Helianthus x laetiflorus Pers.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Much like H. pauciflorus var. pauciflorus, but with yellow disk; lvs often larger and with much longer (to 5 cm) petiole; invol bracts avg a little narrower, generally (2–) 2.5–4 mm wide, less imbricate, more pointed, and occasionally sparsely short-hairy on the back; 2n=102. Roadsides and other disturbed sites, mainly or wholly as an escape from cult., often ± sterile; scattered in e. and midwestern U.S. Aug., Sept. Thought to consist of hybrids and hybrid progeny of H. pauciflorus var. subrhomboideus and H. tuberosus, perhaps mainly a cultigen.