What Does Japanese Knotweed Look Like?

Written by joan reinbold
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Introduced to the United States in the 1800s, the Japanese knotgrass is an invasive perennial shrublike plant native to eastern Asia. Its common names include Mexican bamboo, fleeceflower and huzhang.


Japanese knotgrass generally grows three to nine feet in height. Sometimes it grows over 10 feet in height.


The stems of the Japanese knotgrass are red, hollow, stout, smooth and jointed. At the joints connecting the stems with the leaves, the stems are swollen.


Leaves of the Japanese knotgrass are pointed at the tip, feature reddish veins and range from triangular to oval in shape. They average six inches in length and three to four inches in width.


The roots of the Japanese knotgrass are usually 15 to 18 feet long and they are also thick. The roots are the primary way the Japanese knotgrass spreads.


Japanese knotgrass flowers are small and range in colour from white to green-white. They bloom in late summer, and grow in branching sprays near the outer part of the stems.


After the flowers bloom, the Japanese knotgrass produces black winged fruits, with shiny seeds that are triangular and one-tenth of an inch long.

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