Fallopia Japonica

Fallopia Japonica commonly known as Japanese Knotweed, other names include elephant ears, Japanese bamboo, American bamboo or Mexican bamboo and it is rated among the 100 worst invasive species in the world by the Global Invasive Species Programme (GISP)

It is a large herbaceous woody perennial, it has hollow stems with distinct raised nodes that give it the appearance of bamboo, though it is not closely related.

This fast growing perennial can reach 2 to 3 metres in height during the summer. Its hollow, gnarled stems are similar to those of bamboo, thus the descriptions of Japanese bamboo, or Mexican Bamboo are sometimes attributed to it.

The leaves are heart shaped, with a flat bottomed edge and a lush green colour, in summer it produces an abundance of cream white flowers and at first glance these striking blooms are enough to win over any gardener- but do not be deceived, this beautiful plant Japanese Knotweed is rated among the 100 worst invasive species in the world by the Global Invasive Species Programme (GISP).

Closely related species include Giant Knotweed Himalayan Knotweed and Bohemian Knotweed – Invasive Species

Fallopia Japonica is native to Japan and Northern China.  Fallopia Japonica was originally introduced to both the UK and Ireland by the late Victorians as an ornamental for their gardens but quickly escaped into the wild.

The plant is now widespread across both islands particularly on roadsides, hedgerows, railways, waste-ground, riverbank and wetland habitats.  The invasiveness of the plant is a result of its hardiness and the speed at which it can grow, it quickly forms tall stands shading out the areas below and excluding all other vegetation.

Native plants can rarely compete with this invasive species and local plant biodiversity is reduced.  This invader is very persistent and once it becomes established, is incredibly difficult to control.

Fallopia Japonica is a rhizomatous perennial plant with distinctive branching, hollow bamboo like stems covered in purple speckles, the plant can reach 2-3 meters high in full growth.

The leaves are heart shape and a lush green colour and are arranged on arching stems in a zig zag pattern. Fallopia Japonica flowers late in the summer season with creamy white flowers hanging in clusters.

The underground rhizomes are thick and woody with a knotty appearance and when broken can reveal a bright orange-coloured centre, this root system can extend to and beyond a depth of at least 2m and extend 7m laterally from a parent plant.

During winter the leaves of Fallopia Japonica die back to reveal the bamboo type canes that will turn darkish red / brown and die, the canes can remain standing for several years.

In spring the plant sends up new shoots, red/purple in colour with rolled back leaves, these shoots grow rapidly due to stored nutrients in the extensive rhizome system.  Growth rates of up to 40mm a day have been recorded.

Only female Fallopia Japonica plants have been recorded to date in Ireland and the UK therefore it is spread entirely from site to site through the deliberated or accidental movement of rhizome fragments or cut stems.

Fallopia Japonica thrives on disturbance and accordingly invades rural and urban environments where soils are routinely disturbed and transported.

In rural areas, the problems include disrupting sight lines on roads and railways and in the riverside environment disrupting flood defence structures.

The plant damages the urban environment by pushing up through tarmac and paving, by out-competing other species in planting programmes as part of landscaping schemes and causing aesthetic problems as litter accumulates in the dense thickets formed by the plant, this can attract vermin.


Fallopia Japonica has been removed from the natural enemies that control it in its native range in Japan. It out- competes our native animals and plants.

The spread of Fallopia Japonica is a serious threat to our countryside and the native animals and plants that rely upon it.


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