Team tackles invasive river weed

The weed has to be destroyed by hand or machinery

Work has begun to clear a highly invasive foreign water weed from the River Tone in Somerset.

Floating pennywort grows at about 20cms (5ins) a day, forming dense mats that smother native plants and can cause the river to flood.

The Environment Agency said there has been a new outbreak of growth between Ham and Newbridge Sluice.

The weed has to be removed and destroyed either by hand or machinery to prevent it spreading downstream.

Floating pennywort (Hydrocotyle ranunculoides) is native to North America.

'Cause havoc'

It was brought to Britain in the 1980's as a decorative plant for ponds and aquaria.

John Rowlands, who is leading the work, said: "We never established the source of the outbreak last year and spent a great deal of time removing it, so it is frustrating to see it return.

"Problems caused by floating pennywort include the ousting of native vegetation, de-oxygenation (which kills fish) and an increase in the flood risk from blocked channels and, during high flows, the mats being washed into pumping stations.

'We are lucky that it has been discovered before higher winter river flows have a chance to carry it downstream where it could cause havoc throughout the river system.'