Giant knotweed, native to parts of Eastern Asia, has spread substantially beyond its original range. Introduced predominantly in regions across Europe and parts of Southern Africa, it has also established itself in New Zealand. Giant knotweed's extensive colonization is notable particularly in temperate areas of the Northern Hemisphere.

Native to Japan, giant knotweed has spread throughout the world and is widely considered invasive. It is listed as an invasive species throughout much of the United States. Its ability to spread laterally through rhizomes as well as root fragments allows it to spread rapidly, especially via water in riparian areas. It tolerates a wide variety of soils and light levels but is intolerant to dry conditions. Once established, it can grow up to 5 cm a day and forms a dense layer of leaves. Herbicides can be effective but have limited usability near water, so they cannot be used for many infestations. Repeated digging, mowing, and grazing can also effectively control giant knotweed. In some areas, giant knotweed is cultivated to produce pest management products and for bioaccumulation.

The best season for removal of giant knotweed is during late spring or early summer, before it reaches its mature flowering stage. Here are a few methods of controlling this plant: