Coreopsideae Lindley; Petrobiinae Bentham & Hooker f.

Annuals, perennials, subshrubs, or shrubs, 10–400 cm (sometimes rhizomatous or with cormiform bases, stoloniferous in Coreopsis auriculata). Leaves usually cauline (sometimes mostly basal); usually mostly opposite (distal sometimes alternate), rarely whorled; petiolate or sessile; blades (often pinnately or palmately lobed, sometimes compound), or lobes or leaflets, mostly deltate, elliptic, filiform, lanceolate, linear, oblanceolate, or ovate, ultimate margins entire or toothed, faces usually glabrous or glabrate, sometimes hairy (rarely, if ever, gland-dotted). Heads radiate or discoid, borne singly or in ± corymbiform, cymiform, or paniculiform arrays. Calyculi usually of 3–8(–21+) bractlets or bracts (usually ± herbaceous, usually shorter than phyllaries and/or reflexed, sometimes ± foliaceous and surpassing phyllaries). Involucres mostly campanulate, cylindric, turbinate, or hemispheric or broader. Phyllaries persistent, 3–34+ in ± 2 series (usually distinct, notably connate in Thelesperma), usually ± membranous, margins usually ± scarious. Receptacles mostly flat to convex, paleate (paleae often stramineous to white with red-brown to purplish striae, orbiculate to oblong or linear, ± flat to slightly cupped). Ray florets 0 or 1–21+ (more in cultivars), pistillate and fertile, or neuter, or styliferous and sterile; corollas usually yellow to orange (sometimes bicolored: yellow to orange with brown, red-brown, or purple), sometimes cyanic or white. Disc florets 3–150+, usually bisexual, fertile (functionally staminate in Dicranocarpus); corollas usually yellow to orange, sometimes brown, red-brown, or purple, tubes usually shorter than, sometimes equaling funnelform throats (longer than throats in some Thelesperma spp.), lobes (3–)5, ± deltate to lance-ovate; (staminal filaments hairy in Cosmos) anther thecae pale or dark; stigmatic papillae in 2 lines. Cypselae usually either obcompressed to obflattened, usually cuneate, linear, oblong, orbiculate, or ovate (bodies unequally 3–4-angled, margins often winged), or (all or inner) ± equally 4-angled and linear-fusiform, sometimes ± beaked, faces glabrous or hairy (often striate, tuberculate, or papillate); pappi 0, or persistent, of (1–)2–4(–8), usually ± barbellate awns or scales, rarely coroniform or of 1–2, smooth to ciliate or barbed awns or scales.

Genera 20, species 374 (7 genera, 69 species in the flora): mostly subtropical and warm-temperate New World and Old World.

The circumscription of Coreopsidinae followed here (H. Robinson 1981) is a bit narrower than the traditional one. The subtribe is remarkable among Heliantheae for having a relatively high number of species native in subtropical and tropical Old World, especially Africa. Distinctions among some genera (e.g., Bidens, Coreopsis, and Cosmos) are often subtle.

In Coreopsidinae, each involucre is subtended by a calyculus of more or less herbaceous (sometimes leaflike) bractlets or bracts (sometimes surpassing the phyllaries). In keys and descriptions here, shapes, heights, and diameters given for involucres are based on the phyllaries collectively (exclusive of calyculi) at flowering; the involucres are sometimes notably larger in fruit.