BACKGROUND: Native to Asia, Japanese knotweed is an escaped ornamental found along roadsides and waterways, in waste areas, and pastures. It forms thick stands and is also shade tolerant. Dormant plants can be a fire hazard.
OTHER COMMON NAMES: Fallopia japonica
DESCRIPTION: A creeping herbaceous perennial with hollow, reddish- brown, jointed stems. The plant grows 2.5-10 feet tall. Leaves are oval to heart-shaped. Tiny cream-colored flowers are borne in loose, branching clusters. Rhizomes can grow 30 feet long and form dense tangles. New plants can also regenerate from rhizome fragments.
CONTROL: When digging, the entire rhizome must be removed. Repeated mowing over a period of several years depletes the rhizomes. Japanese knotweed has been shown to have medicinal properties, for which it could potentially be harvested. Some herbicides can be effective.
- SCIENTIFIC NAME: Polygonum cuspidatum
- CLASS: 1B
- BIOCONTROL AGENTS AVAILABLE: NO