NON-NATIVE INVASIVE SPECIES – THE JAPANESE KNOTWEED

The Japanese Knotweed 

The Japanese Knotweed in one of the most invasive non-native plant species to have been introduced into this country. With its natural habitat being on the slopes of volcanoes, it is no surprise that the less harsh and more fertile environment of Britain has allowed this plant to flourish to extreme proportions. Furthermore, outside of Asia, the plant has no natural biological enemies to check its spread. In Japan, for example, there are at least 30 species of insect and 6 species of fungi that live off this plant.

Non-native species - The Japanese Knotweed 

It thrives on disturbance. The tiniest piece can re-grow enabling the plant spread across the country by both natural means and human activity. Once established, it can quickly overrun riverbanks, railway embankments, road verges, gardens and hedgerows. This rapid growth and speed of travel makes the Japanese knotweed a severe threat to the survival of native plant species, insects and therefore other native animal species.

Introduced to Britain between 1825 and 1841 the Japanese knotweed is now recognized as the most invasive and damaging weed in the country, even able to force its way through cracks in walls and pavements. It can grow to 13 ft in height and with no natural pests or diseases – combined with a strong resistance to commercial weed killers - it has proved to be almost impossible to control.

Huge sums are being spent in the UK controlling the weed. In 2004, a DEFRA review of non-native species policy stated that a conservative estimate for the costs involved in eradication would be approximately £1.56 billion. The aggressive spread of the plant has now resulted in it being listed in the Wildlife and Countryside Act 1981 as a pest species. All parts of the plant are considered as controlled waste under the Waste Regulations.

For related articles click onto the following links:
NON-NATIVE INVASIVE SPECIES – THE CHINESE MITTEN CRAB
RHS: Japanese knotweed

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