All Petasites (and Tussilago) species contain livertoxic pyrrolizidine alkaloids. Don't use them. More info here: Livertoxic PAs --Henriette
Names. Boreal Coltsfoot.
Fr. Tussilage glaciale.
Classif. Nat. Order of Corymbiferous. Syngenesia superflua L.
Genus TUSSILAGO. Perianthe simple, equal, multipartite, membranaceous, swelled below. Phoranthe naked. Pappus simple sessile. Many narrow female rays.
Sp. Tussilago frigida. L. Radical leaves on long petioles, cordate, unequally toothed, woolly beneath. Scapes multiflore, thyrsus oblong fastigiate bracteate, flowers radiate.
Description. Root perennial. Leaves all radical, petioles long, thick, canaliculate; leaves cordate rounded or subdeltoid, nearly obtuse, many unequal teeth, green and rugose above, woolly and white beneath. Scape longer than the leaves, terete and thick, 9 to 12 inches high, with some remote lanceolate acute scales; many flowers, forming a thyrsus or oblong raceme, peduncles shorter than the flowers, axillary to subulate bracts, rays white, disk purple.
History. A genus with many anomalies, often polygamous or dioical, with evident or obsolete rays, whence the subgenera 1. Farfara, flowers radiate. 2. Petasites, flowers discoidal. 3. Anandria, dioical. This species is a native of the boreal regions of the three continents, Europe, Asia, and America, in the mountains of Lapland, Norway, Siberia, Canada, Maine, Labrador, Greenland, &c. It blossoms in June. We have also in America the common Coltsfoot or T. farfara of Europe, found in New England, New York, Ohio, &c. It blossoms in April, before the leaves spring up: easily known by its yellow radiate flowers, scapes uniflore and scaly, leaves cordate, angular. Both species will be included here, having similar medical qualities. Tussilago, derives from Tussis or Cough, as useful for it.
Properties. The whole plants are used, but and leaves; their smell and taste are somewhat pleasant, aromatic, bitterish, austere, and mucinous. They contain mucilage, extractive, tannin, &c. They are reckoned demulcent, restringent, cephalic, errhine, pectoral, diaphoretic, deobstruent, &c. Often used in Europe and America for coughs, complaints of the breast and lungs, asthmatic affections, hooping cough, and also in scrofula: either in tea or decoction, conserve or powder. A small pinch of the powdered leaves is a very mild errhine, and a good cephalic, removing diseases of the head, giddiness, obstructions in the nose, headache, &c. It is the base of the "herb-tobacco", used for that purpose in New England. Our medical writers have neglected the Coltsfoot, or spoken of it as nearly inert, but it is a mistake; Cutler and Henry alone mention it as useful; the Shakers and herbalists use it beneficially. Their powers in diseases of the breast are not strong, but available for consumptive coughs and hooping cough, in warm infusion, sweetened with honey, or boiled in milk. A strong decoction has cured scrofula (along with Nymphea, as a poultice, over the swellings of the neck) half a pint of the decoction was taken three times a day.
Medical Flora, or Manual of the Medical Botany of the United States of North America, Vol. 2, 1830, was written by C. S. Rafinesque.