mid- to late summer
1 to 2 ft.
6 to 10 ft.
sun to partial shade
USDA zones 5-9
Japanese knotweed is a fast-growing, deciduous groundcover with creeping roots. It is an aggressive spreader with green heart-shaped leaves that turn red in the fall. In late summer, clusters of small, pink flowers appear.
Consider this plant's aggressively spreading nature before planting it. It can be an appropriate plant to cover the soil in an area bounded by concrete, but will invade other areas if there is no root barrier.
Japanese knotweed was planted in the Xeriscape Demonstration Garden many years ago. Its flowers are rather inconspicuous.
It is a very aggressive spreader, so it has been removed from all locations except in a parking lot island surrounded by concrete. It took several herbicide applications to kill. Although it is a resilient plant, it is not very attractive in winter.
Cut stems to ground level in late winter before new growth begins in spring. The new growth arises from the roots, not last year's stems.