Vascular Plants of North Carolina
Account for Himalayan Knotweed - Persicaria wallichii   Greuter & Burdet
Members of Persicaria with account distribution info or public map:
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Section 6 » Family Polygonaceae
AuthorGreuter & Burdet
DistributionA single population is known for NC: Haywood County, US route 23/74 at railroad grade just N of Balsam Gap. First collected by D. Pittillo in 2002, then by R. Lance in 2007.

Native of the Himalayan region; in N.A. in St. Pierre et Miquelon, MA, NC, CA, OR, B.C.
AbundanceVery rare.
HabitatRoadside near railroad.
PhenologyFlowering and fruiting September-October.
IdentificationHimalayan Knotweed is a perennial up to 3 feet tall. It has very long (4-9 inches) leaves with acuminate tips. The leaves tend to occur in one plane on the branches. The inflorescences are in upper axils and terminal, and are branched. The flowers are white or pinkish.
Taxonomic CommentsMany species formerly treated in the genus Polygonum have been moved to Persicaria, the smartweeds. These are generally erect and tall plants with terminal and axillary floral spikes; most occur in wetlands. Others remain in Polygonum, the knotweeds, which are generally prostrate to ascending and with inconspicuous axillary flowers. They occur mostly in dry soils and tend to be weedy.

Attention must be paid to the small collars at the junction of the main stem and leaf stems (called ocreae) and whether they possess terminal hairs or bristles. Some keys also refer to the even smaller collars from which flowers emerge (called ocreolae). Another important ID character is the surface of the greenish sepals -- whether smooth or dotted with indentations (punctate).
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State RankSE
Global RankGNR
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