Vascular Plants of North Carolina
Account for Giant Knotweed - Reynoutria sachalinensis   (F. Schmidt ex Maxomowicz) Nakai
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Section 6 » Family Polygonaceae
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Author(F. Schmidt ex Maxomowicz) Nakai
DistributionMostly Mountains, plus Orange County.

Native of eastern Asia; in N.A. Newf. to Ont. and WI, south to NC and TN; also LA. Also B.C. and MT south to ID and CA.
AbundanceVery rare.
HabitatRoadside banks, ditches, creek banks.
PhenologyFlowering and fruiting July-October.
IdentificationGiant Knotweed is more robust than Japanese Knotweed (R. japonica), attaining heights of 6-12 feet (or more). The leaves are similar but larger and with a cordate (not truncate) base. The inflorescences are similar to those of Japanese Knotweed -- narrow white racemes that are mostly erect.
Taxonomic CommentsNamed as Polygonum sachalinense in older references. A hybrid between R. japonica and R. sachalinensis has been reported from the NC mountains. See Weakley (2018) or FNA for ID criteria.

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State RankSE
Global RankGNR
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