1 Stems strongly winged by decurrent leaf bases

1 Stems not strongly winged by decurrent leaf bases (but may be ribbed).

  2 Leaves petiolate or narrowly cuneate at the base; [section Pluchea].

    3 Plant a shrub, 10-40 dm tall; leaf margins entire or inconspicuously denticulate with callous-tipped teeth; [peninsular FL and s. TX southwards]

    3 Plant an annual or perennial herb, 5-20 (or more) dm tall; leaves conspicuously serrate; [collectively widespread in our region].

      4 Phyllaries glandular on the outer surface (the outer bracts also somewhat pubescent); inflorescence paniculiform, the lateral branches not reaching or exceeding the central branches; plants to 20 dm tall; [in freshwater habitats and uplands, widespread inland]

      4 Phyllaries short-pubescent with several-celled glandular-tipped hairs; inflorescence more-or-less corymbiform and flat-topped, some of the lower lateral branches elongate and reaching or exceeding the central branches; plants to 10 (-15) dm tall; [mainly in salty or brackish habitats, restricted to the outer Coastal Plain]

        5 Plants to 10 (-15) dm tall; involucres 4-5.5 (-6) mm high, the disks 4-7 (-8) mm in diameter; [e. VA south and west to s. FL, se. TX, and beyond]

        5 Plants usually < 6 dm tall; involucres 5.5-7 mm high, the disks 5-9 mm in diameter; [e. NC northwards to MA]

  2 Leaves sessile, and either rounded, truncate, or clasping at the base; [section Amplectifolium].

          6 Leaves mostly 8-20 cm long and 3-7 cm wide; involucre 9-12 mm high; middle phyllaries 2.5-3 mm wide

          6 Leaves mostly 3-10 cm long and 1-3 cm wide; involucre 5-10 mm high; middle phyllaries 1-1.5 mm wide.

             7 Stems and leaves glandular, otherwise nearly glabrous; involucre 4-5 mm wide

             7 Stems and leaves puberulent or arachnose as well as glandular; involucre 5-12 mm wide.

               8 Corollas creamy white; heads 6-10 mm high, 6-12 mm wide; phyllaries thinly arachnoid, with sessile glands; outer phyllaries obtuse or obtuse-apiculate; nutlets pinkish, ca. 1 mm long, pubescent on the angles; [flowering late Jul-Oct].

                 9 Plants 3-11 dm tall; inner phyllaries 4-6 mm long; [widespread in our area]

                 9 Plants 9-25 dm tall; inner phyllaries 6-7 mm long; [of the Coastal Plain of SC southward]