Prisoners urged to hug trees in drive to identify oldest woodland survivors

Prisoners are being let out of their cells to hug trees.

But it's not only for their own well-being. They are taking part in a drive to find the country's most ancient trees.

Linking hands with others to encircle a tree provides a rough measure of its girth and gives a clue to its age.

HM Prison Service is one of the many partners in the Ancient Tree Hunt, a five-year project launched by the Woodland Trust and funded by Lottery money.

The hunt aims to find 100,000 ancient trees across Britain - and some of these will be in prison grounds.

'Many prisons were established in old stately homes,' said Woodland Trust official Jill Butler.

'Where you've got a stately home you have parkland and those old parklands will have the ancient trees. Some of the people in the prisons will help us record them because it's not very easy to send people from outside in.'

Prisoners keen to boost their chances of points for good behaviour will no doubt welcome the chance to help.

A British standard hug from an adult with arms outstretched and finger tip to finger tip is about 1.5 metres. A veteran oak might be a candidate for the Hunt's database once it gets to a minimum of three adult hugs, a beech might qualify at just two hugs and a sweet chestnut needs to be four hugs, as this species grows more quickly.

Once an old tree is identified a trust 'verifier' confirms its age.

Ms Butler added: 'The Prison Service have their own plans to look after the biodiversity and the heritage of the areas they own and part of that is to take part in the Hunt and know what sort of trees they've got in there.'

She added: 'I went inside a prison south of Birmingham and they've got some very large sweet chestnuts which are ancient. They're part of the old parkland which was there before the prison was established.'

One of the Hunt's findings is that some ancient trees have effectively 'walked' across the landscape by putting down roots where their branches come into contact with the soil - like a hand walking on its fingers.

Ms Butler said: 'When the branches touch the ground they can root and then you'll generate a new tree. That process can happen again and again and again. They could live for eternity.

'Alternatively if a tree falls it can put up lots of limbs which then grow into a tree which is exactly the same.

'One old oak I found had done it three times and simply leapfrogged across the landscape.'

The Woodland Trust has launched a website with interactive maps.