Pain for gain Aspen trees left to suffer so species can thrive

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

- Severin Carrell

The aspen is one of the UK's scarcest but most valuable trees. To produce the tiny, delicate aspen seeds being harvested by the charity Trees for Life, these 104 specimens have been deliberately made to suffer. They may have been water-starved, or had their limbs trimmed or their trunks sliced and ringed, the slivers of bark rotated or put back upside down. And despite the ice-cold chill and the snow falling outside, leaf buds are starting to form.

It seems paradoxical but it works: being stressed helps these aspens flower and produce the short-lived seeds that rewilding charities need in their efforts to restore the aspen forests that once thrived across Britain's uplands.

In a little-understood quirk of nature, UK aspens rarely flower in the wild and very rarely cross-germinate each other. Most live isolated lives, often clinging to rocky slopes to escape sheep and deer, the male trees too far apart to naturally fertilise with females.