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

Japanese knotweed (Fallopia japonica) - Governor's Island - West Point

Date First Found
Location First Found
Located at the base of Rocky Roost, a small point off the west side of Governor's Island. Part of point is owned privately and part is Mendota Mental Health Institute grounds. Take the main path to Rocky Roost, the largest patch will be evident to your left toward the beach. There is a smaller patch to the right toward a marshy area. Last year the plant were quite tall. They seem to have established new ground near the beach.
Original Extent
One or a few beds

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.