Butterbur

Wild Rhubarb, also known as butterbur (Petasites vulgaris)
However the more prolific name of butterbur recalls the use of its leaves to wrap pats of butter. It is also known as "Sons before Fathers" in reference to its habit of producing flowers before leaves. 

The plant is also imbued with a range of traditional medical uses from a cure for plague and leprosy to more common place colds and bronchial complaints. In modern medicine an application for the active chemical petasine has been supported in a number of clinical trials. It is used in migraine control medication and applications in other fields are being explored.

Information courtesy of - http://www.geograph.org.uk/photo/1348285