Japanese Knotweed

Reynoutria japonica in bloom

Polygonum cuspidatum, Reynoutria japonica, Fallopia japonica

Synonyms:
Hu Zhang

Reynoutria japonica
Reynoutria japonica in Brastad 1.jpg
Scientific classification edit
Kingdom:Plantae
Clade:Tracheophytes
Clade:Angiosperms
Clade:Eudicots
Order:Caryophyllales
Family:Polygonaceae
Genus:Reynoutria
Species:
R. japonica
Binomial name
Reynoutria japonica
Synonyms
  • Fallopia compacta (Hook.f.) G.H.Loos & P.Keil
  • Fallopia japonica (Houtt.) Ronse Decr.
  • Pleuropterus cuspidatus (Siebold & Zucc.) H.Gross
  • Pleuropterus zuccarinii (Small) Small
  • Polygonum compactum Hook.f.
  • Polygonum cuspidatum Siebold & Zucc.
  • Polygonum hachidyoense Makino
  • Polygonum reynoutria Makino
  • Polygonum zuccarinii Small
  • Reynoutria hachidyoensis (Makino) Nakai
  • Reynoutria hachijoensis Nakai ex Jôtani
  • Reynoutria hastata Nakai ex Ui
  • Reynoutria henryi Nakai
  • Reynoutria uzenensis (Honda) Honda
  • Reynoutria yabeana Honda
  • Tiniaria japonica (Houtt.) Hedberg

Reynoutria japonica, synonyms Fallopia japonica and Polygonum cuspidatum, is a species of herbaceous perennial plant of the knotweed and buckwheat family Polygonaceae. It is commonly known as Asian knotweed or Japanese knotweed. It is native to East Asia in Japan, China and Korea. In North America and Europe, the species has successfully established itself in numerous habitats, and is classified as a pest and invasive species in several countries.

Japanese knotweed has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not related. While stems may reach a maximum height of 3–4 m (10–13 ft) each growing season, it is typical to see much smaller plants in places where they sprout through cracks in the pavement or are repeatedly cut down. The leaves are broad oval with a truncated base,7–14 cm (3–5+12 in) long and5–12 cm (2–4+12 in) broad, with an entire margin. The flowers are small, cream or white, produced in erect racemes6–15 cm (2+12–6 in) long in late summer and early autumn.

Related species include giant knotweed (Reynoutria sachalinensis, syns. Fallopia sachalinensis, Polygonum sachalinense) and Russian vine (Fallopia baldschuanica, Polygonum baldschuanicum).

Dead stems from previous years remain in place as new growth appears.
A hedgerow made up of roses and Japanese knotweed in Caersws, Wales, in 2010
Erect inflorescence
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