One favorite at the moment is butterbur, also called Petasites hybridus.    From Wordnik.com.  [Companies Cashing In On Allergies] Reference

Rare species in northern Kazakhstan are: Ledum palustre, Oxycoccus palustris, Petasites frigidus, Eriophorum vaginatum, and E. gracile.    From Wordnik.com.  [Kazakh forest steppe] Reference

Also found in wetland areas are wet graminoid herbaceous communities, dominated by sedges (e.g Eriophorum anjustifolium and Carex spp.) or codominated by sedges and herbs (e.g. Menyanthes trifoliata, Petasites frigidus, and Potentilla palustris).    From Wordnik.com.  [Copper Plateau taiga] Reference

Petasites; in the second, Carduus tomentosus and Picris Echioides.    From Wordnik.com.  [Proserpina, Volume 2 Studies Of Wayside Flowers] Reference

This plant (Petasites hybridus), native to Europe, northern Africa and southwestern Asia has been clinically studied.    From Wordnik.com.  [The Full Feed from HuffingtonPost.com] Reference

One of the most powerful and clinically proven herbs used to prevent and treat headaches and migraines is Butterbur (Petasites hybridus).    From Wordnik.com.  [MyLinkVault Newest Links] Reference

(wall pennywort), and the Tussilago Petasites (butter-bur), Stellaria.    From Wordnik.com.  [Records of Woodhall Spa and Neighbourhood Historical, Anecdotal, Physiographical, and Archaeological, with Other Matter] Reference

A close-up shot of the flowers of butterbur (Petasites hybridus.    From Wordnik.com.  [The Magpie's Hoard] Reference

Petasites vulgaris, Saxifraga Burseriana.    From Wordnik.com.  [Hardy Perennials and Old Fashioned Flowers Describing the Most Desirable Plants, for Borders, Rockeries, and Shrubberies.] Reference

Petasites vulgaris, 198.    From Wordnik.com.  [Hardy Perennials and Old Fashioned Flowers Describing the Most Desirable Plants, for Borders, Rockeries, and Shrubberies.] Reference

(or Bog Rhubarb; Petasites hybridus) tract.    From Wordnik.com.  [Recently Uploaded Slideshows] Reference

Petasites 518.    From Wordnik.com.  [Catalogus bibliothecæ historico-naturalis Josephi Banks ... Auctore Jona Dryander, ...] Reference

Tussilage Petasites.    From Wordnik.com.  [Catalogus bibliothecæ historico-naturalis Josephi Banks ... Auctore Jona Dryander, ...] Reference

Chrysanthemum, Lilium auratum, Origanum pulchellum, Petasites vulgaris.    From Wordnik.com.  [Hardy Perennials and Old Fashioned Flowers Describing the Most Desirable Plants, for Borders, Rockeries, and Shrubberies.] Reference

Aralia Sieboldi, Eranthis hyemalis, Helleborus foetidus, H. niger, H. orientalis, H. olympicus, Jasminum nudiflorum, Petasites vulgaris.    From Wordnik.com.  [Hardy Perennials and Old Fashioned Flowers Describing the Most Desirable Plants, for Borders, Rockeries, and Shrubberies.] Reference

Imperati, G. nivalis, G. plicatus, Helleborus abchasicus, H. antiquorum, H, Bocconi, H. colchicus, H. cupreus, H. dumetorum, H. foetidus, H. guttatus, H. niger, H. odorus, H. orientalis, H. olympicus, H. purpurascens, Hepatica angulosa, H. triloba, Jasminum nudiflorum, Petasites vulgaris, Polyanthus, Primula acaulis, Saxifraga Burseriana.    From Wordnik.com.  [Hardy Perennials and Old Fashioned Flowers Describing the Most Desirable Plants, for Borders, Rockeries, and Shrubberies.] Reference