Vascular Plants of North Carolina
Account for Mile-a-minute-weed - Persicaria perfoliata   (L.) H. Gross
Members of Polygonaceae:
Members of Persicaria with account distribution info or public map:
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Section 6 » Family Polygonaceae
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Author(L.) H. Gross
DistributionTo date collected a few times in Alleghany County in 2008-2010 and once in Rockingham County in 2008 by Mengchi Ho. To be looked for in other northern or montane counties.

Native of Asia; in N.A. RI to OH and south to NC; also MS, OR.
AbundanceVery rare. However, one population in Alleghany County had 1000+ plants in 2010. This aggressive alien has been declared a noxious weed in a few states, and it is important that all NC occurrences be eradicated.
HabitatDisturbed roadside banks and drainage ditches.
PhenologyFlowering and fruiting July-September.
IdentificationMile-a-minute-weed is so named for its ability to spread rapidly and also its ability to grow to large size (20 feet long or so) in a single growing season. It is an annual vine that spreads laterally with support of other vegetation. The stems have an abundance of short prickles. The leaves are long-stalked, broadly triangular, and peltate near the margin. The collar (ocrea) where the leafstalk meets the stem usually has a roundish, leafy projection that encircles the stem. Inflorescences are short spikes or heads.
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).
Other Common Name(s)Asiatic Tearthumb
State RankSE *
Global RankGNR
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