Fallopia japonica
Japanese knotweed (Fallopia japonica) is an herbaceous perennial plant from Asia. In 1825 it was introduced from Japan to the United Kingdom as an ornamental plant. Knotweed was then brought to North America in the late 1800s for use in landscaping and erosion control. One of the worst invasive species in the world, Japanese knotweed can thrive in many places, harm native habitats, and even damage the foundations of buildings.
Japanese knotweed is typically found in wet soils in lowlands, wetlands, and along streams. It tolerates a wide range of growing conditions, including full sun, high salinity, and dry soil. Now scattered throughout Missouri, Japanese knotweed grows along rivers, streams, roadsides, utility rights-of-way, and crop fields.
It has large, heart-shaped leaves, pointed at the tip (3 to 6 inches), and grows 3 to 12 feet tall with a shrublike appearance. Sheathlike coverings and swollen nodes are found where the leaf meets the stem. It has white-to-greenish flower clusters in midsummer and small, winged seeds by August and September.
A foliar herbicide solution may be applied before seed formation in early summer and in the fall, often as a re-treatment. Effective herbicides include triclopyr, glyphosate, imazapyr, and picloram, used separately or in combination. Because knotweed thrives in streamside areas, choose herbicide based on location of plants and presence of non-target vegetation. Do not use triclopyr and picloram in wetlands or adjacent to water. If the foliar spray is not practical, try cutting along with use of herbicides. Cutting will remove the above-ground plant and stimulate the rhizomes below ground, so follow-up with herbicides is necessary.
Prescribed burning can also help control it, and in some cases, kill it, along with other invasive herbaceous plants like spotted knapweed and teasel rosettes, which are green in winter.
See this MDC Japanese knotweed page for more details.
Identification and fact sheets
- Learn about Japanese knotweed at Invasive.org
- Learn about identification, threats, and control practices of Japanese knotweed from the Missouri Department of Conservation
Representative photos of Japanese knotweed:
Japanese knotweed impact, abundance, and trend in Missouri
