The holly on sale in the street now is often "ruthlessly cut down", a county's environmental officer has said.
The hacking of the female holly trees at this time of year for their red berries is done with very little thought for the long-term survival of the tree, according to Mr Micheal O Coileain, environmental officer with Kerry County Council.
"Try to ensure this coming week that the holly you decorate your house with is from a sustainable source," he advised.
The tree once sacred to the Celts is in danger of becoming extinct as it is no longer protected under the Brehon laws. It has also now lost the folk belief, held for centuries, in its sacred nature.
In the Brehon laws, holly is listed as one of the seven noble trees, alongside oak, hazel, yew, ash, pine and apple, Mr O Coileain explained. "It was regarded as an offence to cut down or damage any of these trees," he said.
Under the laws the price for cutting down a holly tree was a milch-cow.
Folklore, and the belief that the tree was a favourite of the fairies or the sioga, also protected it long after the Brehon laws, he added.
The threat to the holly has increased in recent years, when instead of losing a few sprigs the tree is severely stripped and in most cases cut down.
It is an offence to cut down trees by the roadside. Technically a felling licence is needed, Mr O Coileain said.
He has noticed, however, that farmers have begun selling sprigs at farm gates and this, he believes, is more sustainable than the stealing of trees.
"The best way to ensure that the holly survives is to plant some near your home. It is a sturdy plant with up to inches of growth a year. It will also attract birds to your garden," Mr O Coileain said.
However, it is not a good idea to plant the tree too close to the house. Legend had it that if a holly was too near the house the women rarely married and, if they did, never had children.
Gardaí say some traders get permission from farmers, but otherwise they are not entitled to cut down trees from hedgerows or take them from protected areas such as the national parks.