Aspen, populous tremula (Crithen or Eadha in Gaelic) grows throughout Europe. In Scotland it is our only native poplar. Now marginalised by many centuries of grazing, it is usually only to be found clinging to cliffs and sides of steep ravines, where animals cannot reach.
The most notable characteristic of this slender tree is its long-stemmed, frilly-edged, rounded leaves, which tremble in the wind. On a breezy day it is as if the tree is cheerfully waving at you.
The aspen usually reproduces by sending up fast-growing suckers, which spread year on year. What looks like a small aspen wood is genetically only a single tree. This means that sexual reproduction and seed production is rare in Scotland, especially since aspen seem to produce catkins only after a warmer summer. Aspen only flowers occasionally, producing male and female catkins on different trees but the population is so sparse that the two sexes seldom occur on the same site. When there was good flowering in Scotland about fifteen years ago, one forester organised collection of flowering branches from male trees and drove them around to scatter pollen over catkins on females in other stands, thus getting much improved seed set. Seed set is rare, so there is a need to propagate aspen from cuttings.
Traditionally, aspen wood has been used for matches but there is now interest in using it commercially for firewood and timber. In the Highlands, the sound of the aspen’s rustling leaves was said to be an omen. At the moment the omens look good, as it is being planted in many places, most notably in Renfrewshire by EADHA, who will be planting their millionth aspen this month!
As aspen is rare in the Southern Uplands, it is hard to know what its distribution would have been in a more pristine environment. There are still examples of big trees present in a few old oak woods fairly low down, but aspen may have been more typical of high level slopes and cleuchs. With this in mind, BFT have planted plenty of aspen near the bottom of Carrifran valley, but also many much higher up. We do know that aspen needs reasonably decent soil and struggles above about 550 metres altitude.
There are aspen stands in two cleuchs (ravines) opposite the Grey Mare’s Tail from which BFT have collected root cuttings for propagation. There is also one aspen actually on the Grey Mare’s Tail cascade. Around 2003, our Site Officer Hugh, an experienced climber, was able to access this and take a cutting, with the assistance of Stan Tanner – a MRT member. These stands are probably surviving relics of much wider distribution, and each stand is often a single clone (ie all trees genetically identical).
At Carrifran Wildwood, we have planted trees propagated from about 18 separate stands within about 40 miles of the site, and hope to have catkin production and sexual reproduction in future. This type of reproduction would increase the genetic diversity and the potential for future evolutionary change, for instance in response to climate change.
At Gameshope Valley, there is a surviving stand (see pic) that is now expanding rapidly, but BFT are also planting more elsewhere on the site.