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Petasites hybridus - Butterbur

Phylum: Magnoliophyta - Class: Equisetopsida - Order: Asterales - Family: Asteraceae

Petasites hybridus, Butterbur, on a roadside verge, Wales UK

This distinctive spring wildflower often forms dense patches of colour in sheded boggy places and on disturbed roadside verges. The flowers appear before the leaves, and as summer approaches the flowers decay while the leaves continue to grow bigger, eventually looking rather like rhubarb.

Flowers of Petasites hybridus, Butterbur

Identification

Fowering spikes emerge from the ground in March before the leaves appear, and the flowers persist through April and often well in to May. The toothed, heart-shaped leaves usually emerge in early May and continue growing until late summer, by which time they can be up to a metre across. Although matt or felt-like and mid green on their upper surfaces, the leaves have light-grey and distinctly hairy undersides.

Male and female flowers occur on separate plants (so this is a dioecious species, literally meaning having two houses'); however, in Britain it seems that male plants are quite a rarity. Female inflorescences can be up to 70cm tall, while male plants are reported to be much shorter and more squat on average and with more densely-packed flowerheads. Each floret comprises typically 15 to 25 individual five-petalled pink flowers.

Habitat

Most often seen in damp, shaded places such as wet meadows, damp woodlands, stream banks and ditches, Butterbur is particularly conspicuous when it colonises disturbed roadside verges and waste land.

Distribution

Petasites hybridus is native to much of northern and central Europe including Britain and Ireland, where it is quite a common sight. It's range (possibly due to introduction) extends as far north as Finland and southwards into Spain. To the east the range of this species extends into much of Asia

Blooming times

In Britain and Ireland Butterbur produces its flowers from March to May.

Flowers of Petasites hybridus, Butterbur

This member of the asteraceae family of flowers is also sometimes referred to as Bog Rhubarb.

Similar species

An introduced species, Petasites albidus, is very similar but has white flowers. Another, earlier-blooming wildflower with which Butterbur is sometimes confused is Winter Heliotrope, Petasites fragrans; as its scientific name suggests, this is a scented flower, whereas Butterbur has no discernible scent. The other obvious difference is that there are far fewer flowers on the lax spikes of Winter Heliotrope, whose leaves are much smaller than those of Butterbur.

Flowers of Petasites hybridus, Butterbur

The Butterbur specimens shown on this page were photographed in Wales during May.


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