What does it look like?
Asiatic knotweed is a thicket-forming herb that can grow to 2m tall. It has zig-zagging stems and red-purple shoots which appear early in spring. As the canes grow, the leaves unfurl and the plant turns green. The mature canes are hollow and have a characteristic pattern of purple speckles. The leaves are long, triangular (15 x 10cm) and pointed at the tip, with a flattened leaf base. In late summer it produces masses of creamy white flowers.
Asiatic knotweed grows primarily in disturbed areas, urban sites, roadsides and along riparian margins. It can tolerate a wide range of soil conditions, high temperatures, high salinity and drought but its growth is depressed by shade.
Why is it a problem?
Asiatic knotweed spreads rapidly, forming dense stands that compete with native vegetation. Its tough shoots and roots can break through gravel, tarmac and concrete; causing damage to foundations, walls, pavements, drainage works, and flood prevention structures.
Its dead stems and leaf litter decompose very slowly, forming a deep organic layer and prevents native seeds from germinating. Asiatic knotweed reproduces from seed and can regrow from detached or broken fragments of roots or stems.