Flora of the Southeastern United States

1 Leaves mostly 6 per node (ranging from 5-8) at the primary nodes

1 Leaves mostly 8 or more per node at the primary nodes

1 Flowers pink, purple, or blue, in terminal heads, subtended by an involucre of leaves fused at the base; stem rough-hairy or retrorse-scabrid; [exotic].

  2 Leaves obtuse at tip; leaves 6-8 per whorl; stem retrorse-scabrid

  2 Leaves acute to acuminate at tip; leaves (4-) 6 per whorl; stem rough-hairy

1 Flowers white, yellow, or green, in axillary or terminal diffuse inflorescences, not subtended by an involucre; stems either smooth, retrorse-scabrid, or pubescent.

    3 Largest leaves < 10 mm long; fruits 0.7-1 mm across; annual; [exotic].

      4 Inflorescence relatively diffuse, branches divaricate; ultimate fruits (2-) 3-6 (-7) nodes beyond primary stem axis (with largest leaves); first inflorescence internode (beyond primary stem axis) 15-50 mm long; fruit surface glabrous (without hairs)

      4 Inflorescence relatively strict, branches ascending; ultimate fruits 2-3 (-4) nodes beyond primary stem axis (with largest leaves); first inflorescence internode (beyond primary stem axis) 3-12 (-20) mm long; fruit surface glabrous or bristly-hispid.

        5 Fruit surface without hairs, smooth to shallowly papillate

        5 Fruit surface bristly-hispid with uncinate-tipped hairs, distinctly papillate

    3 Largest leaves > 10 mm long; fruits 1-2.5 mm across; perennial; [native].

          6 Fruits and ovaries uncinate-hispid; leaves 15-50 mm long, 7-10 mm wide

          6 Fruits and ovaries glabrous or papillose; leaves 5-25 mm long, 1-6 mm wide.

             7 Corolla 1.5-2.5 mm across, 3-lobed; [collectively widespread in our region].

               8 Fruiting pedicels (4-) 5-8 (-12) mm long; pairs of fruits (3-) 3.5-5 mm across at maturity; leaves 2-3 (-4) mm wide

               8 Fruiting pedicels (2-) 2.5-5 (-6) mm long; pairs of fruits (2-) 2.5-3 mm across at maturity; leaves (1.5-) 2-2.5 (-2.8) mm wide

             7 Corolla 2.5-4.5 mm across, 4-lobed; [mostly of the Mountains in our area, extending into the Piedmont or even the Coastal Plain in n. VA and northward].

                 9 Leaf margins retrorsely ciliate-scabrid; leaves 3-5× as long as wide; [plants of bogs and moist thickets]

                 9 Leaf margins antrorsely ciliate-scabrid; leaves 4-8× as long as wide; [plants of dry forests and woodlands].

                   10 Leaves sharply acute or cuspidate; corolla 2.5-3 mm across

                   10 Leaves rounded, obtuse, or barely acute; corolla ca. 4 mm across

1 Leaves 8-12 per whorl (many whorls with > 8 leaves); flowers bright yellow, in a large showy terminal compound inflorescence; fruits glabrous; perennial.

  2 Flowers golden-yellow, fragrant; inflorescence dense, usually not interrupted

  2 Flowers lemon-yellow, odorless; inflorescence interrupted

1 Leaves (5-) 8 (-10) per whorl (few if any whorls with > 8 leaves); flowers white or greenish, in a terminal compound inflorescence or in small axillary inflorescences; fruits glabrous, papillose, or uncinate-hispid; annual or perennial.

    3 Stems retrorsely scabrous; annual.

      4 Fruits and ovaries sharply papillose; flowers and fruits mainly in clusters of 3

      4 Fruits and ovaries smooth or with hooked bristles; flowers and fruits mainly in clusters of 2-5.

        5 Flowers white, 2-3.5 mm in diameter; pollen grains 25-30 microns (μ) in polar diameter; fruits usually 2.8-4 mm long (excluding the bristles when present) but occasionally smaller; fruits with bristles (very rarely smooth), the bristles with bulbous bases; stem nodes usually tomentose but sometimes almost glabrous; leaves linear-oblanceolate, lax, to 50 mm long and 5 mm wide

        5 Flowers greenish-yellow, 0.8-1.5 mm in diameter; pollen grains to 24 microns (μ) in polar diameter; fruits 1.5-2.8 mm long (excluding the bristles, when present); fruits smooth or with bristles, the bristles wider at the base but not bulbous; stem nodes glabrous or lightly pubescent; leaves narrow, linear-lanceolate, mucronate, firm textured, to 40 mm long and 3 mm wide

    3 Stems glabrous or pubescent, but not scabrous; perennial.

          6 Fruits and ovaries uncinate-hispid; nodes bearded, the stem otherwise glabrous; [section Hylaea]

          6 Fruits and ovaries glabrous; nodes not bearded, the stem either glabrous or pubescent toward the base of the plant.

             7 Corolla 3-5 mm across, the pedicels usually shorter than the width of the corolla; inflorescence branches ascending, mostly at < 45 degrees

             7 Corolla 2-3 mm across, the pedicels usually longer than the width of the corolla; inflorescence branches spreading, mostly at > 45 degrees