Rudbeckia triloba L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Biennial or short-lived perennial 5–15 dm, moderately hirsute or strigose to subglabrous; lvs thin, sharply toothed to subentire, the basal ones broadly ovate or subcordate and long-petiolate, the cauline mostly narrower and shorter-petiolate or sessile, usually some of the larger ones deeply trilobed or seldom even pinnatifid; rays 6–13, yellow or orange, 1–2(–2.5) cm; disk dark purple or brown, hemispheric or ovoid, 8–15 mm wide; receptacular bracts glabrous, abruptly narrowed to a short but distinct awn-tip often shortly surpassing the disk-cors; pappus a minute crown; 2n=38, 57, the triploid more northeastern. Woods and moist soil; Conn. to Mich., Io., and Nebr., s. to Fla. and Tex. June– Oct. Most of our plants belong to the widespread var. triloba, with the lvs often (not always) well over 5 cm, some of them generally trilobed with the lobes generally acute, rarely any of them pinnately lobed. The var. pinnatiloba Torr. & A. Gray occurs on the Gulf coast of w. Fla. and disjunct in the Blue Ridge of N.C. and sw. Va. (where it has been called R. beadlei Small). It is a smaller and more delicate plant, with the lvs to 5(–8) cm, some of them generally pinnately few-lobed, the lobes often obtuse.