Cosmos

Cavanilles

Icon. 1: 9, plate 14. 1791

Etymology: Greek kosmos, harmoniously ordered universe, or kosmo, ornament
Treatment appears in FNA Volume 21. Treatment on page 203. Mentioned on page 184.
Annuals [perennials or subshrubs], 30–250 cm. Stems usually 1, erect or ascending, branched distally or ± throughout. Leaves mostly cauline; opposite; petiolate or sessile; blades usually 1–3-pinnately lobed [undivided], ultimate margins usually entire, faces usually glabrous, sometimes glabrate, hispid, puberulent, or scabridulous. Heads radiate, borne singly or in corymbiform arrays. Calyculi of [5–]8 basally connate, ± linear to subulate, herbaceous (striate) bractlets. Involucres hemispheric or subhemispheric [cylindric], 3–15 mm diam. Phyllaries persistent, [5–]8 in ± 2 series, distinct, lanceolate, lance-oblong, lance-ovate, or oblong, ± equal, membranous or herbaceous, margins ± scarious. Receptacles flat, paleate; paleae falling, linear, flat or slightly concave-convex, scarious (entire). Ray florets [0, 5] 8 (more in “double” cultivars), neuter; corollas white to pink or purple, or yellow to red-orange. Disc florets 10–20[–80+], bisexual, fertile; corollas yellow [orange] (at least distally), tubes shorter than funnelform throats, lobes 5, ± deltate (staminal filaments hairy near anthers; style branches linear, flattened, thicker distally, hirtellous, appendages relatively slender). Cypselae (dark brown or black) relatively slender, quadrangular-cylindric or -fusiform [outer somewhat obcompressed], sometimes slightly arcuate, attenuate-beaked, not winged [winged], faces glabrous or hispid to scabridulous or ± setose, sometimes papillate, usually with 1 groove; pappi persistent [falling], of 2–4[–8] retrorsely [antrorsely] barbed awns, sometimes 0. x = 12.

Distribution

Tropical and subtropical America, especially Mexico, widely introduced elsewhere.

Discussion

Species ca. 26 (4 in the flora).

Key

1 Ray laminae yellow to red-orange Cosmos sulphureus
1 Ray laminae pink, purple, purplish, rose-pink, violet, or white > 2
2 Leaves: ultimate lobes 2–10 mm wide Cosmos caudatus
2 Leaves: ultimate lobes to 1.5 mm wide > 3
3 Ray laminae 15–50 mm Cosmos bipinnatus
3 Ray laminae 5–9 mm Cosmos parviflorus