Japanese knotweed (also known as crimson beauty, Mexican bamboo, Japanese fleece flower, or Reynoutria) is a non-native, invasive species. Introduced to the U.S. from East Asia in the late 1800s, knotweed was originally used as a for erosion control and ornamentally. This aggressively growing herbaceous perennial often occurs in large monocultures and can reach heights of 10 feet.
Stems of Japanese knotweed are smooth, stout and swollen at joints where the leaf meets the stem. Leaves are typically about 6 inches long and 3 to 4 inches wide, somewhat triangular and pointed at the tip. Minute, greenish-white flowers occur in late summer that produce small, winged fruits.
Japanese knotweed spreads primarily by vegetative means with the help of its long, stout rhizomes. The plant spreads quickly to form dense thickets that exclude native vegetation. Japanese knotweed spreads quickly to form dense thickets that exclude native vegetation and greatly alter natural ecosystems. Japanese knotweed can tolerate a variety of adverse conditions including full shade, high temperatures, high salinity and drought.
Knotweed can quickly become an invasive pest in natural areas as well as landscapes and can be found along streams and rivers, in low-lying areas, along rights-of-ways, and can be found in the city as well as suburban areas. Escapees from neglected gardens and discarded cuttings are common routes of dispersal from urban areas. Once established, populations are extremely persistent.
Grubbing is effective for small initial populations. Juvenile plants can be hand pulled depending on soil conditions and root development. However any portions of the root system not removed will potentially resprout. All plant parts pulled should be bagged and disposed to prevent inadvertent spread.
Perhaps the most effective management technique to control large established stands of Japanese knotweed is through a combination of cutting and chemical control. Manual control alone is not an effective long-term control method and may actually exacerbate the problem by encouraging new growth from rhizome segments. Several years of treatment may be needed for well-established populations.
If you are unsure how to properly identify the plant or want help controlling its spread, contact BTSE and we can develop a program to help keep your property free of this aggressively invasive plant.