| Noun | 1. | giant willowherb - tall North American perennial with creeping rootstocks and narrow leaves and spikes of pinkish-purple flowers occurring in great abundance in burned-over areas or recent clearings; an important honey plantEpilobium, genus Epilobium - large widely distributed genus of herbs and subshrubs of especially western North America and Arctic areas willowherb - a plant of the genus Epilobium having pink or yellow flowers and seeds with silky hairs | |