Troublesome floating pennywort

Floating pennywort is a very invasive floating water plant, which can overrun water systems within a few years. Canals are particularly susceptible, as the plant grows quickly in the slow moving, nutrient rich, warm water.

Floating pennywort is a native of North America. It was bought to Britain in the 1980’s by garden centres, to be used in garden ponds. The plants can form dense, interwoven mats, which can cover the water surface very quickly. In one site in the UK, it was noted that the plant spread by 15 metres, in one growing season.

If the plant takes hold it can cost £10,000's to remove and dispose of.  It will completely dominate an area, so that nothing else can survive (as it blocks out sunlight and oxygen).  The Trust is very aware of the invasive nature of the plant and if we are told about the plant being present on our canals, we ensure it is removed as quickly as possible.  

No sneaky patches

Towards the end of last year, two small patches of floating pennywort were noted on the offside of the Worcester and Birmingham canal, which we removed. The plant has occurred on this stretch before, so we wanted to be sure that there were no sneaky patches hiding in the marginal plants or overwintering on the offside. 

So a few days ago our intrepid ecologist, Stuart and willing volunteer, Ian, took a boat up the northern half of the Worcester and Birmingham to hunt through the undergrowth. I am pleased to say that nothing was found, but we will continue to undertake spot checks. 

If you do see anything that look that looks like floating pennywort, please report it us, by email: or by phone: 0303 040 4040.

Last date edited: 14 May 2015

About this blog

Sara has been with the Trust for 17 years, working in the environment team. She is a senior environmental scientist and will cover waste and water quality issues. She works closely with the South Wales and Severn Waterway team but her work will also pick up national issues, such as the Water Framework Directive.


See more blogs from this author