japanese knotweed plant

Japanese knotweed – Fallopia japonica

Fallopia japonica 

Polygonaceae (Smartweed family)

MI Status


Life cycle

Aggressive, clump-forming perennial.


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


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.


Seeds and aggressive rhizomes.

Similar weeds

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

Japanese knotweed foliage and flowers
Japanese knotweed foliage and flowers
Japanese knotweed flower
Japanese knotweed flower
New ocrea
New ocrea

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