The rhizome is the direct cause of the spread of Japanese knotweed. In fact, these rhizomes can grow up to 2m deep and 7m wide, under the ground. When split open, internally, the rhizome will appear orange. On the other hand, externally, the rhizome has a ‘knotty’ and ‘woody’ resemblance.
However, it is important to know that the rhizome of Japanese knotweed in Autumn can remain dormant for up to 20 years and the regeneration can start from a piece of the plant that is as small as 0.7g. Which is only about 2/3 as heavy as a jelly bean!!