Description from Flora of China
Arctanthemum (Tzvelev) Tzvelev; Dendranthema (Candolle) Des Moulins; Dendranthema sect. Arctanthemum Tzvelev; Pyrethrum sect. Dendranthema Candolle.
Subshrubs or perennial herbs; indumentum absent or of basifixed or medifixed hairs. Leaves alternate, pinnately or palmately divided, serrate, or rarely entire. Synflorescence a lax irregular terminal cyme, often reduced to solitary capitulum. Capitula heterogamous, radiate, laxly corymbose or solitary. Involucres cup-shaped, rarely campanulate; phyllaries in 4 or 5 rows, scarious margin white, brown, or dark brown, or outer and middle ones herbaceous and pinnatilobed or pinnatifid. Receptacle convex to conical, epaleate. Ray florets female, fertile, in 1 or many rows (in cultivars); lamina yellow, white, or red. Disk florets many, bisexual, fertile; corolla yellow, tubular, 5-lobed. Anther obtuse at base; apical appendage lanceolate-ovate or narrowly elliptic. Achenes subterete or obovoid, faintly 5-8-ribbed. Pappus absent.
The florists’ chrysanthemum, 菊花 (ju hua), is an enormous hybrid complex developed over many centuries (a Chinese account published in 1630 listed over 500 cultivars) into the huge array of ornamental cultivars available today. The primary parental species is Chrysanthemum indicum, but the other parentage is now obscure. More recent hardier "Korean chrysanthemums" include C. zawadskii in their parentage. This complex is most widely known as "C. grandiflorum" (Broussonet, Elench. Horti Bot. Monspel. 15. 1805, supposedly based on Anthemis grandiflora Ramatuelle, J. Hist. Nat. 2: 233. 1792), but Broussonet’s name is a nomen nudum with no reference to Ramatuelle’s name; and, even if it were validly published, it would be a later homonym of C. grandiflorum (Desfontaines) Dumont de Courset (Bot. Cult. 2: 467. 1802). The most common alternative name is C. morifolium Ramatuelle (loc. cit.: 240), but this is of uncertain status and identity. Further work is therefore needed to establish the most acceptable scientific name for the complex. As is to be expected for such an important horticultural plant, there is an extensive synonymy, including: A. apiifolia R. Brown, A. artemisiifolia Willdenow, A. stipulacea Moench, C. hortorum L. H. Bailey, ?C. morifolium var. gracile Hemsley, C. sinense Sabine, C. sinense var. hortense Makino ex Matsumura, C. stipulaceum (Moench) W. Wight, Dendranthema grandiflorum (Ramatuelle) Kitamura, D. morifolium (Ramatuelle) Tzvelev, D. sinense (Sabine) Des Moulins, and Matricaria morifolia Ramatuelle.
Thirty-seven species: mostly in temperate Asia; 22 species (13 endemic) in China.
(Authors: Shi Zhu (石铸 Shih Chu); Christopher J. Humphries, Michael G. Gilbert)