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Key to Lotus

Fabaceae

Lotus

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1 Leaves 3-foliolate, the upper commonly 1-foliolate; flowers solitary in leaf axils
1 Leaves 5-foliolate; flowers in umbels.
  2 Inflorescences (4-) 5-15-flowered; stems hollow; perennials from rhizomes
  2 Inflorescences (1-) 3-8 (-10) flowered; stems solid; annuals or perennials from taproots (rarely rhizomatous).
    3 Calyx tube 2.8-3.5 mm long; corolla 10-17 mm long; leaflets of the medial leaves mostly 1.5-2.5 (-5)× as long as wide
    3 Calyx tube 1.8-2.8 mm long; corolla 7-10 mm long; leaflets of the medial leaves 3-4 (-6)× as long as wide

Key to Fabaceae, Key I: herbaceous legumes with all leaves unifoliolate or leaflets absent [subfamily Faboideae]

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1 Tendrils present on plant; leaves modified into tendrils (leaflike structures present clearly interpretable as stipules); [tribe Fabeae].
  2 Legume 4-7 mm wide; corolla 10-13 mm long
  2 Legume 12-20 mm wide; corolla 18-25 mm long
1 Tendrils absent; leaves or stipules present on plant and interpretable as leaves with 1 leaflet.
    3 Leaflet blades roundish, 0.6-1.5× as long as wide.
      4 Leaves with a well-developed petiole, > 0.5 cm long.
        5 Leaflet margins dentate; corollas white to pink; [tribe Psoraleeae]
        5 Leaflet margins entire; corollas yellow; [tribe Phaseoleae]
      4 Leaves sessile, subsessile, or perfoliate.
          6 Corolla bright or creamy yellow; stamens separate; leaves all 1-foliolate; leaflet blades perfoliate or sessile; [tribe Thermopsideae]
          6 Corolla violet to blue (drying pale); stamens diadelphous; leaves 1-foliolate and with some leaves 3-foliolate or 2-foliolate; leaflet blades cuneate, subsessile; [tribe Psoraleeae]
    3 Leaflet blades elongate, 1.5-15× as long as wide.
             7 Leaves basally disposed.
               8 Leaflet blades elliptic, widest near the midpoint of the blade; flowers pink, rose, or purplish; legume straight; [native of the Coastal Plain, se. NC south to s. FL, west to e. LA]; [tribe Genisteae]
               8 Leaflet blades oblanceolate, widest well past the midpoint of the blade; flowers yellow; legume coiled; [rare waif]; [tribe Loteae]
             7 Leaves all or primarily cauline.
                 9 Leaves long-petioled, the petiole > 2 cm long.
                   10 Petiole winged its entire length; leaflet blade 2-4× as long as wide, sagittate at the base; foliage not glandular; [tribe Phaseoleae]
                   10 Petiole not winged; leaflet blade 8-15× as long as wide, cuneate at the base; foliage glandular-punctate; [tribe Psoraleeae]
                 9 Leaves sessile, subsessile, or short-petiolate, the petiole < 1.5 cm long.
                     11 Stamens monadelphous; corolla yellow, 8-30 mm long; [tribe Crotalarieae]
                     11 Stamens diadelphous; corolla purple, lavender, or cream, 5-15 mm long.
                       12 Corolla 11-15 mm long, purple; [se. and s. TX]; [tribe Diocleae]
                       12 Corolla 5-7 mm long, lavender or cream; [widespread in our area]
                          13 Flowers solitary in leaf axils; [tribe Loteae]
                          13 Flowers in racemose inflorescences; [tribe Desmodieae]

Key to Fabaceae, Key K: herbaceous legumes with pinnately trifoliolate leaves [subfamily Faboideae]

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1 Leaflets denticulate (sometimes inconspicuously so); [tribe Trifolieae].
  2 Inflorescences elongate racemes with an axis 5-15 cm long, the flowers well-spaced along the axis, the overall inflorescence much longer than its diameter
  2 Inflorescences umbellate or headlike clusters or short racemes with an axis < 2 cm long, the flowers closely clustered, the overall inflorescence little (if at all) longer than its diameter.
    3 Legumes spirally coiled or curved, often tuberculate or prickly; stems 4-angled towards the tip; leaves pinnately trifoliolate; calyx actinomorphic
    3 Legumes straight or nearly so, never tuberculate or prickly; stems terete or flattened (2-angled) towards the tip; leaves palmately 3-foliolate; calyx zygomorphic
1 Leaflets entire (and sometimes also with 1 or 2 broad lobes), or with scattered, irregular large teeth (Pachyrhizus erosus).
      4 Main stems erect or ascending, not trailing, twining, or otherwise vine-like.
        5 Flowers not papilionaceous (the wings and keel epistemonous, arising terminally or laterally from the stamen tube), barely bilaterally symmetrical; stamens 5, monadelphous; [tribe Amorpheae]
        5 Flowers papilionaceous; stamens 10, diadelphous or monadelphous.
          6 Plants with separate leafy and flowering stems (the flowering stems naked or nearly so of leaves).
             7 Standard bright red, remaining folded, 30-50 mm long; leaves hastately lobed; fruit a torulose legume, 6-20 cm long, the seeds red; [tribe Phaseoleae]
             7 Standard white or pink, expanded, 4-8 mm long; leaves not hastate; fruit a flattened loment, < 5 cm long, the seeds drab; [tribe Desmodieae]
          6 Plants bearing leaves and flowers on the same stems.
               8 Leaves, stems, and/or calyces glandular-punctate.
                 9 Corollas pink or lavender/purplish; leaflets estipellate; fruit 1-seeded, indehiscent; [tribe Psoraleae]
                 9 Corollas yellow; leaflets stipellate; fruit 2-many-seeded, dehiscent; [tribe Phaseoleae, subtribe Cajaninae]
               8 Leaves, stems, and calyces lacking punctate glands.
                   10 Leaflet blades large, at least the largest terminal leaflets on a plant > 5 cm long.
                     11 Stipels absent on the petiolules of mature leaflets; stamens monadelphous.
                       12 Fruit a legume (not segmented into 1-seed dispersal units), hairy but the hairs not hooked; [plants cultivated as garden plants, rare as waifs]
                       12 Fruit a loment (separating into single-seeded segments), uncinulate (with hooked hairs, the fruits attaching to hairs or clothes as 'stick-tights'); [plants widespread, common]
                     11 Stipels present, persistent; stamens diadelphous (9 and 1).
                          13 Fruit a loment (separating into single-seeded segments), uncinulate (with hooked hairs, the fruits attaching to hairs or clothes as 'stick-tights'); [plants widespread, common]
                          13 Fruit a legume (not segmented into 1-seed dispersal units), hairy but the hairs not hooked; [plants cultivated as crops or garden plants, rare as waifs]
                            14 sKeel of corolla not coiled; stipules inconspicuous; [soy beans]
                            14 Keel of corolla coiled 1-3 turns; stipules conspicuous, persistent, striate; [bush green beans or lima beans]
                   10 Leaflet blades smaller, all on a plant < 5 cm long.
                              15 Stipels present, persistent.
                                16 Fruit a loment (separating into single-seeded segments), uncinulate (with hooked hairs, the fruits attaching to hairs or clothes as 'stick-tights')
                                16 Fruit a several- to many-seeded legume, glabrous to hairy (but not uncinulate)
                              15 Stipels absent on the petiolules of mature leaflets.
                                  17 Fruits dehiscent, a legume with 2 or more seeds.
                                    18 Terminal leaflet 2× or more as long as the 2 lateral leaflets; banner petal evenly colored
                                  17 Fruits indehiscent: either 1-seeded, or a loment with 2 or more one-seeded (indehiscent) segments.
                                       19 Petioles fused most of length with amplexicaul stipules, the leaves thus appearing sessile or nearly so; corollas lemon to orangy yellow; flowers subsessile; fruit a loment of 2 segments, the terminal segment fertile, the lower segment either sterile or fertile
                                       19 Petioles free from stipules, leaves evidently petiolate; corollas white to pink; flowers pedicellate; fruit either 1-seeded, or a loment normally with 3+ segments
                                         20 Fruit a loment, with 1-3 segments; terminal leaflets 3-10 cm long, 1-1.5× as long as wide; stamens monadelphous
                                         20 Fruit 1-seeded; terminal leaflets 1-5 cm long, 1.2-8× as long as wide; stamens diadelphous (9 and 1)
      4 Main stems trailing, twining, creeping, or climbing or sprawling over other vegetation.
                                           21 Leaves, stems, and/or calyces glandular-punctate; corollas yellow.
                                           21 Leaves, stems, and calyces lacking punctate glands; corollas yellow, pink, purplish, white, red, blue.
                                             22 Leaflet blades smaller, all on a plant < 5 cm long.
                                               23 Stipels absent on the petiolules of mature leaflets.
                                                 24 Fruit a loment of 2 segments, the terminal segment fertile, the lower segment either sterile or fertile; corollas lemon to orangy yellow
                                                 24 Fruit 1-seeded; corollas pink-purplish to white, or bronze to brick-red.
                                                    25 Corollas pink-purplish to white
                                                    25 Corollas bronze to brick-red
                                               23 Stipels present, persistent (minute in Amphicarpaea).
                                                      26 Fruit a loment (separating into single-seeded segments), uncinulate (with hooked hairs, the fruits attaching to hairs or clothes as 'stick-tights').
                                                        27 Flowers in axillary or terminal racemes; leaflets rotund, broadly ovate, broadly elliptic, or narrowly elliptic, the larger > 1 cm long.
                                                        27 Flowers in axillary clusters; leaflets broadly obovate, 0.5-1 cm long
                                                      26 Fruit a legume, dehiscent (at least tardily), unsegmented, and with 2+ seeds.
                                                          28 Flowers resupinate (the pedicel twisted 180 degrees), the banner 2.5-5.5 cm long and positioned lowermost.
                                                            29 Calyx lobes equal to or longer than the calyx tube; fruits 3-5 mm wide
                                                            29 Calyx lobes shorter than the calyx tube; fruits 5-8 mm wide
                                                          28 Flowers not resupinate, the banner 0.7-2.5 cm long and positioned uppermost.
                                                              30 Stipules caducous
                                                              30 Stipules persistent, sometimes conspicuous, sometimes striate.
                                                                 31 Keel petal and the included style straight to gently upcurved; stems very slender, < 0.75 mm in diameter
                                                                 31 Keel petal and the included style either strongly curved upwards 90-180 degrees, or even more extensively coiled (asymmetrically and spirally) in towards the flower center; stems slender to thicker, > 0.75 mm in diameter.
                                                                   32 Keel petal and the included style strongly curved upwards 90-180 degrees; corollas yellow or pink to lavender (or whitish).
                                                                     33 Corollas pink to lavender (or whitish); corolla keel usually somewhat twisted, asymmetrical; [widespread in our region]
                                                                     33 Corollas yellow (except pink in V. unguiculata); corolla keel symmetrical; [mainly outer Coastal Plain, introduced inland]
                                                                   32 Keel petal and the included style extensively coiled > 180 degrees (asymmetrically and spirally) in towards the flower center; corollas pink, purple, maroon, purple-black (or whitish).
                                                                       34 Peduncles long, the flowers borne in clusters on a raceme axis shorter than the peduncle; plants glabrate to villous, the hairs not hooked
                                                                       34 Peduncles short, the flowers scattered along a (sometimes branched) raceme axis, the raceme axis about as long as or longer than the peduncle; plants uncinulate pubescent (use 20× magnification, or touch the plant for the 'tacky' feel)
                                             22 Leaflet blades large, at least the largest terminal leaflets on a plant > 5 cm long.
                                                                         35 Stipels absent on the petiolules of mature leaflets; stamens monadelphous
                                                                         35 Stipels present, persistent (minute in Amphicarpaea); stamens diadelphous (9 and 1) or monadelphous (Pueraria).
                                                                           36 Stamens monadelphous; robust herbaceous vine with stems to 30 m long; flowers purple, when fresh smelling like artificial grape flavoring.
                                                                           36 Stamens diadelphous (9 and 1); herbaceous vines with stems usually < 5 m long; flowers various in color, not 'grapy' in odor.
                                                                              37 Flowers resupinate (the pedicel twisted 180 degrees), the banner (standard) petal lowermost; banner (standard) 25-50 mm long, much larger than the other petals.
                                                                                38 Calyx lobes equal to or longer than the calyx tube; fruits 3-5 mm wide
                                                                                38 Calyx lobes shorter than the calyx tube; fruits 5-8 mm wide
                                                                              37 Flowers not resupinate, the banner (standard) uppermost; banner (standard) < 25 mm long, or if up to 30 mm then not much longer than the other petals.
                                                                                  39 Fruit a loment (separating into single-seeded segments), uncinulate (with hooked hairs, the fruits attaching to hairs or clothes as 'stick-tights')
                                                                                  39 Fruit a several- to many-seeded legume, glabrous to hairy (but not uncinulate).
                                                                                    40 Keel incurved < 90 (-120) degrees; style glabrous or pubescent.
                                                                                      41 Stipules inconspicuous or obsolescent.
                                                                                        42 Leaflets coarsely toothed; roots tuberous
                                                                                        42 Leaflets with entire margins (sometimes with 1-2 rounded lobes); roots slender
                                                                                           43 Corolla 3-4 cm long; fruits constricted between the seeds; fruits with stinging hairs
                                                                                           43 Corolla < 2 cm long; fruits constricted or not; fruits glabrous or hairy, the hairs not stinging.
                                                                                             44 Bracteoles below the calyx persistent; ventral suture of the fruit bumpy-nodose; style bearded
                                                                                             44 Bracteoles caducous; ventral suture of the fruit not bumpy-nodose; style glabrous.
                                                                                               45 Leaflets (2-) 4-8 cm long, 0.8-1.5 cm wide, 5-6× as long as wide; leaflet apices acute to obtuse; fruits not flanged or winged
                                                                                               45 Leaflets 6-14 cm long, 4-10 cm wide, 1-1.3× as long as wide; leaflet apices strongly acuminate; fruits with a flange or wing along the ventral suture
                                                                                      41 Stipules persistent and conspicuous.
                                                                                                 46 Legume quadrangular in ×-section, 4-winged
                                                                                                 46 Legume circular, elliptic, or oblong in ×-section, not winged.
                                                                                                   47 Keel petal and the included style straight to gently upcurved; stems very slender, < 0.75 mm in diameter
                                                                                                   47 Keel petal and the included style strongly curved upwards 90-180 degrees; stems slender to thicker, > 0.75 mm in diameter
                                                                                    40 Keel petal and the included style either strongly curved upwards 90-180 degrees, or even more extensively coiled (asymmetrically and spirally) in towards the flower center; style or stigma pubescent.
                                                                                                     48 Plants uncinulate pubescent (use 20× magnification, or touch the plant for the 'tacky' feel)
                                                                                                     48 Plants glabrate to villous, the hairs not hooked.
                                                                                                        49 Keel petal and the included style strongly curved upwards 90-180 degrees
                                                                                                          50 Corolla keel symmetrical; [mainly outer Coastal Plain]
                                                                                                          50 Corolla keel usually somewhat twisted, asymmetrical; [widespread in our region]
                                                                                                        49 Keel petal and the included style even more extensively coiled (asymmetrically and spirally) in towards the flower center.
                                                                                                            51 Corolla 2.5-4 cm long, the wings about as long as the other petals; leaflets not lobed
                                                                                                            51 Corolla 1.5-2 cm long, the wing petals longer than the other petals; leaflets lobed