Weed ID

KNOTWEED COMPLEX

Polygonanceae or Buckwheat Family
Polygonum cuspidatum, sachalinense & polystachyum

KNOTWEED COMPLEX SPECIES: Japanese, Giant, and Himalayan Knotweed.

GROWTH HABIT: Herbaceous, shrub-like perennial that grows to heights in excess of 10 feet.

LEAVES: Six inches long, and 3 to 4 inches wide, broadly oval to somewhat triangular, mostly pointed at the tip, and are alternate on the stems.

STEMS: Smooth (bamboo-like), stout, and swollen at the joints where the leaf joins the stem. Stems are hollow, but may be water-filled depending upon soil moisture levels and where it is growing.

FLOWERS: Small, pale greenish-white flowers.

ROOTS: Rhizomes may extend 30 feet in length. Buds along the length of rhizomes may develop into new stems depending upon environmental and cultural conditions. Digging around the base of established plants encourages new vegetative buds to develop along the rhizome system.

SEEDS: Seeds are triangular, shiny, very small about 1/10 inches long. Seeds are not viable outside its native range of Asia.

REPRODUCES: Spreads by sprouts from rhizomes of established plants and from sprouts arising from stems that have been severed from the mother plant.

HABITAT: Riparian areas, upland sites, irrigation ditches, and road-rights-of-way.