Petasites japonicus

In May, when the growing season is just beginning and the ground may look a little bare, bog rhubarb puts up round, yellow-green flowers. Like coltsfoot (Tussilago farfara), the flowers precede the leaves, only the scale is quite different. When bog rhubarb has finished flowering, the ground is covered with huge, lightly-toothed, kidney-shaped leaves on thick stalks. The Japanese have also eaten this rhubarb. Recent research has, however, discovered harmful and even dangerous substances in bog rhubarb, thus internal use is not recommended.