Japanese Knotweed

Scientific Name: Polygonum cuspidatum
Family Name: Polygonaceae




Flowers: 1/8 in. (3 mm.) long white individual flower without petals. These flowers form clusters 2 - 3 in. (5 ? 7.5 cm.) in length.

Leaf: 4 ? 6 in. (10 ? 15 cm.) long, ovate leaves tapering to a point.




Plant: 3 ? 7 ft. (90 ? 210 cm.) tall, hollow bamboo like branches and stems.

Identifying Characteristics: Japanese Knotweed is identified by its hollow bamboo stems, and by its flowers which are clusters of papery white ovals.

Location: We found Japanese Knotweed on the Brandeis University campus by the side of the road to the Charles River Apartments.

History and Comments: Japanese Knotweed is native to Asia, and it was introduced to the United States in the 1890's as an ornamental tree. It quickly escaped cultivation, and it is a major weed problem, especially on the Pacific Coast. By 1938, botanists recognized Japanese Knotweed's invasive character and began to publish articles on how to control and eradicate it. Japanese Knotweed prefers wet areas by rivers and lakes and is content to live in the shade, but saplings will grow from concrete or mulch. Young Japanese Knotweed shoots can be boiled and eaten like asparagus.



    Unless otherwise specified, all text, photographs, and drawings are Copyright (c) by Shu-Yee Chen and Deborah Hamer 2003. No part of this page may be reproduced without prior written consent of the authors.