It's the first time trees are being given away

Visitors can also have pine and birch seedlings which threaten to dry out and destroy the bog at Fenn's Whixall and Bettisfield Mosses nature reserve, near Wrexham.

The Countryside Council for Wales and England Nature are trying to mend the peat bog - around 1,500 acres and the third biggest bog in Wales - and make it an active wetland.

The peat bog is precious because it attracts rare birds of prey as well as the rare Heath butterfly and the white-faced darter dragonfly.

"On Fenn's Moss, by getting their Christmas tree, visitors can help us to nip this problem of invading pines in the bud," said Dr Joan Daniels, site manager.

The Fenn's Moss National Nature Reserve

"They are saving part of Britain's boggy biodiversity before the pines take over, and they can have good fun at the same time.

"In the 1960s conifer plants were put around the edge on the areas of the nature reserve which hasn't been restored yet.

"We are trying to mend it but it has also been damaged by putting in ditches."

The bog has gradually been drying out because of pine and birch trees seeding as well as peat cutting for use in gardens.

By building dams rainwater can be retained and wildlife encouraged back to the reserve.

"People don't realise peat bogs are so rare, we have less than 6% of raised peat bogs left in the UK," said Dr Daniels.

Anyone who wants to take a tree on Sunday 7 December must book a place.