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Invasive plant with potential to ‘carpet rivers’ found in Norfolk Broads

PUBLISHED: 12:50 06 October 2020 | UPDATED: 17:35 06 October 2020

Floating pennywort has been spotted in the River Ant. Photo: NNNSI

Floating pennywort has been spotted in the River Ant. Photo: NNNSI

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People have been warned not to “dump” plants in rivers after an invasive species was found floating in a Broads waterway.

Floating Pennywort has the potential to 'carpet rivers'. Photo: Steven PullingerFloating Pennywort has the potential to 'carpet rivers'. Photo: Steven Pullinger

According to the Broads Authority, the rogue floating pennywort has been spotted in the upper reaches of the River Ant - and has the potential to “carpet” rivers entirely.

In a Facebook post, the authority said: “We are concerned that the invasive floating pennywort has been spotted. This plant can carpet rivers and increases management costs for navigation authorities who have to clear it up.

“We are working with partners at the Environment Agency, and North Walsham and Dilham Canal Trust to investigate the latest outbreak.

“It looks likely to be a result of someone dumping plants from their pond into the natural waterway.”

A volunteer removing floating pennywort from one of the rivers of the broads.  Photo: Steve Pullinger.A volunteer removing floating pennywort from one of the rivers of the broads. Photo: Steve Pullinger.

It said: “Please, if cleaning out your pond, make sure you compost the plants and never dump them.

“Be plant-wise, and learn how to spot this invader and report it to the Norfolk Non-Native Species Initiative (NNNSI).”

On its webiste the NNNSI noted that the floating pennywort, originally from North America, was “spreading rapidly” across the UK, and was “proving to be particularly invasive in Norfolk”.

It also said that operations were underway to “eradicate the species” from the River Waveney.

Since 2014, the pennywort has been banned from sale and is illegal to plant in the wild.

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The rapid growth of the plant can lead to the formation of dense patches - which can be mistaken for solid ground.

The NNNSI’s website says: “This can easily become a problem for us, dogs and other animals which can fall and potentially become trapped.

“These dense mats often push out native plants and clog waterways. In Britain, an estimation of the costs of chemical control for this species can be up to £300,000 per year.”

Other notorious non-native and invasive species include the Japanese knotweed and giant hogweed.

In April 2020, the Environment Agency labelled Japanese knotweed as “indisputably the UK’s most aggressive, destructive and invasive plant”.

However, while this invasive plant tends to affect urban areas, and can cause damage to buildings by targeting weak points in bricks and pipes, the recent outbreak of pennywort is very much a water-centric issue.

NNNSI ask that if anyone sees a suspected case of pennywort they should take a photo, record the date and location, and email NNNSI@norfolk.gov.uk


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