Photo Credit: Leslie Mehrhoff, University of Connecticut, Retrieved from Bugwood.org (Image Number: 5447655), used under CC BY 3.0 US, modified from the original
Giant knotweed is native to northern Japan. It was introduced into North America as an ornamental due to its size and white flower clusters.
This species forms dense stands that shade and crowd out native vegetation causing a loss or alteration of wildlife habitat, especially along waterways. It can also sprout through asphalt and small cracks in concrete causing structural damage to foundations and roads.
Giant knotweed has small white flowers that are 3-5 mm wide and are clustered together in showy often upright sprays along the branches.
The large leaves are heart-shaped and grow up to 45 cm long and 40 cm wide. The undersides of leaves are covered in soft, 0.2-0.6 mm long hairs.
The stems are round and hollow and grow up to 4 m tall.