1 "Calyx or banner soon inflated in fruit; involucre bracts generally ± free" 2 1 "Calyx, corolla not inflated in fruit (except lower part of banner in Trifolium barbigerum); involucre bracts generally fused into a cup-, bowl-, or wheel-shaped, toothed or cut ring (except generally ± free in Trifolium monanthum)" 6 2 "Calyx hairy, inflated in fruit; inflorescence in fruit ± 2 cm wide, spheric, fuzzy; banner not inflating in fruit; perennial herb, stoloned" "Trifolium fragiferum" 2 "Calyx glabrous, not inflated in fruit; inflorescence not as above; banner inflating in fruit; annual, not stoloned" 3 3 "Corolla 10–20 mm" "Trifolium fucatum" 3 "Corolla 4–9 mm" 4 4 "Involucre bracts < 1 mm, fused at base; inflorescence generally 1–1.5 cm wide; corolla 6.5–9 mm; ScV, nw SnJV, CW" "Trifolium hydrophilum" 4 "Involucre bracts 2–2.5 mm, ± free to ± 1/2 fused; inflorescence 0.5–1 cm wide; corolla 4.5–7.5 mm; NCoR, CaRF, SNF, Teh, GV, CW, SCo, ChI, PR; Trifolium depauperatum" 5 5 "Fruit 3–4 mm, oblong, stalk-like base 0 or short; involucre bracts ± free or ± 1/2 fused, margins widely scarious, toothed near tip; corolla 5–6 mm; GV, SnFrB, SCoR" "Trifolium depauperatum var. amplectens" 5 "Fruit 2–3 mm, ovate or obovate, stalk-like base 0.5–1 mm; involucre bracts ± free, margins ± membranous; corolla 4.5–7.5 mm; NCoR, CaRF, SNF, Teh, GV, CW, SCo, ChI, PR" "Trifolium depauperatum var. truncatum" 6 "Involucre cup- or bowl-shaped, when pressed generally partly hiding flowers (except in Trifolium grayi)" 7 6 "Involucre wheel-shaped or bracts ± free, when pressed hiding only bases of flowers" 13 7 "Calyx lobes < 1/2 tube, not bristle-tipped" "Trifolium microdon" 7 "Calyx lobes > 1/2 tube, bristle-tipped" 8 8 "Calyx lobes, involucre lobes ± entire; plant hairs generally finely wavy" "Trifolium microcephalum" 8 "Calyx lobes, involucre lobes, or both toothed, cut, or branched; plant hairs 0 or finely wavy or not" 9 9 "Bristle-tips of lower 3 calyx lobes generally forked; involucre margin wavy, finely toothed" "Trifolium cyathiferum" 9 "Bristle-tips of lower 3 calyx lobes not divided; involucre margin wavy or not, generally coarsely toothed or cut 1/2 to involucre base" 10 10 "Calyx lobes finely toothed, bristle at tip 1–1.5 mm, glabrous; involucre generally glabrous; banner not inflated" "Trifolium buckwestiorum" 10 "Calyx lobes entire, bristle at tip 3–4 mm, plumose (or lower lobes divided to near base into 2–3 bristles, each 3–4 mm, generally plumose); involucre generally puberulent; banner inflated below, persistent as twisted beak above" 11 11 "Corolla gold- to sulphur-yellow; leaves, stems glabrous; seeds > 3 mm; ScV (North Table Mtn Plateau, Butte Co.)" "Trifolium jokerstii" 11 "Corolla purple, pink-purple, white, or 2-colored; leaves, stems generally hairy; seeds < 3 mm; NW, SN, GV, CW" 12 12 "Corolla 5–10 mm, <= (rarely ± >) calyx; stalk-like fruit base < 1 mm; inflorescence generally bristly from calyx lobes" "Trifolium barbigerum" 12 "Corolla 8–16 mm, > calyx; stalk-like fruit base 1–3 mm; inflorescence not bristly" "Trifolium grayi" 13 "Involucre vestigial or bracts 2–5, inconspicuous, generally ± free, 1–3 mm; inflorescence 1–6-flowered; Trifolium monanthum" 14 13 "Involucre generally conspicuous, bracts indefinite in number, generally > 5 mm, fused, if inconspicuous (e.g., 2–3 mm in Trifolium oliganthum) fused at least at base; inflorescence generally 8–many-flowered" 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 "Perennial herb; involucre generally 2–3 cm wide; seeds 2–4" 18 17 "Annual; involucre < 2 cm wide; seeds generally 1–2" 19 18 "Thickened fusiform root present; rhizomes 0; KR" "Trifolium siskiyouense" 18 "Thickened fusiform root 0; rhizomes present; NW, CaR, SN, SnJV, CW, SCo, PR, SNE" "Trifolium wormskioldii" 19 "Calyx lobes ± <= tube, often toothed or shouldered below tapered tip; calyx tube splitting between upper lobes" 20 19 "Calyx lobes generally > tube, generally entire (occasionally ± forked in Trifolium trichocalyx), not shouldered below tapered tip; calyx tube not splitting between upper lobes" 22 20 "Flower 5–8 mm; involucre 2–3 mm, generally cut > 1/2 to base; inflorescence 6–10 mm wide, 5–15-flowered" "Trifolium oliganthum" 20 "Flower 9–18 mm; involucre > 3 mm, cut < 1/2 to base; inflorescence generally 12–30 mm wide, often > 15-flowered" 21 21 "Calyx glandular-hairy or bumpy (occasionally in age glabrous), lobes generally entire; leaflets sharply serrate, longer teeth ± 1 mm" "Trifolium obtusiflorum" 21 "Calyx glabrous, not bumpy, lobes entire or 3-toothed; leaflets serrate, teeth < 1 mm" "Trifolium willdenovii" 22 "Calyx hairy; involucre small, cut past middle – CCo (Monterey Peninsula)" "Trifolium trichocalyx" 22 "Calyx generally ± glabrous; involucre generally well developed, cut to middle" 23 23 "Calyx tubular, lobes ± 3-parted – CCo (Monterey Peninsula)" "Trifolium polyodon" 23 "Calyx bell-shaped, lobes entire or toothed; Trifolium variegatum" 24 24 "Inflorescence 1–5-flowered; corolla 3.5–9 mm" "Trifolium variegatum var. geminiflorum" 24 "Inflorescence 5–many-flowered; corolla 6–16 mm" 25 25 "Inflorescence 1.5–3 cm, 10–many-flowered, corolla 9–17 mm" "Trifolium variegatum var. major" 25 "Inflorescence 1–1.5 cm, 5–10-flowered, corolla 6–10 mm" "Trifolium variegatum var. variegatum"