T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Fallopia japonica (Japanese knotweed)

Kingdom:   Plantae
(Unranked):        Angiosperms
(Unranked):        Eudicots
(Unranked):        Core eudicots
Order:       Caryophyllales
Family:      Polygonaceae
Genus:      Fallopia
Species:     F. japonica
Binomial name:  Fallopia japonica
Synonyms: Polygonum cuspidatum, Reynoutria japonica
Common names:  Japanese knotweed, Asiatic Knotweed, Fleeceflower, Himalayan fleece vine, Monkeyweed, Monkey fungus, Hancock's curse, Elephant ears, Pea shooters, Donkey rhubarb, Sally rhubarb, Japanese bamboo, American bamboo, Mexican bamboo (though it is not a bamboo).

Fallopia japonica is listed by the World Conservation Union as one of the world's worst invasive species.

It is a large, herbaceous perennial a native to Eastern Asia in Japan, China and Korea. In North America and Europe the species is very successful and has been classified as an invasive species in several countries. Fallopia japonica has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not closely related. While stems may reach a maximum height of 3–4 m 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 long and 5–12 cm broad, with an entire margin. The flowering occurs December, January, February and March. They are small, cream or white and produced on racemes (15 cm long) which are initially erect but droop at maturity.

The invasive root system and strong growth can damage concrete foundations, buildings, flood defenses, roads, paving, retaining walls and architectural sites. It is a frequent coloniser of temperate riparian ecosystems, roadsides and waste places. It forms thick, dense colonies that completely crowd out any other herbaceous species and is now considered one of the worst invasive exotics in parts of the eastern United States. The success of the species has been partially attributed to its tolerance of a very wide range of soil types, pH and salinity. Its rhizomes can survive temperatures of −35 °C and can extend 7 metres horizontally and 3 metres deep, making removal by excavation extremely difficult.

Photo below of an empty section covered in Fallopia japonica.








Photographed March New Plymouth.




The underside of a leaf.