Vascular Plants of North Carolina
Account for Erect Knotweed - Polygonum erectum   L.
Members of Polygonaceae:
Members of Polygonum with account distribution info or public map:
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Section 6 » Order Polygonales » Family Polygonaceae
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DistributionScattered over the Mountains and northern Piedmont; also one collection in the Coastal Plain (Greene County).

Occurs over much or most of the U.S. and southern Canada, south to central NC, central AL, and NM. NC lies at the southeastern edge of the range.
AbundanceThough common to the north and northwest of NC, in NC it is poorly known, probably under-collected, and certainly overlooked. Rare to uncommon, and extremely rare in the Coastal Plain (if still present). This is a Watch List species. It is probably not as rare as the NCNHP's S1S2 rank, but there seem to be few if any recent SERNEC collections, and iNaturalist has no photos -- correct or unidentified. Thus, its current status is a near complete unknown. This species might truly be in great decline, as one editor (LeGrand) has not knowingly seen it in the state in 50 years of experience.
HabitatMostly in disturbed wetland sites, such as bottomland openings, wet or damp fields, sand or gravel bars, and vacant or waste lots (but usually where moist).
PhenologyFlowers from June to October, and fruits from July to October.
IdentificationThe species is erect to ascending, and many-branched, growing only to 1 foot tall on average. Leaves are alternate and somewhat elliptical to obovate, about 1 inch long, about 2/5-inch wide, rounded at the tip and tapered to the base. The small white flowers are at the leaf bases. This is an extremely "ordinary"-looking plant, with small flowers not attracting attention; and it typically grows in disturbed floodplains or other damp ground. Owing to its common habitats, it should be eventually collected in many more counties in the northern Piedmont and mountains.
Taxonomic CommentsNone

Other Common Name(s)Upright Knotweed
State RankS1S2
Global RankG5
State StatusW7
US Status
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USACE-empFACU link
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