A tree that will reach your ceiling is likely to be 14 years old or more

It is a serious industry, especially in Denmark, which is already the biggest exporter of Christmas trees and plans to double its production in the next decade.

Every December, millions of trees are felled for no better reason than to look pretty for a fortnight or so, and then to be thrown on the fire.

But in terms of the two millennia since the original Christmas celebration, the tradition of the Christmas tree is barely out of its infancy.

Real Christmas trees remain popular

The first trees were used for seasonal decoration in the middle of the 19th Century, but it is only in the last 40 years or so that Christmas trees have become an essential part of Yuletide celebrations for the vast majority of families in Europe and North America.

Count Grav Johan Scheel has a conifer plantation to the west of Copenhagen. His family has been growing Christmas trees commercially for more than four decades.

Denmark's soil and climate were ideal, he said, for the cultivation of Abies Nordmannia - in his view, the perfect Christmas tree.

These trees do not shed their needles the moment they are chopped down, he said. They grow with a pleasing symmetry, and can be relied upon to produce foliage so thick that you will not be able to see your mother-in-law through the branches - the ultimate accolade for a Christmas tree, according to Danish folk lore.

Risky business

But this is not a business in which you can make a quick buck. It takes at least six years for a Christmas tree to grow big enough to be sold. A tree that will reach your ceiling is likely to be 14 years old or more.

It takes about 30 years for a Christmas tree to produce cones

Add to that the fact that a late frost can ruin a tree, aphids love them, and as many as 55% of all Christmas trees are simply the wrong shape to sell, and you will begin to see the risks involved.

But they do say that fortune favours the bold, and half of all the profits made in Danish forestry now come from the production of the Abies Nordmannia.

It is now such a serious business that scientists devote their lives to the cultivation, development and improvement of the Christmas tree.

Ulrik Brauner Nielson, from the Danish Centre for Forest, Landscape and Planning, is among them. We met in a large greenhouse on the outskirts of Copenhagen where he was clipping and methodically arranging tree branches for testing in a freeze chamber to gauge their reaction to frost.

If the seed stock can be improved, and forestry improved, the number of trees that have to be thrown away can be reduced, he explained.

But again, there are no quick answers. It takes about 30 years for a Christmas tree to produce cones, and therefore seeds. And of course by the time they are 30 years old, all the best looking trees have been chopped down and sold for decoration.