Japanese Knotweed

Naming

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

The invasive root system and strong growth can damage concrete foundations, buildings, flood defences, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channels in flood defences to carry water.

Uses

Japanese knotweed flowers are valued by some beekeepers as an important source of nectar for honeybees, at a time of year when little else is flowering. Japanese knotweed yields a monofloral honey, usually called "bamboo honey" by northeastern U.S. beekeepers, like a mild-flavored version of buckwheat honey.

The young stems are edible as a spring vegetable, with a flavor similar to extremely sour rhubarb. In some locations, semi-cultivating Japanese knotweed for food has been used as a means of controlling knotweed populations that invade sensitive wetland areas and drive out the native vegetation. It is eaten in Japan as "sansai" or wild foraged vegetable.

Similarly to rhubarb, knotweed contains oxalic acid, which when eaten may aggravate conditions such as rheumatism, arthritis, gout, kidney stones or hyperacidity.

Both Japanese knotweed and giant knotweed are important concentrated sources of resveratrol and its glucoside piceid, replacing grape byproducts. Many large supplement sources of resveratrol now use Japanese knotweed and use its scientific name in the supplement labels. The plant is useful because of its year-round growth and robustness in different climates.