Viscum album (mistletoe)

Mistletoe ranges from North Africa to southern England and southern Scandinavia, across Central Europe to southwest and east Asia to Japan. In Europe three subspecies (ssps.), which grow on different species of host trees, have been recognised. Viscum album ssp. album grows on hardwoods, V. album ssp. abietis on fir trees (Abies) and V. album ssp. laxum grows on pines and spruce. Further east there are well-known forms of V.album which have coloured fruits.

In the UK V. album occurs from east Devon to Yorkshire, and is particularly common in central and southern England and around London.

An apple tree killed by mistletoe (Image: Don Kirkup)

Viscum album is locally common in the UK. The most recent survey (1993-6) showed that, in its stronghold in the former apple orchard areas of the Welsh borders, the populations had fallen in numbers as a direct consequence of the decline of the orchards. In spite of this, the plant was still much more common in the counties of Gloucestershire, Herefordshire and Worcestershire, when compared with what are probably more natural frequencies found elsewhere.

Infestations of mistletoe are detrimental to the host tree, and large infestations can eventually lead to the host's death, particularly during prolonged periods of dry weather. As mistletoe reduces the productivity of commercial fruit trees it is often pruned out to try and stop its spread.

Male plant (Image: Don Kirkup, RBG Kew)

Mistletoe has had a long history of use in folk medicine. Druids (members of a priestly class active in Gaul during pre-Christian times) regarded mistletoe growing on oak as superior. Some of the constituent compounds of mistletoe affect the immune, circulatory and cardiac systems. Mistletoe has been used as an antiseptic, antispasmodic, astringent, digestive and diuretic, and, among the many ailments it has been used to treat, are epilepsy, ulcers, high blood pressure, rheumatism and certain types of cancer. Despite experimental anti-tumour effects, research is still underway to determine its clinical role, although the commercially available mistletoe extracts such as Iscador and Helixor are widely used as oncological drugs, particularly in Germany.

Druids used the plant as an aphrodisiac, and in Scandinavian tales it symbolises peace and love. Until the arrival of Christmas trees in the nineteenth century, the kissing bough held centre stage at Christmas, when a berry was plucked with each kiss until none was left. Today, mistletoe is still a favourite Christmas decoration.

Scientists in Kew's Sustainable Uses of Plants Group were commissioned by the Countryside Agency, English Nature and Scottish Natural Heritage to undertake research on the commercial uses of wild and traditionally managed plants in England and Scotland. Border towns between England and Wales, in Herefordshire, Gloucestershire, Shropshire and Worcestershire, are the traditional centres for mistletoe trade. Tenbury Wells (in Herefordshire) has the last remaining specialist mistletoe auctions based on material gathered by local orchard owners and their casual workers. Despite the English harvest, imports - mostly from France - seem to be the source of most seasonal mistletoe in the London markets. In recent years, small amounts of imported French mistletoe have even reached the market at Tenbury Wells, but 99% of mistletoe traded there is still collected in local counties.

Mistletoe contains a mixture of toxic proteins, viscotoxins and mistletoe lectins. The leaves and stems are reported to be more poisonous than the fruits, and there is some evidence that the toxicity depends on the species of tree on which mistletoe is growing. Most problems are likely to arise when mistletoe is cut and brought indoors (for example at Christmas-time), and usually involve children who have eaten the fruits. Reactions vary and depend on the age of the child and the number of fruits eaten. As few as three or four berries may produce mild stomach ache; if large numbers are eaten gastroenteritis and diarrhoea may result. Poisoning is rarely serious, but it is best to seek medical advice. Pets can be at risk; some cases of dog poisoning have been fatal.

Learn about other Christmas Plants

Commercial uses of wild and traditionally managed plants in England and Scotland

Natural History Museum Species of the Day: Viscum album