Knotweed, commonly known as Japanese knotweed, is a perennial plant that originated in the Far East, including Japan, Korea and China. The herbaceous plant is also common in North America and Europe, where it's considered to be an invasive species. Japanese knotweed is part of the Polygonaceae family.
Japanese knotweed is a shrub-like, upright perennial that can be up to 10 feet tall. Its stem is smooth, stout and hollow and has elevated nodes that closely resemble bamboo. Japanese knotweed is characterized by broad, oval leaves (sometimes triangular) that have truncated bases. The flowers of knotweed are small and have a creamy, milky white color.
Japanese knotweed first came to the United States in the late 19th century. It now grows in 36 states. In the United States, Japanese knotweed is capable of tolerating a vast array of difficult conditions, including high temperature, full shade, salinity and drought. Japanese knotweed appears alongside rivers and streams, in areas of waste and in low-lying areas.
Due to its rapid growth and invasive root system, Japanese knotweed can damage roads, flood defenses, walls, buildings and architectural sites.
There are various different uses for Japanese knotweed. Its young stems are often consumed as spring vegetables and are often compared in taste to mild rhubarb. Knotweed is also commonly used by beekeepers as nectar for honeybees. It provides a concentrated source of resveratrol, which functions as a substitute for grape byproducts.
Japanese knotweed can be eaten as a vegetable, but it must be done so with caution. This is because the plant contains oxalic acid, which is capable of disturbing several medical conditions, including arthritis, rheumatism, gout, hyperacidity and kidney stones.
In general, Japanese knotweed spreads via vegetative means with assistance from its stout rhizomes. Japanese knotweed is often brought to new areas as a contaminant in fill-dirt seeds. It is also sometimes brought to new areas by water or the wind.
Other names that are used for Japanese knotweed include Himalayan fleece vine, Mexican bamboo, fleeceflower, Huzhang, monkeyweed, elephant ears, Hancock's curse, Japanese bamboo, sally rhubarb, donkey rhubarb, pea shooters, American rhubarb, Reynoutria and crimson beauty. The Japanese word for the plant is "itadori."