Japanese Knotweed Facts

Japanese knotweed is a strong, fast-spreading invasive weed with tall, dense annual stems.

Read more: What is Japanese Knotweed?

Unsurprisingly, Japanese knotweed originated in East Asia – specifically in places like Japan, China and Korea.

Japanese knotweed was brought to the UK as an ornamental plant in the early 19th century by German physician Philipp Franz von Siebold. Beloved by botanists at first, knotweed eventually spread into the wild and become a persistent pest within the British ecosystem.

Read more: How Japanese Knotweed Came to Europe

Japanese knotweed can be identified by a number of features. During the spring, reddish-purple fleshy shoots appear from crimson-pink buds at ground level, which grow quickly, creating dense stands of tall bamboo-like canes which grow to 7 feet tall. Japanese knotweed leaves are shovel-shaped and grow up to 5 and a half inches long, with a zig-zag pattern along the stems.

Japanese knotweed is not poisonous and is harmless when touched, however, caution must be taken when in close proximity to avoid accidentally allowing the invasion to spread.

Young Japanese knotweed shots are in fact edible, providing a fantastic source of vitamin A. It can be used in sauces, soups and desserts, offering a taste likened to rhubarb.

Read more: What Eats Japanese Knotweed?

As a result of Japanese knotweed’s ability to rapidly spread and cause a lot of problems, properties and homes affected by the invasive plant do run the risk of their value being impacted. Blocked drains and damage to foundations, walls and paths can all occur as a result of Japanese knotweed.

To prevent the spreading of Japanese knotweed, it is important that when discovered not to attempt to break or move stems or uproot the plant. Japanese knotweed spreads though fragments of cut stems and rhizomes which are capable of creating new shoots and roots when buried in soil. These fragments can be carried completely unnoticed; therefore, caution must be taken when dealing with Japanese knotweed.

To remove Japanese knotweed, it is advised that trained and qualified specialists be called in to deal with any recognised infestation as the risk of the weed spreading is very high when not dealt with correctly.

Many herbicides, when applied correctly, have the ability to kill Japanese knotweed also. For the best results, apply over several years.