Country: More mistletoe please, we're British

The parasite from our pagan past could be set for a thriving future if global warming sets in. But what really interests us is the folklore steeped in sex and fertility.

EVERY WEEK in the run-up to Christmas, the car park of the Tenbury Wells auctioneers is swathed in green. Here the annual mistletoe sales take place, setting the price of this Christmas decoration. In recent years costs have risen sharply, thanks to scare stories about a sharp decline.

This is unduly alarmist, according to Harry Green, of the Worcestershire Wildlife Trust: "It's true that as old apple orchards are grubbed up we lose a lot of established plants," he says. "But it's very versatile and perfectly capable of living on other species."

In fact, some people think the plant is expanding in range. It is a warmth- loving plant and Britain is at the limit of its range (where it is largely confined to southern England). A succession of recent mild winters appears to have helped it broaden its distribution and, if global warming makes a significant impact on our climate, it could be set to increase its range.

As a parasite dependent on birds, changing weather patterns benefit it in other ways. Until recently blackcaps were mainly summer migrants, but over the past few years increasing numbers of Continental birds have moved west rather than following other warblers to Africa for the winter.

While the plant is traditionally associated with the mistle thrush (which derives its name from the plant and frequently jealously guards the juicy berries from others), the blackcap seems even more dependent on it. But whichever species consumes the fruit, the next stage of the life cycle is the same. Buried deep in the juicy white flesh (which is poisonous to humans) are little black seeds. These move with the birds, either stuck to a beak which is then fastidiously wiped on a perch, or internally in its gut.

In either case, blackcaps seem increasingly important vectors. Much smaller than a mistle thrush, they are adept at stealing under the beaks of the sentinels and are also more likely to leave the sticky seeds in tighter, more sheltered, crevices.

As the seed germinates it sends out a short, white, root-like structure known as a haustoria, which penetrates the bark of its new host (poplars, limes, hawthorns and field maples as well as apples). From here it works its way into the capillary network to extract water and essential nutrients. As it grows in strength, the haustoria sends out shoots which fork into the familiar ball of fleshy green stems and leaves. Eventually, small green male flowers appear to produce pollen, which is wind-blown on to the female flowers. These then swell to become berries.

Perhaps surprisingly, given the considerable size of the parasite and the quantities which can grow on just one tree, mistletoe seems to do little damage to its host. Ironically, however, it is rarely found on the tree with which it is so frequently associated. Oak-based mistletoe is very unusual - which perhaps accounts for its veneration by the ancient druids who apparently saw this evergreen parasite growing on their most sacred deciduous tree as a sign of divine favour.

It is here that one begins treating the myths with some scepticism. Although the druids undoubtedly valued both plants, it is difficult to separate historical reality from invented tradition. During the 18th century there was a huge upsurge of interest in our pagan past. Many of the more enthusiastic romantics were not averse to creating suitable legends where there was a dearth of information, and it is certainly difficult to trace many of the "druidical" stories beyond about 1750. That said, however, mistletoe undoubtedly has a long association with man, and figures strongly in folklore.

Along with red holly and black ivy berries, the white fruit has ancient links to the festive season and has many local names (Churchman's Greeting in Somerset, Masslin in Suffolk). Many areas also have superstitions based around the plant. For example, it was widely believed to ward off witches and goblins, prompting many rural homes to have a bunch hanging permanently in the house. In Herefordshire, for instance, these were cut on New Year's Eve and hung up as the clock struck midnight while the previous year's bunch was taken down and ceremonially burnt.

Of course, traditionally it has links with fertility. These are probably pagan in origin and may well stem from the fact that, as an evergreen in deciduous trees, it appears alive when everything else is dead. Alternatively, it may be that the pairs of white berries suspended between two suggestively splayed leaves was the origin of its associations with reproduction. In either event, it was commonly used as an aphrodisiac and as an ingredient in fertility potions. Today such beliefs live on in the kissing tradition.

As an increasingly expensive ingredient of the winter's festivities, it may be worth trying to cultivate your own supply. When discarding this year's bunch, try smearing the berries into the bark of garden trees and shrubs. True, the chances of success are low, but with luck you will foster a fascinating plant, create a valuable food supply for local birds - and save yourself a small fortune over the coming years.