Japanese knotweed: an ecological disaster that must be banned from your garden!

Plant identification card
Botanical name Japanese reynoutria, Fallopia japonica.
A common name Japanese knotweed, pointed knotweed.
Family Polygonaceae.
Origin east asia.
Dimensions Its maximum height is 4 meters, reached in spring in just two months.
Leaves Its leaves are oval or triangular, alternate, forming zigzags. The formation of leaves takes place continuously from spring to summer and they fall from November.
Bloom Late (September-October) and manifested by numerous small white flowers, producing nectar and honey, installed in panicles in the axils of the leaves.
Fruiting It is a 2 to 4 mm long achene that is not very fertile. It is therefore not responsible for the propagation of the plant.
Exposure Sunny to partial shade.
Ground floor It grows in poor, toxic or unstable soils, although it likes moist and rich soils.
Rusticity The very robust Japanese knotweed can withstand temperatures as low as -25°C.

First introduced to Europe in the Middle Ages for its foraging properties, Japanese knotweed became invasive in the 20th century due to industrial development.

What are the characteristics Reynoutria japonica ?

Japanese knotweed is a perennial herb that has hollow, upright, reddish stems resembling bamboo sticks. These stems come from an impressive rhizome about a foot in diameter.

The Japanese Kestrel is geophytic plant, that is, its aerial stems die back in winter, but the underground buds persist. They develop close to the surface to give rise to new shoots in the spring.

Japanese knotweed is a perennial herb that has hollow, upright, reddish stems resembling bamboo sticks.

Japanese Knotweed settles on its own in a degraded environment such as urban wastelands, railway lines, illegal dumps or around polluted streams and rivers. It doesn’t run into competition there, and for good reason! Produces aromatic chemical compounds toxic to the roots of other plants.

Vegetative reproduction of the Japanese knotweed does not take place by its seeds, but by means of it its rhizomes that spread, constantly produces new shoots. Note: a rhizome or stem fragment the size of a marble can regenerate a clump after 10 years of latency!

What kind of soils does Japanese Knotweed inhabit?

Unlike most plants, he likes Japanese knotweed depleted soil. It is actually a bioindicator of soils polluted by heavy metals and aluminum, which they value very much. It was also the first plant to colonize metal-rich lava flows. Its name comes from the location of the first industrial sites attacked by the plant, which were located in Japan.

Japanese knotweed is a bioindicator plant for soils polluted by heavy metals and aluminum.

How to get rid of Japanese knotweed?

Of course, Japanese knotweed is not a welcome plant in the garden! If you are unlucky enough to have him move into your home, that is urgent to disappear ! How ? Start by extracting the rhizomes and then install black plastic sheeting. Mow as the regrowth progresses to exhaust the plant until it is completely gone.

The tarpaulin will prevent possible stem or rhizome fragments from settling. To facilitate its elimination, install fast-growing shrubs such as hazel, black elder or willow at the site of the invasion. You can also opt for climbing plants with strong covering ability. Be alert to harvest new spontaneous clumps from your garden as soon as possible.

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