Japanese knotweed - idenitfy in MI nurseries

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Japanese knotweed - Polygonum cuspidatum Sieb. & Zucc

Japanese knotweed flower cluster.

Japanese knotweed foliage.

Similar weeds: Giant knotweed (P. sachalinense F.W. Schmidt) Differs by having a greater height and heart-shaped leaf base.

Life cycle: Aggressive, clump-forming perennial.

Leaves: Alternate, broadly egg-shaped, sometimes heart-shaped with a squared leaf base.

Stems: Stout, semiwoody, red to brown, hollow and bamboolike, often exceeding 6 to 8 feet in height. Stems are also jointed, forming a zigzag growth pattern. A membranous sheath (ocrea) surrounds the stem at the base of each petiole. Reddish shoots arise from thick, sturdy and abundant rhizomes.

Flowers and fruit: Flowers are small, white to pink and borne in elongated clusters. The seed is enclosed in a single-seeded, shiny, dark brown to black, three-sided fruit.

Reproduction: Seeds and aggressive rhizomes.


Japanese knotweed foliage and flowers.	Japanese knotweed ocrea.

The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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02/08/08