👉 Ctenobryum is a genus of flowering plants in the family Fabaceae, commonly known as the Japanese knotweed or black knotweed. These plants are native to Japan and China, but they can also be found on islands such as Taiwan, which they were introduced there for the sake of cultivation. Ctenobryum are typically small, woody plants with a long stem that grows up to 10 feet (3 meters) tall. They have large, fleshy