What is Knotwood?

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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
  • Last Modified Date: 16 October 2019
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Knotwood is a plant native to Eastern Asia which is treated as an invasive species in most other parts of the world, due to its rapid growth habit and the fact that it chokes out native species extremely effectively. The plant is known by a wide range of alternate names, including knotweed, Mexican bamboo, Japanese knotwood, Hancock's curse, Itadori, and Japanese fleece flower. There are a number of uses for knotwood, although this is poor consolation for people who struggle with the plant in their gardens.

As is sometimes the case in taxonomy, there are conflicting scientific names for knotwood. Many people call it Polygonum cuspidatum, but it may also be referred to as Reynoutria japonica, Fallopia japonica, Pleuropterus cuspidatus, or P. sieboldii, among others. As a general rule, P. cuspidatum is the accepted scientific name for knotwood. The alternate names can be used to trace a history of simultaneous discoveries, erroneous classifications, or attempts to name the plant after prominent botanists.

This perennial plant gets quite large if allowed to grow unchecked, and knotwood will also sprawl wildly across the landscape. It has thick, hollow stalks which are broken into segments by swollen joints which superficially resemble knots or flaws in the parent plant. Knotwood has simple leaves, and white flowers which grow on spindly stalks. Knotwood will grow year round, and if cut back, it will resprout from existing roots, making it very difficult to successfully eradicate.


Originally, knotwood was brought to the West as an ornamental. British and American gardeners liked the look of the plant, as it can be coaxed into a pleasing shape and it stays green for most of the year. However, knotwood quickly got out of control, and on any neglected land, it will take over. This is an especially common problem at dumps and composting facilities in areas which are infested by knotwood, since people throw cuttings into the garbage and they sprout.

The roots of knotwood are used in Traditional Chinese Medicine, where they are known as huzhang roots. Knotwood tinctures may also be known as He Shou Wou, and they are used as general tonics for the blood. The plant is also a source of resveratol, a compound used in some nutritional supplements. In addition, the tender young stems of knotwood are edible, and they can be prepared much like rhubarb. Despite these useful applications, many organizations which promote native plants urge gardeners to consider alternatives to knotwood if they are thinking about planting it, since it is so difficult to control.


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