A conservation charity hopes to boost wild populations of a rare tree.
Aspens grow in cool regions of the northern hemisphere and in the UK the trees are mostly found in north west Scotland.
Findhorn-based Trees for Life hopes to have created its own source of seeds by encouraging branches to flower under controlled conditions.
In trials, the charity has stimulated aspen branches to flower at its Dundreggan estate near Glenmoriston.
Trees for Life has been running experiments pollinating the trees by hand for two years.
The charity said the trees were at risk because they rarely flower, and collecting seeds from aspen in the wild for propagation is “almost impossible”.
It said that aspens that do flower in the Highlands were often in remote or inaccessible locations, making them hard to reach for collecting seeds – if any should be available in the first place.
Unlike most trees, where male and female flowers occur on the same tree, aspens are either male or female.
Aspens flower in March and April, before the leaves appear, with both male and female trees producing catkins.
Pollinated female catkins ripen in early summer and release tiny seeds.
Under carefully controlled conditions, Trees for Life said it had successfully hand-pollinated female aspen catkins with pollen collected from male trees.
It said the catkins will ripen in a few weeks’ time to produce seeds, which will be sown in the Dundreggan Tree Nursery to produce a new generation of young aspen trees.
Doug Gilbert, Dundreggan operations manager at Trees for Life, said encouraging the branches to flower in the trials was a “major breakthrough” for the charity.
He added: “Having a seed supply to grow a new generation of aspen will help us transform the fortunes of a beautiful tree that provides a habitat for a wide range of organisms including mosses, lichens and invertebrates – many of which are rare and endangered in Scotland.”