Nature Notes - Butterbur by Ian Brand

Out cycling at this time of year, I often pass what from a distance look like rather strange pink hyacinths. These are the flowers of the Butterbur (Petasites hybridus).

Most people will recognise butterbur once in leaf (but maybe not in flower), with its large round rhubarb-like leaves growing along riverbanks, ditches and damp road verges and forming extensive patches to the exclusion of other plants.

What is often missed in spring, or misidentified as a different plant are the flower heads, which appear before the leaves. Another example of “flowers before leaves” seen this time of year is the dandelion-like Coltsfoot. This botanical phenomenon is uncommon in herbaceous plants but is much more common amongst trees and woody shrubs like the Blackthorn or Sloe with its masses of white blossom on leafless branches.

Butterbur is dioecious, i.e. plants being either male or female. The male plants are found throughout the UK but the female only in the North of England and Midlands (so the Northern male butterburs are the lucky ones, with the possibility of romance denied to their Southern brothers!). Spread and propagation is therefore mainly by vegetative means with fragments arising from the underground rhizome.

It can often be difficult to tell if you are looking at a male or female plant unless you get your magnifying lens out. The easy way to spot the difference is to wait until early summer when the female spike will remain above the leaves, while the male has died back and disappeared.

A surprising fact to most people is that the Butterbur is a member of the daisy family (Asteraceae). The inflorescence or flower-head consists of flowers which are themselves divided further into smaller florets, just as in fellow family members, the thistles.

Both its scientific and common English names are well chosen. Petasites derives from the Greek petasos, meaning broad-brimmed hat, which echoes the large leaves, which keep growing throughout the summer, reaching up to 90cm in diameter. The common English name; “Butterbur” describes how the leaves were once used for wrapping butter before the days of refrigeration. Feel a leaf and you will understand why. It is not only large and pliable to fold without breaking, and thick enough to cushion the butter, but also feels cool with a white downy underside to the leaf. You could still use it today as an emergency picnic wrapper for left-overs, although its favoured habitat of damp ditches might not be the best place to spread your picnic rug.