Difficult to be very precise on this one, since we walked about 20 km through the Wutachschlucht, and I didn't have a GPS at the time. Still, it's probably roughly the right area.
Gewöhnliche Pestwurz (Petasites hybridus) am Staden in Saarbrücken
Photos are by my older sister.
The plants commonly referred to as Butterbur are found in the daisy family Asteraceae in the genus Petasites. They are mostly quite robust plants with thick, creeping underground rhizomes and large Rhubarb-like leaves during the growing season. Another common name for many species of this genus is Sweet Coltsfoot.