This perennial grows from deep rhizomes. The leaves are large, suborbicular and up to 20 cm across and stalked with small regular teeth. The species is dioecious, male and female flowers being borne on separate plants. The erect flower-heads grow in short racemes on stems up to 25 cm long with a few scale-leaves. The florets are pinkish-mauve and appear in December in Ireland and from January to March:323 in Great Britain. The flowers have a vanilla-like scent. Other species to be found in Ireland and Great Britain: Petasites hybridus (L.) P.Gaertner, B. Meyer & Scherb, Petasites albus (L.) Gaertner. and Petasites japonicus (Siebold & Zucc.) Maxim.
Petasites pyrenaicus is native to the Mediterranean region of Europe, including Italy, Sicily, Sardinia and north Africa. It was introduced to Great Britain in 1806 where it has become naturalized. It was recorded in the wild by at least 1835 in Middlesex  It is also introduced and naturalized in Ireland. Female plants are unknown in the British Isles.:771 The male plant is grown as an ornamental in gardens and some churchyards, and was well established by the start of the 20th century.
Common on shady roadside banks. The underground rhizomes allow it to spread and its large leaves can shade out other plants. It is considered an invasive plant but can be controlled by cultivation or weedkiller.
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- Stace, Clive (2019). New Flora of the British Isles (4th ed.). C&M Floristics. ISBN 9781527226302.
- W. Keble Martin 1965. The Concise British Flora in Colour. Ebury Press and Michael Joseph
- Parnell, J. and Curtis, T. 2012. Webb's An Irish Flora. Cork University Press. ISBN 978-185918-4783
- Clapham, A.R., Tutin, T.G. and Warburg E.F. 1968. Excursion Flora of the British Isles. Cambridge University Press. ISBN 0 521 04656 4
- Stace, C. A. (2010). New Flora of the British Isles (Third ed.). Cambridge, U.K.: Cambridge University Press. ISBN 9780521707725.
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- Hackney,1992. Stewart & Corry's Flora of the North-east of Ireland. Institute of Irish Studies and Queen's University of Belfast. ISBN 0 85389 446 9
- "Butterbur and winter heliotrope". The Royal Horticultural Society. Royal Horticultural Society. Retrieved 15 December 2019.