Is this Knotweed a giant of a problem? Similarly Japanese Knotweed’s giant cousin can cause problems to properties. It has the same potential to cause damage and devalue land. How can you tell the difference? Firstly, it’s much taller and can grow to 4m. Also, the leaves are much larger, they tend to be rounder with ruffled edges and a slightly deeper green. The good news, because of the larger leaf size we have had great results with our Management Plans and herbicide treatments. Finally, root barriers, herbicide plans and excavations are also successful.