glabrous to minutely pubescent; umbel bracts lacking or minute; flowers yellow; fruits ellipsoid, ca. 4 mm long, with prominent winged ribs.