1 "Corolla yellow; leaves with terminal petiolule usually distinctly longer than laterals (equal in rare T. aureum)" 2 1 "Corolla red, pink, cream or white; leaves with all petiolules more or less equal" 4 2 "Leaflets equally petiolulate; corolla 6–7 mm long" "Trifolium aureum" 2 "Central leaflet with petiolule distinctly longer than those of lateral leaflets (at least on upper leaves); corolla 3–6 mm long" 3 3 "Inflorescence globose, 30–50-flowered; flowers imbricate; standard limb orbicular, grooved, hooded over keel in pod" "Trifolium campestre" 3 "Inflorescence hemispherical, 3–20-flowered; flowers not imbricate; standard limb ovate, scarcely grooved, not hooded over keel in pod" "Trifolium dubium" 4 "Inflorescence with all flowers fertile" 5 4 "Inflorescence with 1–6 fertile flowers (with petals) and many infertile flowers (without petals)" 26 5 "Calyx tube conspicuously inflated, bladdery in fruit" 6 5 "Calyx tube not inflated and bladdery in fruit" 9 6 "Flowers non-resupinate (standard uppermost); corolla persistent in fruit" 7 6 "Flowers resupinate (standard lowermost); corolla not persistent in fruit" 8 7 "Plant perennial, prostrate or tufted; leaflet margins minutely toothed; inflorescence to 20 mm long; corolla less than 10 mm long" "Trifolium fragiferum" 7 "Plant annual, upright; leaflet margins prominently toothed; inflorescence more than 20 mm long; corolla more than 10 mm long" "Trifolium vesiculosum" 8 "Peduncles usually longer than subtending leaves; inflorescence globose; calyx throat glabrous, teeth spiny, upper teeth conspicuous in pod" "Trifolium resupinatum" 8 "Peduncles shorter than subtending leaves; inflorescence umbellate; calyx throat with a ring of hairs, teeth blunt, upper teeth obscure in pod" "Trifolium tomentosum" 9 "Leaflets of upper leaves lanceolate, linear-oblong or linear, 5–15 times as long as wide" 10 9 "Leaflets of upper leaves not as above, less than 4 times as long as wide" 11 10 "Leaflets of upper leaves lanceolate; inflorescence 30–80 mm long, usually terminal; peduncles shorter than subtending leaves; calyx tube as long as teeth; corolla not or scarcely exceeding calyx" "Trifolium angustifolium" 10 "Leaflets of upper leaves linear to linear-oblong; inflorescence 10–20 mm long, axillary or terminal; peduncles longer than subtending leaves; calyx tube much shorter than teeth; corolla shorter than calyx" "Trifolium arvense" 11 "Inflorescence 1–10-flowered, pedunculate" 12 11 "Inflorescence usually more than 10-flowered, if fewer-flowered, then inflorescence sessile" 13 12 "Leaflets oblanceolate to obovate; calyx teeth not spreading stellately at maturity; pod 2–9-seeded, distinctly exserted from calyx tube" "Trifolium ornithopodioides" 12 "Leaflets obcordate; calyx teeth spreading stellately at maturity, forming large, bristly heads; pod 1-seeded, included in calyx tube" "Trifolium stellatum" 13 "Inflorescence sessile or peduncles shorter than subtending leaves" 14 13 "Peduncles equal to or longer than subtending leaves" 20 14 "Margins of leaflets almost entire" "Trifolium pratense" 14 "Margins of leaflets variously toothed" 15 15 "Plant completely glabrous or with a few hairs on calyx and bases of leaflets" 16 15 "Plant hairy" 18 16 "Pedicels c. 2 mm long; calyx teeth erect in pod; pod exserted from calyx tube, 3–4 mm long" "Trifolium cernuum" 16 "Pedicel to 1.5 mm long; calyx teeth spreading or recurved in pod; pod included in calyx tube, 2–3 mm long" 17 17 "Inflorescences remote, mostly more than 20-flowered, not obscured by the stipules; corolla pink, longer than calyx" "Trifolium glomeratum" 17 "Inflorescences close together, 1–15-flowered, often clustered near base of plant, largely obscured by the broad membranous stipules; corolla white, shorter than calyx" "Trifolium suffocatum" 18 "Inflorescence clasped by 3 broad-ovate to orbicular involucral stipules; calyx tube 20-veined, teeth blunt; corolla more than 10 mm long, purple" "Trifolium hirtum" 18 "Inflorescence not as above; calyx tube 10-veined, teeth spiny; corolla less than 10 mm long, white or pink" 19 19 "Leaflets with lateral veins mostly recurved and thickened towards the margins; calyx tube throat narrowed by an annular thickening in fruit, lower tooth recurved, others spreading or erect in pod; corolla white" "Trifolium scabrum" 19 "Leaflets with lateral veins mostly straight, not thickened near margins; calyx tube throat open, ciliate, teeth all erect in pod; corolla pink" "Trifolium striatum" 20 "Plant moderately hairy; inflorescence elongated, ovate or cylindrical; corolla usually red to purple (rarely cream)" "Trifolium incarnatum" 20 "Plant sparsely hairy or glabrescent, if ever moderately hairy than inflorescence a globose head; corolla pink, cream or white" 21 21 "Plant creeping, rooting freely at nodes" "Trifolium repens" 21 "Plant erect, decumbent or ascending, never rooting at nodes" 22 22 "Flowers sessile or subsessile; pod included in calyx, usually 1-seeded" 23 22 "Flowers pedicellate; pod exserted from calyx tube, 1–4-seeded" 25 23 "Leaflets minutely dentate; corolla of similar length to calyx; calyx 20-veined, glabrous; calyx lobes 3- or 5-veined at base" "Trifolium lappaceum" 23 "Leaflets entire or minutely dentate; corolla significantly longer than calyx (similar in length to calyx in T. leuchantum); calyx 10-veined, sometimes obscured by hairs; calyx lobes 1- or 3-veined at base" 24 24 "Corolla significantly longer than calyx; calyx lobes unequal" "Trifolium squamosum" 24 "Corolla of similar length to calyx; calyx lobes subequal" "Trifolium leucanthum" 25 "Plant perennial; leaflets entire or minutely serrate; inflorescence mostly 10–20-flowered; calyx teeth unequal; pod 2–4-seeded" "Trifolium hybridum" 25 "Plant annual; leaflets dentate; inflorescence mostly more than 20-flowered; calyx teeth almost equal; pod 1–2-seeded" "Trifolium michelianum" 26 "Prostrate or decumbent annuals; fruiting heads deflexed, subterranean; fertile flowers 2–6; sterile flowers with a wiry calyx" "Trifolium subterraneum" 26 "Erect annuals; fruiting head not subterranean; fertile flowers 1 or 2; sterile flowers densely plumose" "Trifolium pilulare"