Polygonum virginianum L. - Virginia Knotweed

Polygonum virginianum plant

Family - Polygonaceae

Stems - To +1m tall, non-woody, hairy above, glabrescent below, erect. The pubescence ferruginous.

Leaves - Alternate, petiolate, pubescent on both surfaces or glabrous below, ovate, to +15cm long, +8cm wide. Ocrea fringed with cilia, pubescent.

Polygonum virginianum ocreaOcrea.

Polygonum virginianum leaf

Inflorescence - Typically a terminal raceme, but some axillary, to 40cm long. Flowers loosely arranged on the inflorescnece.

Polygonum virginianum inflorescence

Flowers - Perianth parts 4, whitish to pinkish, +/-3mm long, acute, glabrous. Stamens typically 4, slightly exserted. Filaments whitish, glabrous, 2mm long. Anthers pale yellow to whitish, -1mm long. Styles 2, persistent in fruit to form a "beak".

Polygonum virginianum flower

Flowering - July - October.

Habitat - Rich, moist woods.

Origin - Native to U.S.

Other info. - This species can be found throughout Missouri. It is easy to identify in the field becasue of its hairy ocrea, big, alternate leaves, and long inflorescences. The plant is very common in shaded, rich areas.
A synonym is Tovara virginiana (L.) Raf.

Photographs taken at the Kansas City Zoo, 7-30-99, and in the Ozark Scenic Riverways, Shannon County, MO., 7-29-04.


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