Invasive species: There are a number of non-native plant and animal species which are considered to be potentially invasive, although some may not yet have shown indications of being invasive on the Isle of Man. Montbretia (Crocosmia) covers some of the coastal slopes. Winter heliotrope Petasites fragrans is found by roads and rivers. Himalayan balsam Impatiens glandulifera and giant hogweed Heracleum mantegazzianum occur by rivers. Coarse fish are moving between ponds with the help of man, while some species such as Japanese knotweed Fallopia japonica and Sargassum muticum seaweed are spreading of their own accord.