This species was introduced to the UK as an ornamental pond plant, but has proven to be incredibly invasive and left unchecked can block whole waterways and overwhelm native flora. It spreads mainly by plant fragmentation but also by seed and has caused significant environmental problems across Europe; it is now on the UK’s most-wanted list but fortunately it is still confined to a relatively few areas, making early eradication still feasible. It is easiest to spot in late summer when it produces bright yellow flowers floating on ponds; it can though be confused with other less invasive species and so identification by an expert may be necessary to confirm an outbreak. One way of removing it is by diving down to pull out the roots from the bottom of ponds and lakes, but this is a method probably best left to the professionals!
Photo Credit GBNNSS