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Key to Potentilla

Rosaceae

Potentilla

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1 Leaves pinnately compound, with (5-) 7-21 (-31) leaflets.
  2 Leaves with (5-) 7-21 (-31) leaflets; flowers solitary, on naked, axillary pedicels; lower leaf surface silvery-white, densely appressed-hairy
  2 Leaves with 5-9 leaflets; flowers (10-) 20-100 (or more) in a cyme or raceme; lower leaf surface green, glabrate or sparsely hairy; [section Rivales]
1 Leaves palmately compound, with 3-9 leaflets.
    3 Flowers solitary, on naked, axillary pedicels; leaves either palmately 3-5-foliolate or pinnately (5-) 7-21 (-31)-foliolate.
      4 Leaves 3-foliolate; fruit strawberry-like, fleshy and red, pink, or almost white, consisting of an expanded fleshy receptacle bearing superficial achenes; [formerly genus Duchesnea]
        5 Achenes rugose -tubercled, dull or matte when fresh; receptacle surface white to pink, dull or matte, the neck of the receptacle white or pale pink; flowers 0.5-1.5 cm in diameter; leaflets mostly 1.5-2.5 cm long
        5 Achenes smooth or nearly so, shining when fresh; receptacle surface red, shining when fresh, the neck of the receptacle red or dark pink; flowers 1.5-2.5 cm in diameter; leaflets mostly 2-3.5 cm long
      4 Leaves primarily 5-foliolate on a plant (some poorly developed leaves may be 3-4-foliolate); fruit a head of achenes, dry; [section Potentilla].
          6 Sepals 4; petals 4; stems branching when well-developed; leaves with 3-5 leaflets; [rare waif]
          6 Sepals 5; petals 5; stems not branching; leaves with 5 leaflets (fewer only on smaller or poorly developed leaves); [collectively common and widespread].
             7 Plants lacking rhizomes; petals (6-) 8-12 mm long; anthers 1.3-2.0 mm long
             7 Plants with horizontal rhizomes; petals 4-10 mm long; anthers 0.6-1.0 mm long.
               8 Terminal leaflet (of well-developed leaves) toothed for < ½ its length, with 2-7 teeth per leaflet side; terminal leaflet usually < 2× as long as wide; lowest flower produced from the axil of the 1st stem leaf above the plant base, typically with only 1 leaf and pedicel at each subsequent node; plants often flowering on short stolons obscured by basal leaves; stem usually prostrate from the beginning, 0.3-0.8 mm in diameter
               8 Terminal leaflet (of well-developed leaves) toothed for > ½ its length, with 4-8 (-13) teeth per leaflet side; terminal leaflet usually > 2× as long as wide; lowest flower produced from the axil of the 2nd stem leaf above the plant base, typically with 2 leaves and 1 pedicel at each subsequent node; plants only flowering on elongating stolons; stem usually erect initially, 0.9-1.4 mm in diameter
    3 Flowers in terminal cymes; leaves palmately 3-9-foliolate.
                 9 Leaves 3-foliolate (sometimes with some leaves 5-foliolate); [section Rivales].
                   10 Hairs of the stem stiff, tubercle-based, to 3 mm long; petals (2-) 3-5 mm long; stamens (15-) 20; achenes usually ridged, tan or brown, 0.8-1.3 mm long
                   10 Hairs of the stem weak, not tubercle-based, to 1.5 mm long; petals 1.5-2 mm long; stamens (5-) 10 (-15); achenes smooth, white or yellowish, 0.7-0.9 mm long
                 9 Leaves 5-9-foliolate.
                     11 Leaves (5-) 7-9-foliolate; petals 8-15 mm long, pale (sulfur) yellow; [section Rectae]
                     11 Leaves 5 (-7)-foliolate; petals 3-7 (-8) mm long, medium yellow; [section Terminales].
                       12 Leaves pubescent beneath, the green surface not concealed; petals 4-5 mm long
                       12 Leaves densely tomentose beneath, the surface concealed; petals either 2.5-4 mm long or 5-7 (-8) mm long.
                          13 Pubescence of the stem and veins of the leaf undersurface tomentose only; lower leaf surface silvery-white tomentose; leaves revolute; petals 2.5-4 mm long
                          13 Pubescence of the stem and veins of the leaf undersurface tomentose and also with long, spreading hairs; lower leaf surface somewhat to strongly grayish-tomentose; leaves not revolute; petals 5-7 (-8) mm long