1 Flowers lavender or blue.

  2 Leaflets 4-6 (-9) cm long, mostly > 12 mm wide; leaflets not oriented in a vertical plane; fertile stems usually 1-1.5 m tall, the leafy branches ascending; racemes 2-4 (-5) dm long, rather sparsely flowered; petioles 5-20 (-40) mm long; legumes 3.5-4 cm long, 1.0-1.5 cm in diameter; [of flood-scoured riverside cobblebars and rock outcrops, also frequently cultivated and sometimes persistent or escaped]

  2 Leaflets 2-4 (-5) cm long, mostly < 10 mm wide (if wider, then < 4 cm long); leaflets variously oriented (see below); fertile stems usually 0.4-1.0 m tall, the leafy branches horizontally spreading; racemes 1-2.5 (-4) dm long, rather densely flowered; petioles 0-4 (-12) mm long; legumes 3-6 cm long, 1.5-2.5 cm in diameter.

    3 Leaflets mostly oriented in a vertical plane (so the plant is almost invisible when viewed from directly above); petioles (0-) 1-4 (-12) mm long; [of diabase and limestone glades, barrens, and woodlands east of the Mississippi River]

    3 Leaflets not oriented vertically; petioles (0-) 1-18 mm long [of prairies, glades, bluff tops, pastures, and roadsides west of the Mississippi River, IA and NE south through MO, KS, and OK to n. and w. AR and n. TX]

1 Flowers yellow, cream-white, or white.

      4 Flowers white or cream-white.

        5 Flowering pedicels 10-18 (-30) mm long, subtended by persistent bracts 10-25 mm long and 7-10 mm wide; flowers cream-white (to pale-yellow).

          6 Petioles of median leaves 4-10 mm long

          6 Petioles of median leaves 2-4 mm long.

             7 Leaves and stems glabrous; leaflets 1.5-2.5× as long as wide

             7 Leaves and stems pubescent; leaflets (1.5-) 2.5-5× as long as wide

        5 Flowering pedicels 3-10 mm long, subtended by caducous bracts 4-7 mm long and 1-2 mm wide; flowers white.

               8 Calyx 7-8 mm long; corolla 20-25 mm long; petioles (of the lower leaves at least) 10-20 mm long.

                 9 Legume usually 15-20 (-30) mm in diameter, thin-walled and brittle; [of NC south through GA to FL, AL, and MS]

                 9 Legume usually 10-12 (-15) mm in diameter, rigid and tough; [of c. TN, c. KY, AL, and MS westward]

      4 Flowers yellow.

                   10 Flowering pedicels 14-18 (-30) mm long, subtended by persistent bracts 10-25 mm long and 7-10 mm wide; flowers pale-yellow (to cream-white).

                     11 Petioles of median leaves 4-10 mm long

                     11 Petioles of median leaves 2-4 mm long.

                       12 Leaves and stems glabrous; leaflets 1.5-2.5× as long as wide

                       12 Leaves and stems pubescent; leaflets (1.5-) 2.5-5× as long as wide

                   10 Flowering pedicels 2-10 mm long, subtended by caducous bracts 2-10 mm long and 1-2 mm wide; flowers bright yellow.

                          13 Leaflets mostly 1-2.5 (-4) cm long, 1-2.5× as long as wide, the petiolules 0-1 mm long; corolla 12-16 mm long; racemes numerous, terminating most of the branches

                          13 Leaflets mostly 4-9 cm long, 1.5-4× as long as wide, the petiolules 2-10 mm long; corolla 20-28 mm long; racemes solitary (-3) or numerous.

                            14 Inflorescences of racemes of (3-) 5-25 (or more) flowers; stipules persistent or caducous.

                              15 Plant persistently cinereous-pubescent; stipules (some of them at least) persistent; plants blackening on drying

                              15 Plant puberulent when young, soon glabrate to glabrous; stipules caducous; [of MS westward]; plants not blackening on drying

                            14 Inflorescence either of solitary axillary flowers or flowers in clusters of 2-4 in axils or in terminal racemes of 2-4 (-10) flowers; stipules caducous.

                                16 Petiolules 2-3 mm long; leaflets 1-2.5× as long as wide; [of LA, AR, TX, and OK]

                                16 Petiolules 4-10 mm long; leaflets 1.7-5× as long as wide; [of SC, GA, FL, and AL].

                                  17 Leaflets 1.7-3.2 (-5)× as long as wide, the larger typically > 2 cm wide; flowers in racemes of (1-) 3-10 flowers; fruits usually ellipsoid, often > 2× as long as wide; [FL Panhandle, s. AL, and c. peninsular FL]

                                  17 Leaflets 3-5× as long as wide, usually < 1.5 cm wide; flowers usually solitary or in clusters of 2-3; fruits broadly ellipsoid or subspheroidal, < 2× as long as wide; [se. SC south through GA Coastal Plain to ne. FL]