Be aware of the japanese knotweed tree

May 30, 2019
japanese knotweed

It is a perennial herbaceous plant with hollow, bamboo-like stems that can exceed 3 meters in height and large, heart-shaped leaves more than 15 cm long. It is the nightmare for every gardener as it is very hard to prevent it form spreading. Click here for japanese knotweed.

Chronicle of an invasion

Native to Asia, this plant was introduced in Europe in the middle of the 19th century by gardeners passionate about novelty and exoticism. This beautiful ornamental has progressively acclimatized and then dispersed on the continent. The many development works in the middle of the 20th century accelerated its spread via land transport, machinery and the disruption of natural environments. Visit this site for japanese knotweed.

In Auvergne, it was described for the first time in the department of Allier since 1930 and in the department of Puy-de-Dôme in 1956. She experienced a real explosion along the rivers and roads in the 1980s. Today it is an invasive plant among the most problematic in Auvergne and Livradois-Forez.


It is concentrated mainly along rivers, roads and agglomerations. It is implanted on all the areas remodeled by the man, whatever the altitude, or the nature of the ground.

A formidable efficiency

This plant species is one of the most productive of the temperate flora. A fragment of aerial stem or rhizome is enough to give back a plant that can live more than 10 years. In the absence of local predators, and diseases, the knotweed is a formidable competitor who eliminates other plants by secretion of chemical substances (allelopathic power such as Walnut). It has a powerful root system with rhizomes that grow up to 3 meters deep exceeding 10 meters in length, and that allow it to resist chemical or mechanical control techniques.

knotweed and menjapanese knotweed

In its zone of origin this plant is not invasive. But in our country, by its spectacular development, the Knotty raises problems. It’s mowing and grinding are particularly effective factors of propagation by cuttings. The development works contribute greatly to its dissemination. Its highly developed but particularly brittle root system does not stabilize the banks of rivers that erode at the slightest flood by driving pieces of Renouée downstream and thus promoting the establishment of new homes.

In the wild, its location is often detrimental to native plants and natural environments and contributes to the loss of biodiversity.

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