Japanese Knotweed

(Polygonum cuspidatum)

 

   

 

 

Color Photograph: Copyright Nearctica.com, Inc.

Line Drawing: Britton, N.L., and A. Brown. 1913. An Illustrated Flora of the Northern United States and Canada, Second Edition.

 

Japanese Knotweed (Polygonum cuspidatum Sieb. and Zucc.)

Alien: Native of Japan.

Identification: A tall, rank, weedy species, perennial and becoming woody in its lower parts. Flowers white, small, loosely clustered in long, branched spikes. Stem green, becoming woody near the base of the plant, and with swollen nodes at the interception of a leaf petiole and the stem. Leaves large, ovate, with an acute apex, and a long petiole.

Distribution: Throughout most of North America except for the southwestern United States.

Habitat: Japanese Knotweed has escaped from cultivation and is found in a variety of disturbed habitats included fields, forest margins, roadside ditches, and fields.

Flowering period: July to October.

Similar Species: The swollen nodes on the stem, the broad leaves, and the branched spikes of white flowers are distinctive.

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