Japanese knotweed is an invasive herbaceous perennial that forms large dense clumps of a stout, shrub-like plant between 3-9 feet tall. The stems are reddish in color, ridged, jointed and hollow. When the South River remediation team attempted to repopulate the South River riverbanks with native species, controlling the Japanese knotweed was a challenge. Not only is it hardy, but Japanese knotweed can grow up to 4 inches in a day. Its dense summer foliage can block the sun and slow native plant growth. The team removed it by hand and applied targeted herbicide (by spraying and injecting). It is still a challenging species to control.
