1 Leaves primarily whorled in 3's or 4's (to 5’s).

  2 Largest leaves distinctly spatulate, much wider than thick, 8-20 mm wide; flowers and fruits 4-merous; petals white; [native, of moist forest and rock outcrops]; [section Ternata]

  2 Largest leaves linear-lanceolate, oblanceolate, or elliptic, almost as thick as wide, < 7 mm wide; flowers and fruits 5-merous; petals yellow; [exotic].

    3 Leaves 4 (-5) per whorl; flowering shoots erect

    3 Leaves 3 (-4) per whorl; flowering shoots pendulous, creeping, or ascending.

      4 Flowering shoots pendulous or ascending; leaves linear-lanceolate

      4 Flowering shoots creeping or ascending; leaves oblanceolate to elliptic

1 Leaves primarily alternate.

        5 Flowers and fruits 5-merous.

          6 Leaves 2-5 mm long; petals yellow.

             7 Plant perennial, mat-forming by trailing stems; leaves yellow-green; petals 5-9 mm long, with acute to acuminate apices; [exotic, usually in urban or suburban areas]

             7 Plant annual, stems solitary; leaves pal- or bluish green; petals 2-4 mm long, with mucronate apices; [native, of shallow soils over rock]

          6 Leaves 6-15 mm long; petals yellow or white.

               8 Petals yellow; flowers (5-) 7 (-9) merous

        5 Flowers and fruits 4-merous.

                 9 Leaves of flower-bearing stems linear, sagittate-spurred at the base (the spurs clasping the stem); petals pink to white; annual; [section Ternata]

                 9 Leaves of flower-bearing stems narrowly elliptic, oblanceolate, spatulate, cuneate or short-spurred at the base (not clasping); petals white; perennial or annual.

                   10 Plants annual; sepals 0.4-1 mm long; petals 1.4-4.2 mm long; [restricted to shallow soils of granitic flatrocks of the Piedmont, from s. NC south to wc. GA]; [section Tetrorum]

                   10 Plants perennial; sepals 2-9 mm long; petals 4-9 mm long; [of outcrops of various rocks, not as above]; [section Ternata].

                     11 Leaves of flowering stems with width/thickness ratio of > 2.0; seeds averaging 0.8 mm long; leaves pale green or bluish green, sometimes with a glaucous coating; primary rosettes usually 1.0-2.7 cm in diameter; [MD south through VA and WV to sc. and sw. NC]

                     11 Leaves of flowering stems with width/thickness ratio of < 1.7; seeds averaging 0.7 mm long; leaves green or gray-green, but not glaucous; primary rosettes usually ca. 1 cm in diameter; [se. TN south into AL and GA]