Hydrocleys nymphoides (Alismataceae) naturalised in New South Wales waterways

Abstract

Hydrocleys nymphoides (Humb. & Bonpl. ex Willd.) Buchenau (Alismataceae) is a stoloniferous emergent/floating perennial aquatic plant native to the Neotropics. In Australia it is naturalised in Queensland, New South Wales, Victoria and the territory Norfolk Island. The earliest non-cultivated collection in New South Wales was made in November 1957 from Castle Hill in Sydney, and although it involved an infestation in several farm dams it was not considered an established naturalised species in that state. Since then it was reported occurring in a dam at Murwillumbah in 1993 and from 2009 naturalised records have been collected from the Murray River at South Albury, near Coffs Harbour on the north coast, and on the Hacking River at Audley in the Royal National Park, south of Sydney. H. nymphoides, commonly called Water Poppy, is grown as an ornamental and has the potential to escape further as an invasive weed, particularly in disturbed wetlands and waterways. A description with images of H. nymphoides, and notes on distribution and genome size are provided.