...fostering a harmonious relationship between people and the Southern Appalachian environment

JAPANESE KNOTWEED (Polygonum cuspidatum)

Description

• Forms dense stands that reach 10 feet.
• Leaves 2- to 6-inches long and heart-shaped.
• Stems are bamboo-like (hollow), light green to purplish-red, smooth, and swollen at joints where leaves are attached.
• Small flowers are white to greenish-white in small sprays along smallest branches.
• Origin--Japan

Distribution

• Spotty distribution in all counties along home sites, streams, low-lying areas, and rights of way.
• A few stream banks heavily invaded.
• Prefers moist areas with disturbed soil.

Threat

• Dense thickets crowd native vegetation. Tolerates adverse growing conditions.
• Quickly expands in natural areas from cultivated sources.
• Threatens riparian areas where it is rapidly colonizing scoured shores and islands.

Control

• Hand pull small plants.
• Grub larger plants removing roots (rhizomes) and other plant parts.
• Foliar spray with glyphosate or triclopyr (2%) during growing season.
• Treat cut plants with 25% solution to knock down plants for easier foliar spraying when new sprouts and leaves emerge.

Similar Plants

• Redbud has similar leaf, but lobes at leaf base rounded where knotweed leaf base is flat. Redbud has a solid, woody twig.

Links to sites with additional information on Japanese Knotweed

• PCA Alien Plant Working Group--Japanese Knotweed
• Invasivespecies.gov--Japanese Knotweed
• The Nature Conservancy's Invasives on the Web--Japanese Knotweed
• USDA Forest Service's Pest Alert--Japanese Knotweed
• Southeast Exotic Pest Plant Council--Japanese Knotweed

References: Southeast Exotic Pest Plant Council