Euphorbia hyberna

Euphorbia hyberna L. (Euphorbiaceae)

Irish spurge

Status in Britain: VULNERABLE.

Status in Europe: Not threatened. Endemic.

E. hyberna is remarkably rare in Britain, considering its abundance in Ireland and in parts of western Europe. In Britain it is confined to two small areas, Nance Wood near Portreath, Cornwall, and the Lyn valley, North Devon, on the border with Somerset. It is a plant of openings in woodland, and grows best in places which receive dappled sun for at least part of the day. Nance Wood is mainly oak coppice with some sycamore, but coppicing has now been abandoned, and E. hyberna is in danger of being swamped by Lonicera periclymenum and Rubus fruticosus. Associated species include Anemone nemorosa, Angelica sylvestris, Conopodium majus and Hyacinthoides non-scripta. In the valley of the Lyn, the plant is locally common in ancient, formerly coppiced, oak woodland (FitzGerald 1990b). 

This perennial rhizomatous species grows and flowers early, before the trees have come fully into leaf. It then remains green and leafy through the summer, before dying back to a stout tufted rootstock in autumn. Individual plants can live for at least twenty years.

E. hyberna was first found in Devon in 1840, and in Cornwall in 1883, at which time it was abundant. It has also been reported from Somerset, but has not been seen recently on the Somerset side of the county boundary with Devon (P. & I. Green, pers. comm.). In 1989, more than 40 clumps were reported in Nance Wood, Cornwall. It is under no serious threat in Devon at present, but the spread of Fallopia japonica (which is becoming locally dominant in the Watersmeet woods) and other aggressive aliens could oust it from much of its suitable habitat. In Nance Wood, control of vigorous associates may become necessary.

E. hyberna is endemic to Europe: ssp. hyberna has a typical Atlantic distribution, being found in Ireland, western France, north-west Spain and Portugal; other subspecies occur in the Alpes Maritimes and on Mediterranean islands (Smith & Tutin 1968). In Ireland ssp. hyberna is common in the south-west, from east Cork to North Kerry, and is often a conspicuous feature of hedgebanks in these areas in spring.

There are no other examples of a species so common in south-west Ireland, yet so rare in south-west England. Saxifraga spathularis is equally common in south-west Ireland, and found in similar habitats to E. hyberna, but is not known in Britain. There must be some uncertainty whether E. hyberna is native in England, or whether it is an escape from cultivation or was brought in with cargo from Ireland to Lynmouth and Portreath. Trade between Ireland and North Devon was well developed in the Middle Ages, and seeds could have been introduced with wool for the cloth trade. In Ireland E. hyberna is known as a fish poison, and there is the remote possibility that the plant could have been introduced to take fish from the Lyn. However, there are other examples of highly unbalanced distributions between south-west Ireland and south-west England (e.g. Perring 1996), and most authorities consider E. hyberna to be native in Britain.

M. Rix