One of the traditional symbols of Christmas may disappear from some areas of the British countryside in the next 20 years, naturalists warned today.
A campaign, led by the National Trust, has been launched to save mistletoe in its English heartland.
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The public are being encouraged to help secure its future by buying sustainably sourced home-grown mistletoe in the run up to Christmas and the office party season.
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The campaign also encourages shoppers to ask where the mistletoe they are buying has come from.
The heartland for mistletoe is cider country - Somerset, Gloucestershire, Herefordshire and Worcestershire - and this is where
it has an uncertain future.
Its main habitat is traditional orchards, which have declined dramatically in the last 60 years.
Peter Brash, a National Trust ecologist, said: "Mistletoe is part of our Christmas heritage and has a special place in a wonderful winter landscape.
"It would be a sad loss if mistletoe disappeared all together from its heartland.
"We could end up relying on imports of mistletoe from mainland Europe for those festive kisses."
Mistletoe is commonly found on fruit trees where it is relatively easy to harvest but can also be seen on other host trees such as lime, poplar and hawthorn across a wider area of the UK.
The best time to sow new mistletoe seeds on host trees is in February and March.
Mistletoe is a parasitic plant which prefers the domestic apple tree as a host.
Data shows that mistletoe distribution is closely linked to that of lightly managed, traditional orchards, particularly in the most prolific mistletoe growing areas of the South West and Midlands.
Traditional orchards have declined by at least 60% since the 1950s - and by up to 90% in Devon and Kent - and with them, an important habitat for the plant.
A project launched by the National Trust and Natural England in 2009 aims to reverse the loss of this habitat by restoring traditional orchards, supporting small cottage industries producing cider and juices and promoting the growth of community run orchards.
In recent years there has also been an increase in the sale of imported mistletoe from Europe, particularly from northern France.
Leading mistletoe expert Jonathan Briggs explained: "Mistletoe benefits
"Unchecked, it will swamp its host tree and ultimately cause it to die.
"Regular, managed cropping will ensure that the host tree remains productive while ensuring that a healthy population of mistletoe will persist."
If mistletoe became more inaccessible because of an ongoing decline of traditional orchards and a loss of its main host, fruit trees, then it might become more a premium product with more scarce supply.
Mistletoe also plays an important role in supporting wildlife.
It provides winter food for birds such as the blackcap and mistle thrush.
It also supports a total of six specialist insects including the scarce mistletoe marble moth, some sap-sucking bugs and the affectionately named "kiss-me-slow weevil" - the Ixapion variegatum.
Mr Brash added: "Ensuring your mistletoe comes from a sustainably managed, British source is good news all round.
"You will be supporting a small home grown industry, while helping to ensure a future for mistletoe and the creatures that are dependent upon
"You'll be kissing with a clear conscience this Christmas."
In the UK mistletoe has long been associated with Christmas and mid-winter customs, probably dating way back into prehistory as a symbol of ongoing life in the winter months.
The kissing custom is a very British version of those ancient traditions.
Over the Channel in France slightly different traditions evolved over time, with mistletoe seen as a good luck symbol at the new year, rather than kissing at Christmas.