Petasites japonicus, also known as Fuki, bog rhubarb, or giant butterbur, is an herbaceous perennial plant in the family Asteraceae. It is native to Japan, where the spring growth is relished as a vegetable. It has also been introduced to southern British Columbia by Japanese immigrants.
The traditional preparation method for this vegetable involves pre-treating with ash or baking soda and soaking in water to remove harshness, which is a technique known as Aku-nuki. A new phenolic compound, petasiphenone, was isolated from the dried rhizomes ofPetasites japonicus together with the known phenolic compound, peta.

Like other Petasites species, fuki contains pyrrolizidine alkaloids which have been associated with cumulative damage to the liver and tumor formation. The concentration of potentially hepatotoxic pyrrolizidine alkaloids are below the detection limits in modern butterbur extracts.