Questions and Answers

Japanese Knotweed took 100 years to become an invasive weed of any note in these islands.

Floating Pennywort, Hydrocotyle ranunculoides, since first reported naturalised in 1991, is already doing serious environmental damage and hampering water management in many sites in southern England.

Sharing with Japanese Knotweed the ability to reproduce itself from the tiniest plant fragment and thereafter to grow with alarming rapidity, it is likely that further spreading will occur at a substantial speed. In 1999, there were only 35 reports of infestations, mainly in the southern counties of England and Wales. The number of sites by 2003 had increased to more than 90, and there is no reason to suppose that such a rate of increase is not continuing.

Floating Pennywort is a native of North America.

It has spread to Central and South America, where it may be considered as indigenous, and to Australia, where it has become a serious nuisance.

Introduction here was in the 1980s through the nursery trade for water garden planting, sometimes erroneously sold as the native Marsh Pennywort, Hydrocotyle vulgaris.

From this April, Floating Pennywort has been classified under Schedule 9, section 14 of the Wildlife and Countryside Act, which makes it illegal to plant or cause it to grow in the wild.

Only time will tell how effective is the legislation and how resilient Floating Pennywort.

YP MAG 22/5/10