Knotweed refers to a group of perennial plants in the genus Fallopia, commonly known for their rapid growth and invasive nature. The most notorious species, Japanese knotweed (Fallopia japonica), can grow up to 10 feet tall and has hollow stems resembling bamboo. It thrives in various environments, often disrupting local ecosystems and damaging infrastructure. Knotweed is challenging to control due to its extensive root system, which can spread underground. It is often found in urban areas, along riverbanks, and in disturbed sites. Effective management typically requires professional intervention and can involve methods like herbicide application or physical removal.