Description: Annual or [perennial] woody herbs.
Leaves opposite, cauline, usually petiolate sometimes sessile, simple or compound.
Heads terminal on long peduncles, in loose cymes or solitary, radiate or the rays absent; heads narrow-ovate or hemispherical, reflexed in fruit, 2-seriate, outer bracts herbaceous, inner bracts with membranous margins; receptacle flat or slightly convex, pitted, with caducous scales. Ray florets few or absent, sterile, ligulate, yellow or white. Disc florets bisexual, fertile, tubular, 5-merous, yellow or greenish. Anthers and style with terminal appendages. Style branches linear.
Achenes linear or oblong-cuneate, laterally compressed or 4-angled, ribbed; pappus of 2–4 stiff, retrorsely barbed awns.
Distribution and occurrence: World: 230 species, tropical & warm-temp. regions. Australia: 5 species (naturalized), Qld, N.S.W., Vic., N.T., S.A.
Text by J. Everett
| ||Key to the species|| |
|1||Outer involucral more or less spathulate, leaf-like, often extending beyond the involucre; achenes retrorsely barbed||Bidens tripartita|
|Outer involucral bracts spathulate, linear or lanceolate, finely hairy on margins, and shorter than inner bracts; achenes antrorsely barbed (but barbs on awns retrorse)||2|
|2||Leaves markedly 3- or 5-lobed, leaflets usually entire and toothed||Bidens pilosa|
|Leaves mostly 5- to 7-lobed, leaflets pinnatifid|
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|3||Pappus awns erect; peduncles and margins of involucral bracts glabrous or with scattered small septate hairs; leaflet lobes usually linear to lanceolate||Bidens subalternans|
|Pappus awns spreading; peduncles and margins of involucral bracts conspicuously ciliate with spreading septate hairs; leaflet lobes rhombic to broad-lanceolate|
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