Gardeners who have grown members of this genus knowingly refer to it as "pestasites" because the plants easily become invasive. In some situations, however, they have a lot to offer. One of the biggest perennials for the hardy garden is P. japonicus 'Variegatus' (also called P. japonicus giganteus 'Nishiki-buki'). This plant produces great rounded leaves to 4ft across, each splashed and streaked with yellow. Flowers appear early in spring before the leaves. The plants love moisture and their big, rough-and-tumble look makes them perfect for the edge of a stream or pond or in a boggy area. Monet had a stand at the edge of his famous Wisteria bridge.
Google images http://twurl.nl/xsoevj http://www.stauder.net/bildearkiv/Petasites japonicus bladverk 3.jpg