A holly tree grows outside my farmhouse in Pembrokeshire, a joy when laden with scarlet berries at Christmas but a source of irritation in summertime when prickly leaves are shed like drawing pins across the lawn.

I have often pondered about its origins. Specialist holly grower, Philip Lanc, has a delightfully curious explanation. “Holly trees were planted outside houses in Wales to ward off evil spirits; the origins of this tradition dates back to Celtic folklore,” he explains.

I can now sleep easily at night but rest will be in short supply for Philip in the coming days because Christmas is one of his busiest times.

He cultivates around 10,000 holly plants from seeds and cuttings on his smallholding in Carmarthenshire. Unbelievably, there are 400 varieties belonging to the Ilex genus. Understandably he doesn’t grow all of these because it is a business he runs largely by himself, although his wife, Fiona, steps in to help when needed.

This said, he has an impressive range of plants at his nursery at Llyn-y-Gors, St Clears, and they are a sight to behold at this time of the year, adorned with plump berries.

This specialist nursery, thought to be the only one of its kind in Wales, is labour intensive and he has numerous adversaries. Field mice are a major pest, he admits. “Field mice love holly and can cause a lot of damage.”

Holly thrives in most conditions except waterlogged soil. “It can tolerate almost anything but damp. It doesn”t like wet roots,” says Philip.

He grows a mix of male and female plants because without that balance there would be no berries.

It is surprising that birds don’t strip these trees of their vibrant berries as the ground grows hard in winter and their food supply becomes scarce. There are many theories but the most appealing has to be the one that maintains that a thrush will protect a tree bearing berries.

“I was out in the yard the other day and there was a tremendous commotion in one of the trees. I went to have a look and a thrush was very noisily shooing away a blackbird,” says Philip.

It could also have something to do with a chemical reaction which makes berries unpalatable to birds when they reach a certain stage of maturity.

Customers include farmers who use holly in hedging schemes. In modern times farmers like it because its prickly leaf is a good deterrent to livestock but in days gone by they were more likely to have it for reasons of superstition. It was said that cattle would thrive if a piece of holly was hung where it could be seen on Christmas Day. It has been used widely for marking drainage outfalls on farms because it is evergreen. Also, in years past, farmers used holly for cart axles and to stop witches from flying along the hedgerows.

Holly’s association with Christmas dates back to pagan times when it was considered good luck to bring something green and living into the house in the depths of winter.

In fact there are so many stories associated with this one species that it has a cult following in America. “There is a very enthusiastic Holly Society of America, perhaps it has something to do with the settlers going out there and needing a reminder of home,” suggests Philip.

His business is in its infancy but in five years’ time he plans to be at a point where he can sell cut holly as well as plants to satisfy the Christmas market.