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Knotweed Species

General Infomation

Annual or perennial dicots with broad distribution.


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Species Data


May be found in shallow water to moderately dry soil in aquatic and agricultural sites. Some species may be somewhat emersed.


Simple and alternate.


Green, pink, or white spikelike racemes borne on jointed stalks. May be axillary or terminal depending up on species.


Swollen at the nodes, and green to red in color. Of note: the presence of ocrea (a white membranous sheath particular to the Polygonum genus) at the juncture of each stem and leaf.

Similar Species

Alligatorweed lacks an ocrea and the flower is not a spike.

Aquatic Plants App

Whether you're a professional botanist or a casual nature enthusiast, the NC State University (NCSU) Aquatic Weeds app has detailed information on a wide variety of aquatic weeds to assist in identification.