1) Bog rhubarb 2) Found in moist areas 3) Herb 4) Herbaceous plant 5) Petasites hybridus 6) Petasites vulgaris 
• (n.) A broad-leaved plant (Petasites vulgaris) of the Composite family, said to have been used in England for wrapping up pats of butter.
But'ter·bur` noun (Botany) A broad-leaved plant ( Petasites vulgaris ) of the Composite family, said to have been used in England for wrapping up pats of butter. 
Butterbur: A waterside plant with purple flowers and large soft leaves in which pats of butter were once wrapped during hot weather in England. The rhizome (root) of butterbur has been used as an herbal remedy for fever, asthma, colds, and urinary complaints and was also thought to be a cardiac 'tonic' and a diuretic. Butterbur holds some promise a...
[n] - small Eurasian herb having broad leaves and lilac-pink rayless flowers
bog rhubarb noun small Eurasian herb having broad leaves and lilac-pink rayless flowers; found in moist areas
any of several composite plants of the genus Petasites, having large, woolly leaves said to have been used to wrap butter.