The term 'Invasive Japanese Plant' refers to Knotweed, an 8-letter plant native to East Asia. It is an aggressive and highly invasive species that has spread throughout the world, causing significant damage to ecosystems and infrastructure. Knotweed is a perennial plant with hollow stems and small white flowers, and it can grow up to 10 feet tall. It is difficult to control and can quickly take over an area, making it a major problem for land managers.