1 "Leaflets 3–9 (at least some leaves with > 3 leaflets)" 2 1 "Leaflets 3" 6 2 "Leaflets generally 7–9; inflorescence 3–5 cm wide" "Trifolium macrocephalum" 2 "Leaflets 3–7; inflorescence 1–2.5 cm wide" 3 3 "Plant silvery or gray, soft-hairy or tomentose; calyx lobe hairs ± 1 mm; Trifolium andersonii" 4 3 "Plant green, strigose, puberulent, or hairy; calyx lobe hairs < 1 mm" 5 4 "Longer petiole hairs 1.5–2 mm; peduncles generally << petioles, inflorescence not or ± exceeding leaves" "Trifolium andersonii subsp. andersonii" 4 "Longer petiole hairs 0.4–1.2 mm; peduncles generally > petioles; inflorescence much exceeding leaves" "Trifolium andersonii subsp. beatleyae" 5 "Leaflet generally elliptic, serrate, teeth 0.1–0.3 mm; inflorescence generally included, 1–1.5 cm wide" "Trifolium gymnocarpon subsp. plummerae" 5 "Leaflet obovate, coarsely serrate, larger teeth 0.4–0.5 mm; inflorescence generally exserted, 1.5–2.5 cm wide" "Trifolium lemmonii" 6 "Flowers of inflorescence, except for outer 2–8, sterile, with calyx stalk-like, without petals, forming bur, delivered to ground by growing peduncle; plant prostrate or creeping" "Trifolium subterraneum" 6 "Flowers of inflorescence fertile, with calyx not stalk-like, with petals, not forming bur, not delivered to ground by peduncle; plant prostrate or creeping or not" 7 7 "Calyx inflated in fruit; inflorescence in fruit spheric or star-shaped, red, brown, green, or white, ± woolly, 0.8–2.5 cm" 8 7 "Calyx rarely inflated in fruit (if inflated then << 2 cm wide); inflorescence in fruit not as at 7." 10 8 "Perennial herb, creeping and rooting or cespitose; bracts of lower flowers forming involucre, ± 2 mm, green; corolla not becoming reflexed" "Trifolium fragiferum" 8 "Annual, decumbent to ± erect, not rooting; bracts of lower flowers generally not forming involucre, < 1 mm, white; corolla becoming reflexed" 9 9 "Inflorescence star-shaped, 1–2.5 cm; flower bracts reduced" "Trifolium resupinatum" 9 "Inflorescence spheric, 0.6–1.2 cm; flower bracts cup-shaped" "Trifolium tomentosum" 10 "Leaf pinnately compound; corolla bright yellow" 11 10 "Leaf palmately compound; corolla not bright yellow (except Trifolium aureum)" 12 11 "Corolla striate; inflorescence 0.8–1.3 cm wide, generally > 20-flowered; petioles of mid-leaves > leaflets" "Trifolium campestre" 11 "Corolla weak-striate; inflorescence 0.4–0.8 cm wide, 5–10(20)-flowered; petioles of mid-leaves generally << leaflets" "Trifolium dubium" 12 "Leaflets 4–10 cm, stipules 1–2.5 cm, green; calyx glabrous; corolla green-white to pink" "Trifolium howellii" 12 "Leaflets or stipules (or both) << above, stipules generally not green; calyx hairy or glabrous; corolla green-white to pink or not" 13 13 "Flowers generally 1–5 per inflorescence, bracts generally inconspicuous; corolla white to lavender-striate; plant generally small; Trifolium monanthum" 14 13 "Flowers > 5 per inflorescence unless plant stressed; corolla white to lavender-striate or not; plant small or not" 17 14 "Rhizomes thin, white; plant mat-forming, not from central crown or thickened taproot; plant glabrous to ± hairy" 15 14 "Rhizomes 0; plant not mat-forming, from central crown or thickened taproot; plant densely hairy" 16 15 "Flowers 1–5, peduncle bent upward at tip; leaflet tips generally acute; SnGb, SnBr, SnJt" "Trifolium monanthum subsp. grantianum" 15 "Flowers 1–4, peduncle straight; leaflet tips generally rounded or truncate; CaR, SN, SNE" "Trifolium monanthum subsp. monanthum" 16 "Leaflet tips generally rounded, truncate, or notched" "Trifolium monanthum subsp. parvum" 16 "Leaflet tips acute to acuminate" "Trifolium monanthum subsp. tenerum" 17 "Pedicels 1–6 mm, flowers generally becoming reflexed" 18 17 "Pedicels < 2 mm, flowers becoming reflexed or not" 31 18 "Corolla bright yellow, 5–7 mm; calyx 1.5–2 mm; stalk-like fruit base 2–3 mm" "Trifolium aureum" 18 "Corolla not bright yellow, generally > 6 mm; calyx generally > 2 mm; stalk-like fruit base 0 or < 2 mm" 19 19 "Leaflet lanceolate; leaves mostly basal, occasionally 2–3 cauline; plants of s SNH, SNE" "Trifolium kingii subsp. dedeckerae" 19 "Leaflet wider than lanceolate, if lanceolate then leaves not mostly basal or plants not of s SNH, SNE" 20 20 "Stem creeping, rooting, turf-forming; petioles from ground level, ± equal; corolla white" "Trifolium repens" 20 "Plant not creeping, not rooting, not turf-forming; petioles not or some from ground level, lower > upper; corolla white or not" 21 21 "Calyx tube puberulent or hairy, occasionally ± so" 22 21 "Calyx tube glabrous" 25 22 "Corolla 5–8 mm; pedicel 2–5 mm" "Trifolium breweri" 22 "Corolla 10–18 mm; pedicel 1–2 mm" 23 23 "Longer petals tapered to beak; 1400–2700 m – MP" "Trifolium longipes subsp. multipedunculatum" 23 "Longer petals acute to acuminate but not beaked; 1200–2700 m" 24 24 "Stems generally well developed, not cespitose; petals generally white, short-tapered, acute, or obtuse; 1200–1800 m; KR, NCoR" "Trifolium longipes subsp. oreganum" 24 "Stems often poorly developed, generally cespitose; petals lavender to purple, longer ones acute to acuminate; 1400–2700 m; KR, CaR" "Trifolium longipes subsp. shastense" 25 "Calyx lobes ciliate with short, flat bristles (or, through breakage, bristle bases); bracts inconspicuous, often in a ring at base of inflorescence" "Trifolium ciliolatum" 25 "Calyx lobes not ciliate; bracts subtending individual flowers or 0" 26 26 "Leaves basal except 1 pair cauline; corolla 10–17 mm" "Trifolium beckwithii" 26 "Leaves cauline; corolla 5–11 mm" 27 27 "Inflorescence 1.5–3 cm wide; bracts conspicuous but soon falling; calyx lobes sharply tapered but not bristle-tipped" "Trifolium hybridum" 27 "Inflorescence 0.5–1.5 cm wide; bracts 0; calyx lobes bristle-tipped" 28 28 "Calyx lobes ± 0.5 mm wide at base, glabrous, tube 1.5–2.5 mm" 29 28 "Calyx lobes ± 0.2 mm wide at base, with generally few hairs, tube 0.8–1.4 mm" 30 29 "Leaflet obovate to obcordate, length 1.5–2.5 × width; CA-FP, DMoj" "Trifolium gracilentum" 29 "Leaflets narrowly elliptic or lanceolate, length 3.5–5 × width; ChI" "Trifolium palmeri" 30 "Leaflet 2.5–5.5 × longer than wide, notched at tip 0.1–0.4 × length, otherwise generally entire" "Trifolium bifidum var. bifidum" 30 "Leaflet 1.5–2.5 × longer than wide, truncate or notched at tip < 0.2 × length, otherwise dentate or entire" "Trifolium bifidum var. decipiens" 31 "Inflorescence sessile at end of stem or in leaf axils, or in leaf axils on short peduncles 6–10 mm, << leaves; corolla 4–6 mm" 32 31 "Inflorescence peduncled (or immediately above 1–2 reduced leaves), peduncle generally > 10 mm, generally > leaves; corolla generally > 5 mm" 34 32 "Inflorescence axillary or at end of stem, peduncles 0" "Trifolium glomeratum" 32 "Inflorescence axillary, peduncles short or short below, 0 above" 33 33 "Corolla > calyx lobes; banner tip notched; peduncles short" "Trifolium cernuum" 33 "Corolla < calyx lobes; banner tip occasionally ± toothed but not notched; peduncles short below, 0 above" "Trifolium retusum" 34 "Banner inflated in fruit; involucre vestigial, ring-like; corolla generally 6–9 mm" "Trifolium depauperatum var. depauperatum" 34 "Banner not inflated in fruit; involucre 0; corolla 6–9 mm or not" 35 35 "Flowers generally reflexed soon after opening; inflorescence often turned to side or downward" 36 35 "Flowers generally not reflexed after opening; inflorescence generally ± erect" 39 36 "Calyx hairy, lobes twisted or bent, plumose" "Trifolium eriocephalum subsp. eriocephalum" 36 "Calyx glabrous, lobes not twisted or bent, not plumose" 37 37 "Inflorescence 1–2 cm wide; calyx 3.5–4.5 mm, generally dark or purple-black; corolla 10–12 mm" "Trifolium bolanderi" 37 "Inflorescence 1.5–3 cm wide; calyx 3–7 mm, not dark or purple-black; corolla 10–17 mm" 38 38 "Calyx 4.5–7 mm; inflorescence erect, axis not exserted" "Trifolium beckwithii" 38 "Calyx 3–4 mm; inflorescence generally turned to side or downward, axis exserted, generally forked" "Trifolium productum" 39 "Inflorescence ± sessile above a pair of reduced leaves, stipules, or both (in Trifolium macraei, occasionally 1 of a pair of inflorescences short-peduncled)" 40 39 "Inflorescence peduncled" 45 40 "Inflorescence generally paired, ± sessile or occasionally 1 short-peduncled above (1)2 leaves" "Trifolium macraei" 40 "Inflorescence single above subtending leaves" 41 41 "Corolla 2-colored (purple with white tips); locally uncommon, s NCoR, n CCo, SnFrB" "Trifolium amoenum" 41 "Corolla not 2-colored (red-purple or pink); sporadic or locally common, CA-FP, GB" 42 42 "Calyx lobes densely to sparsely plumose, lower one ± 1–1.5 × others; corolla pink" 43 42 "Calyx lobes sparsely plumose, straight, lower one ± 2 × others, or calyx lobes glabrous, curved, ± equal; corolla red-purple or pink" 44 43 "Inflorescence spheric, ± 1.5–2 cm; calyx lobes >> tube, densely plumose, 4–6 mm" "Trifolium hirtum" 43 "Inflorescence ± short-cylindric, 0.5–1.5 cm; calyx lobes <= tube except lower one, sparsely plumose, 1–2.5 mm" "Trifolium striatum" 44 "Leaflets elliptic to obovate, ± entire; calyx hairy, veins 10, lobes straight; corolla generally red-purple" "Trifolium pratense" 44 "Leaflets generally lanceolate to elliptic, teeth bristle-like; calyx glabrous, veins 24, lobes straight to curved; corolla pink to purple" "Trifolium vesiculosum" 45 "Corolla <= calyx; calyx lobes > tube, plumose" 46 45 "Corolla > calyx; calyx lobes > tube or not, plumose or not" 49 46 "Leaflets oblanceolate to obovate, length 1.2–3 × width; corolla 2-colored (purple with white tips)" 47 46 "Leaflets linear to narrow-lanceolate, -oblong, or -oblanceolate, length 3–8 × width; corolla 1-colored (pale pink to white)" 48 47 "Calyx 4–8 mm, lobes 3–6.5 mm" "Trifolium albopurpureum" 47 "Calyx 8–14 mm, lobes 6.5–12 mm" "Trifolium columbinum" 48 "Corolla 10–12 mm, ± = calyx" "Trifolium angustifolium" 48 "Corolla 3–4 mm, < or << calyx" "Trifolium arvense" 49 "Perennial herb; calyx lobes glabrous or hairs few, curved or wavy" 50 49 "Annual; calyx lobes ± plumose, hairs generally straight" 56 50 "Inflorescence < 1 cm wide, flowers generally 1–5, erect; Trifolium monanthum" 51 50 "Inflorescence 1.5–3 cm wide, flowers > 5, ascending-spreading" 54 51 "Rhizomes thin, white; plant mat-forming, not from central crown or thickened taproot; plant glabrous to ± hairy" 52 51 "Rhizomes 0; plant not mat-forming, from central crown or thickened taproot; plant densely hairy" 53 52 "Flowers 1–5, peduncle bent upward at tip; leaflet tips generally acute; SnGb, SnBr, SnJt" "Trifolium monanthum subsp. grantianum" 52 "Flowers 1–4, peduncle straight; leaflet tips generally rounded or truncate; CaR, SN, SNE" "Trifolium monanthum subsp. monanthum" 53 "Leaflet tips generally rounded, truncate, or notched" "Trifolium monanthum subsp. parvum" 53 "Leaflet tips acute to acuminate" "Trifolium monanthum subsp. tenerum" 54 "Calyx lobes 3–5 × tube; leaflet length generally 6–10 × width; KR, NCoR, CaR" "Trifolium longipes subsp. elmeri" 54 "Calyx lobes 1–3 × tube; leaflet length 2–6 × width in CA-FP, to 10 × in GB; KR, NCoR, CaR, SN, SnBr, SnJt, GB" 55 55 "Roots thickened, fusiform; rhizomes ± 0; calyx lobes densely long-hairy" "Trifolium longipes subsp. atrorubens" 55 "Roots generally not thickened, not fusiform; rhizomes present; calyx ± glabrous" "Trifolium longipes subsp. hansenii" 56 "Corolla 2-colored (purple with white tips)" 57 56 "Corolla 1-colored (purple, crimson, pink, white, or cream)" 58 57 "Corolla 12–16 mm; calyx 10–12 mm" "Trifolium amoenum" 57 "Corolla 7–12 mm; calyx 4–8 mm" "Trifolium dichotomum" 58 "Corolla cream; inflorescence ovate to spheric, 1–2.5 cm; leaflets elliptic to oblanceolate; stipules long-tapered" "Trifolium alexandrinum" 58 "Corolla crimson or white; inflorescence ± cylindric or ± conic, 2–6 cm; leaflets obovate to obcordate; stipules widely rounded" "Trifolium incarnatum"