Stressed out trees helping charities restore valuable aspen forests

In a little understood quirk of nature foresters have been putting the aspen tree under duress to promote flowering

On a nature reserve deep in the Scottish Highlands there is a polytunnel which houses a small forest of slender grey aspen trees. It is known as the torture chamber".

The aspen is one of the UK's scarcest but most valuable trees. And to produce the tiny, delicate aspen seeds being harvested by the charity Trees for Life, these 104 specimens are deliberately made to suffer.