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Key to Fallopia

Polygonaceae

Fallopia

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1 Ocreae reflexed bristly at the base; perianth white; achene glossy black; [of high elevation openings and woodlands]
1 Ocreae smooth; perianth greenish to yellowish or pinkish; achene glossy or dull black; [mostly of lower elevations].
(c) Wang, Zihao - CC-BY
  2 Plant woody; inflorescences freely branched, strongly paniculate; [sometimes cultivated, apparently naturalizing]; [section Sarmentosae]
  2 Plant herbaceous; inflorescences less-branched, usually a reduced panicle with only a few racemose branches; [collectively common and in various natural and disturbed habitats]; [section Fallopia].
    3 Achene dull black; outer sepals keeled, not expanding into obvious wings in fruit, the fruit therefore 3.5-4.5 mm long (measured from the pedicel joint to the tip); [weedy annual]
    3 Achene glossy black; outer sepals expanding into obvious wings in fruit, the fruit therefore 7-15 mm long (measured from the pedicel joint to the tip); [native perennial or weedy annual].
      4 Fruiting perianth wings usually truncate to attenuate-decurrent on stipelike base, flat, or (less often) undulate or crinkled, margins entire (rarely undulate-crenate)
      4 Fruiting perianth wings decurrent on stipelike base, undulate or crinkled, rarely flat, margins wavy-crenulate to incised or lacerate (rarely entire)