Biology & Ecology

  • Knotweeds are members of the Buckwheat Family (Polygonaceae) that originate from volcanic regions of Asia
  • All species of knotweeds are extremely fast growers, reaching heights of 6 -15 within a single growing season. Plants usually attain their full height by June - July, and go to flower in July/August
  • Growth typically starts in early April, but may start later at higher elevation
  • Commons names often include False Bamboo, Elephant Ear, and Fleeceflower
Scientific Names
Scientific names include:
  • Bohemian knotweed (Polygonum X bohemicum)
  • Giant knotweed (Polygonum sachalinense)
  • Himalayan knotweed (Polygonum polystachyum)
  • Japanese knotweed (Polygonum cuspidatum)
  • Depending on the size, age, and site location of the plant, rhizomes can penetrate up to 7 feet into the soil, making control very difficult
  • Flowers are grown out of leaf axils, and are white to greenish in color
  • Leaves are alternate and bright green
  • Manual control activities tend to aggravate the plant
  • Plants can send up young shoots late into the growing season, especially in response to treatment activities
  • Plants die back after the first major frost of the year
  • Rhizomes are brittle and orange in color, much like that of a carrot
  • Rhizomes can send out shoots up to 20 - 25 feet away from the mother plant
  • Stems are thick and hollow, resemble bamboo, and are green to reddish in color
  • Tall, very aggressive perennial species
  • While plants are dormant for the winter, the dead brown canes persist throughout the winter months, creating an unattractive landscape

Life Cycle of Knotweed

The lifecycle of knotweed