Extracted from January 2018 Newsletter
It may sound like the scary clown in a Stephen King book, but in fact Pennywort is an invasive weed. And its threatening to colonise St. Patrick’s Stream.
Apparently, ‘Pennywort’ is a commonly used term and is applied to several different plant species. The strain that causes problems, and is present on the Pats, is Floating Pennywort (Hydrocotyle ranunculoides).
Not only is it non-native and considered invasive, the threat it poses resulted in it being banned from sale in April 2014. In fact, under the schedule 9 of the Wildlife and Countryside Act, in England and Wales, it is an offence to plant or otherwise cause to grow the plant in the wild.
The weed forms thick floating blankets of round leaves and in ideal conditions is thought to grow as much as 20 cm a day, impacting levels of oxygen in the water. As a result, it is a direct threat to fish and invertebrates as well as native water flowers.
Removing Floating Pennywort is challenging, not least because it is able to re-grow from even a small fragment. Several patches have been identified on the Pats and are thought to have resulted from work by the EA to remove the weed on the Thames.
To address the threat, specialist contractors were hired at the end of last year to remove the weed.