Description from Flora of China
Eupatoriadelphus R. M. King & H. Robinson.
Herbs, annual to perennial. Leaves opposite or verticillate, upper leaves subopposite to alternate; blade linear to ovate, deltate, or 3-lobed, serrate to subentire. Synflorescence a corymbose or pyramidal panicle. Phyllaries 10-22, weakly to strongly subimbricate, 2-5-seriate, sometimes inner phyllaries deciduous; receptacle flat or weakly convex. Florets 3-23; corollas white to purple, lavender, or pink, narrowly funnelform or with constricted basal tube and narrowly to broadly campanulate limb, outer surface with glands often concentrated at base of throat and on outer surfaces of lobes, rarely with a few hairs; lobes 5, usually slightly longer than wide; antheropodium cylindric; anther appendages large, ovate-triangular, ca. 1.5 × as long as wide; style base puberulent or rarely glabrous, with or without node; style branches filiform to slightly broadened or flattened distally, papillose. Achenes prismatic, 5-ribbed; carpopodium not or slightly differentiated; pappus setae 25-40, barbellate, persistent, apical cells with rounded to shortly acute tips. x = 10, 20.
The results of the studies by G. J. Schmidt & E. E. Schilling (Amer. J. Bot. 87: 716-726. 2000) and those of M. Ito et al. (J. Plant Res. 113: 79-89. 2000) are in conflict as to the re-recognition of Eupatoriadelphus. Schmidt and Schilling favor a distinct Eupatoriadelphus (= the "Eutrochium group") whereas Ito et al. imply that Eupatorium s.s. can be divided into three "morphological species groups," one of which is the "Eutrochium group." As there is still much confusion among the Chinese species of Eupatorium with both sexual and agamospermous species, the species here are simply arranged alphabetically. The presence of the hybrid E. ×tripartitum (Makino) Murata & H. Koyama (E. chinense × E. lindleyanum), a plant with tripartite leaves, has been recorded.
See Lamont, Mem. New York Bot. Gard. 72: 1-68. 1995.
Forty-five species: Asia, Europe, North America; 14 species (six endemic) in China.