Gardening: The promiscuous parasite in party mood

Whatever happens beneath the Christmas greenery, mistletoe enjoys its own wanton reputation for opportunism, infidelity and cohabitation. David Foster has been playing gooseberry.

Ever since Adam and Eve's time, apples have enjoyed a certain seductive reputation. And mistletoe, whose potency was first exploited by the Druids, continues to invoke what a Victorian parson once primly described as "a strange spirit of superstitious frivolity too well known to need description".

These two symbols of human desire maintained a clandestine relationship until the mid-19th century, when Dr HG Bull's survey Mistletoe in Herefordshire first revealed them living happily together in local apple orchards.

True to its voluptuous nature, the mistletoe plant begins life by penetrating the timber of its "host" tree, so stimulating a deformity that ultimately grafts both tree and parasite firmly together.

It was fitting that Dr Bull's early study focused on Herefordshire. When the first nationwide mistletoe survey was mounted in 1969-70 by the Botanical Society of the British Isles (BSBI), it established the apple-growing areas of Herefordshire, Worcestershire and Gloucestershire as the undisputed homeland of this wayward plant.

Yet since the war, traditional apple orchards have been disappearing at an alarming rate, with losses of around 90 per cent reported in some counties. Although the decline has been less marked in the Severn Vale, ecologists at BSBI and the wild plant conservation charity Plantlife recently organised a further nationwide survey to assess the effect on the mistletoe population.

Between 1994 and 1996, many thousands of volunteers sent in sightings, including details of the location and species of host trees. Detailed analysis is still going on, but it's already clear that mistletoe retains a firm hold in the Severn Vale.

"There have been both losses and gains", says the survey co-ordinator, Jonathan Briggs. "The new study was immensely popular, and some of the `gains' may simply be the result of more enthusiastic recording. Similar effects have been found in other surveys, and we will have to take this into account when we produce the final report."

Although, as expected, many of the losses are in places where apple orchards have disappeared, mistletoe is naturally promiscuous. Given the opportunity, it will grow happily on some 50-60 tree species, including lime, poplar and hawthorn. Jonathan Briggs remains sanguine: "The evidence from other areas suggests there is no overall threat - mistletoe seems to be doing fine elsewhere."

The practicalities of harvesting are another matter. Because mistletoe is most easily gathered from apple orchards, Jonathan Briggs admits that its changing distribution patterns may affect the origin of Christmas supplies. Mistletoe has been imported from French orchards for many years, he says, and he points out that "the UK market has probably never been self-sufficient".

This year, however, may turn out to be the exception. Nick Champion, auctioneer at England's largest mistletoe market in Tenbury Wells, reports that the Christmas trade has been buoyant.

"We offered 930 lots of between a third and half a hundredweight yesterday," he told me early in December. "We haven't seen any French mistletoe yet this year," he said, and added that the foreign greenery tends to arrive a bit later anyway, because of the distances it has to travel.

Meanwhile, if you're wondering why scientists should be so interested in a parasite that supports just three kinds of bug, a moth, and a good deal of festive ribaldry, remember that the plant's healing properties have been known for thousands of years. The Roman naturalist Pliny recalled Druid priests using mistletoe extracts to cure a variety of ailments, and as a fertility drug for farm animals. Priests cut the mistletoe from the trees with a golden sickle, and caught it in a white sheet to prevent the magical powers from draining away into the soil.

Pagan ritual? Perhaps. But even today, mistletoe is an ingredient in homeopathic remedies for high blood pressure and epilepsy, and is still used for a variety of animal treatments. In Germany and Switzerland, the mistletoe extracts Helixor and Iscador are among several used in the production of modern anti-cancer drugs and, says Jonathan Briggs, "harvesters still take great care to prevent mistletoe coming into contact with the ground".

But as Christmas approaches, mistletoe's main attraction, of course, lies in its romantic appeal. Critics of imported French varieties say that the foreign plants have fewer berries than the English plant, and wilt faster after a cross-Channel journey. There should be no shortage of good English mistletoe in the shops this year - the question is, can you resist the appeal of a French kiss?

For details about Plantlife, the wild plant conservation charity, send a stamped addressed envelope to Plantlife, The Natural History Museum, London SW7 5BD.