Through the summer and autumn of 2010, Louise Hill and other members of the Doncaster Naturalists’ Society have been monitoring the progress of the newly arrived and highly invasive American Floating Pennywort Hydrocotyle ranunculoides in the River Don and South Yorkshire Navigation in the Doncaster region. Substantial populations are currently present at Sprotbrough Locks, the course of the old River Cheswold at Crimpsall and in the Canal basin opposite St George’s Minster in central Doncaster (see Figure below). Smaller populations have been noted on the Don at Sprotbrough Falls, Church Rein, Hexthorpe (opposite the allotment dog-leg), Crimpsall Rock Chute and in the canal at Strawberry Island and Long Sandall.
In addition to these sites, Geoffrey Wilmore (YNU Alien Plants recorder) knew of the plant in South Yorkshire back in 2000 when Jeff Lunn reported it the Barnsley Canal at Wilthorpe. In West Yorkshire Geoffrey Wilmore and Jill Lucas monitored its appearance in a small brook in Huddersfield in 2005, and its colonisation of the Calder and Hebble Navigation notably the ‘Figure of Three’ Locks at Horbury and riverside flashes in the Ossett and Horbury areas.
During 2010 the Environment Agency has employed a contractor to spray with herbicide any Floating Pennywort colonies found from the Rother all the way down the Don and South Yorkshire Navigation to Crimpsall (Doncaster prison) (twice). Over the next few weeks the EA is also surveying the Rother (by canoe!) all the way up to Chesterfield to try to find the source of the infestation. In addition, the EA is also dealing with it on the Aire and Calder Navigation at Castleford.
The Environment Agency with various partner organisations including British Waterways, Doncaster and Wakefield Councils and the Don Rivers Trust and the Colne & Calder Rivers Trust has formed the ‘Yorkshire Pennywort Forum’. Its aims are to provide a co-ordinated response to this invasive weed, to record and monitor its spread in Yorkshire and to tackle it in key areas.
In 2010 British Waterways allocated £20K for Pennywort control, and a further £10K is coming from the Flood Risk Management team at the Environment Agency. As a result in 2010 it has targeted pennywort control on the Rivers Don, Rother and Calder.
A useful website on American Floating Pennywort in the UK is:
Louise Hill & Colin Howes (Doncaster Naturalists’ Society)