When it comes to choosing this year's Christmas tree, you're faced with several choices. Should it be a completely traditional natural Christmas tree, and should it be organically or conventionally grown? Maybe this year you'll buy a plastic tree, it's smart and can be used again year after year. We asked Peter Hartvig, Principal Investigator at the Department of Agroecology at Aarhus University, who is an expert on Christmas trees, to give his take on the most sustainable Christmas tree. 

"The latest research shows that when we talk about sustainability, the traditional Christmas tree that grows in nature is superior to the plastic Christmas tree," he explains. 

Figures from a life cycle analysis by the University of Copenhagen also show that a plastic Christmas tree actually needs to last 12-16 years before it will be as sustainable as a natural tree. 

"Plastic Christmas trees last an average of 5 years, so there's a long way to go to reach 16 years. Another problem with plastic Christmas trees is that the materials cannot be recycled. It is simply not possible to separate the plastic from the metal," explains Peter Hartvig. 

Another point is that CO2 is emitted during the production of the plastic Christmas tree, whereas the natural Christmas tree absorbs CO2 as long as it grows in the field.

Climate or environment? 

So, is everything just fine and dandy if you choose a natural tree? The answer is no, because there are several sustainability considerations to take into account. Do you want a conventional, organic or even a potted Christmas tree? Because there are differences between natural Christmas trees. And according to Peter Hartvig, you have to decide what is more important: climate or environmental considerations? 

"From a climate point of view, a conventional tree is actually more sustainable. But from an environmental point of view, an organic Christmas tree is more sustainable, as no pesticides or fertilisers are used in organic production," explains Peter Hartvig. He says that the conventional Christmas tree is more climate-friendly, as it grows faster than the organic one and therefore absorbs more CO2. In addition, mechanical weeding is carried out in organic production, which leads to CO2 emissions when the machines burn diesel. 

Think about how you transport your tree

"This brings me to the point that it is actually the transport of the Christmas tree that is the biggest climate polluter. If we all get in our cars and drive 25 km to a forest and pick up a Christmas tree, it's much more climate damaging than if you go down to the local Christmas tree seller, where many trees are transported at once," explains Peter Hartvig. 

Again, there is a difference between natural trees, because while felled Christmas trees can be packed and stacked to fit many on a truckload, potted trees take up much more space during transport, and are therefore not the most climate-friendly choice in the first place. On the other hand, the potted tree wins in the long run, but only if you manage to grow it in your garden after Christmas. Here, according to Peter Hartvig, you have to be extra careful and choose a tree that has grown in the pot from the start. Trees that have been dug up for the occasion are unlikely to continue growing in the garden. This is because the trees have a taproot, which must be intact for them to survive, and it rarely is on dug-up trees. And according to Peter Hartvig, you also need to take extra care of your Christmas tree while it's in your living room, otherwise it won't grow in the garden.  

My sustainable Christmas tree

So, which tree does the expert choose? 

"I used to grow Christmas trees myself on my small property, but they are now far too big. So, I get my tree from the local Christmas tree seller, and of course I have to have the traditional natural conventionally grown Christmas tree," he says.