A GARDENER from north Essex is worried a menace weed known as "the alien invader" is putting native wildflowers at risk.Sheila Sansom contacted the Environment Agency and Colchester Borough Council after she spotted three large clumps of Japanese knotweed growing along the banks of the River Colne.

By Juliette Maxam

A GARDENER from north Essex is worried a menace weed known as "the alien invader" is putting native wildflowers at risk.

Sheila Sansom contacted the Environment Agency and Colchester Borough Council after she spotted three large clumps of Japanese knotweed growing along the banks of the River Colne.

The triffid-like weed, which can grow at the rate of two centimetres a day, has spread to land near the river, including her next-door neighbour's garden in Causton Road and an alleyway nearby.

Japanese knotweed was introduced to Britain in the 19th century, but gardeners became disillusioned with as it grew so quickly smothering native plants.

The weed can reproduce from a fragment of root as small as 0.8 grams forming dense clumps which can grow to three metres high. The vigorous weed can even grow through tarmac or the floors of houses causing damage to property.

It increases the risk of riverbank erosion when the dense growth of the plant dies back in the autumn exposing bare soil. It can also create a flooding hazard if the dead stems are washed into streams and clog up channels.

Under the Wildlife and Countryside Act, it is an offence to plant or encourage the growth of Japanese knotweed, which could include cutting the plant or roots and disturbing surrounding soil.

Developers removing knotweed from building sites have to treat is as "controlled waste" and it is regarded as a pollutant.

Mrs Sansom said: "In Devon they call it the alien invader and if anybody sees it they have to report it. It grows so quickly and spreads under the ground. It can do away with all of our own wild flowers."

She added: "I think if we leave it it's going to destroy all our natural flowers, the rate it grows and the height it grows. Only a little bit needs to be carried along the water and then if it settles it grows into another clump."

"I've written to the Environment Agency and spoken to several people from them and I've spoken to Colchester Borough Council but nobody seems very concerned."

A spokeswoman from the Environment Agency said there are guidelines for people with Japanese knotweed on their land which can be seen on the organisation's website, www.environment-agency.gov.uk or can be obtained on a leaflet by telephoning 08708 506506.

A Colchester Borough Council spokesman said the council would only become involved in trying to eradicate Japanese knotweed if it was growing on council land.

Yesterday there was some confusion about who owns the riverbank where knotweed is growing.