Contact information
For information on Lakes in Wisconsin, contact:
Division of Water
Bureau of Water Quality
Aquatic Invasive Species Contacts

Japanese knotweed (Fallopia japonica) - JK AOI-IBI East River Mile 2

Date First Found
Location First Found
Banks of East River
Latitude and Longitude
44.48684, -88.00198
Original Extent
A Whole Bay or Portion of Lake

Japanese knotweed (Fallopia japonica)

About Japanese Knotweed

Japanese knotweed, in the buckwheat family, is a perennial that grows to heights of 5-10 feet in large clones up to several acres in size. The arching stems are hollow and bamboo-like, a reddish-brown to tan color;; they die, but remain upright through the winter. Mature leaves are 3-5 inches wide and 4-9 inches long, lighter on the lower surface, and egg to spade shaped;; young leaves are heart-shaped. Lacy 2 inch long clusters of tiny greenish-white flowers are produced in late summer and held upright at the leaf base. Japanese knotweed reproduces occasionally by seed, but spreads primarily by extensive networks of underground rhizomes, which can reach 6 feet deep, 60 feet long, and become strong enough to damage pavement and penetrate building foundations.