This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Unlike its near neighbour Coltsfoot, Butterbur is not found in early deposits. It is found in the North Temperate Zone to-day in Europe, North Africa, N. and W. Asia. It is found in every part also of Great Britain except the Isle of Wight, Glamorgan, West Sutherland, as far north as the Shetlands; but it is local, and ascends to 1000 ft. in Northumberland; and in Ireland it is also native.
Butterbur is a paludal species, which grows in very similar places to Coltsfoot. It, however, frequents the near neighbourhood of water more consistently than the latter, and is found on the borders of rivers, streams, and lakes, forming dense brakes with its huge rhubarb-like leaves.
Like Coltsfoot the Butterbur is soboliferous, with creeping underground stems. The stems are woolly scapes. The leaves1 are flat, large, kidney-shaped or heart-shaped, toothed along the margin, smooth, reddish, covered with a felt at the base, downy beneath, and very large. The leaf-stalks are long, round, finely-furrowed, sheathed below, channelled, and purple. They are usually softly and loosely hairy.
1 Perfectly adapted to a habitat where moisture is abundant, water copiously supplied, and the shade considerable.
The plant is dioecious, with male florets and female on different plants, the male florets being rarest, and in a dense egg-shaped panicle, the female ones loose and longer, the styles of the first being egg-shaped and stout, the female with the mouth obliquely blunt above. The flowerheads are carried on erect, stout scapes, white and woolly, with lance-shaped scales, purple and ribbed.
The plant is often several feet high, the flowering being about 1 ft. The flowers bloom in March and April. The plant is a herbaceous perennial propagated by division.
In Petasites albus the plant is dioecious, and the male flowerheads are more conspicuous. In the female capitula there are two kinds of florets. Only some in the centre produce honey, and the stamens (usually absent) and pistil (with stigma with short hairs) are functionless, and around these are tubular female florets without honey or stamens. The male flowerheads are loose and of one sort of floret only, and possess honey, and a pistil with no stigma, but a style whose branches sweep the pollen out from the cylinder by means of the hairs, but they possess no papillae. The male capitula, with florets which are tubular below and bell-shaped above, also possess some functionless florets occupying the same place as the pistillate florets in the female flowerheads, which they resemble in not possessing a nectary or stamens, and in having a style and a narrow tubular corolla. There are also abortive female florets which, in reduced number and functionless condition, correspond in primitive hermaphrodite flowerheads or gynomonoecious florets to the functional female florets. The pappus of the female florets is abundant, and adapts the achenes for wind dispersal.
Photo. B. Hanley - Butterbur (Petasites Officinalis, Moench)
Butterbur is a clay-loving plant addicted to clay soil in moist hollows or sandy loam.
It is covered with the same pretty fungus as Coltsfoot, Coleo-sporium sonchi.
The moths, Botys alpinalis, the Butterbur, Hydroecia petasitis, Halonota turbidana, live on it.
Petasites, Dioscorides, is from the Greek petasos, a large, broad-brimmed hat, alluding to the foliage, and the second Latin name refers to its medicinal use.
It is called Batter Dock, Bog Rhubarb, Bogs Horns, Burn-blades, Butter-bur, Cap Dockin, Cleats, Kettle Dock, Water Docken, Dunnies, Eldin, Eldin-docken, Ell-docken, Flapper Dock, Flea-dock, Gallon, Gaun, Lagwort, Pestilence Wort, Poison Rhubarb, Son-before-the-Father, Umbrella Leaves. It was called Pestilence Wort from a supposed remedy it formed for pestilential fevers. The name Son-before-the- Father is given because the flowers appear before the leaves. The name Bog Rhubarb is applied because the leaves are like rhubarb. It is called Bogs Horns because children use the hollow stalks as horns or trumpets. The name Butter-bur is given because people in the country wrapped butter in the large leaves. Eldin is a name given because it was used as elden or fuel.
Essential Specific Characters:164. Petasites officinalis, Moench. - Soboliferous, leaves large, on long furrowed stalks appearing after flowerheads, downy, orbicular, reniform, flowerheads, lilac, in spike, plants dioecious.