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Key to Senecio

Asteraceae

Senecio

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1 Stems erect, usually 1, 5-24 dm tall; ray flowers absent; disk flowers white to ochroleucous or greenish, rarely pinkish; cypselae 8- to 12-ribbed.
1 Stems erect to lax, 1 or clustered, 1-12 dm tall; ray flowers absent or present; disk flowers usually yellow; cypselae usually 5-ribbed or -angled.
      4 Subshrubs; herbage glabrous; stems usually multiple, branching upwards
      4 Annual; herbage glabrous or tomentose; stems single.
        5 Ray flowers 0; calyculi bractlets black-tipped; [exotic, widespread]
        5 Ray flowers 8; calyculi bractlets not black-tipped; [natives, AR, LA, OK, TX].
          6 Plants 3-7+ dm; herbage loosely arachno-tomentose, unevenly glabrate or glabrescent; mid-stem leaves lanceolate, 3-10 cm (bases tapered or truncate, sometimes clasping)
          6 Plants 8-12 dm; herbage glabrous or glabrate; mid and upper leaves ovate to broadly lanceolate, 10-20 cm (bases clasping)