Looking for a tree species to help re-establish woodlands on difficult sites or disused farmland? Consider the Alnus incana ssp. tenuifolia, also known as the Mountain Alder or Thinleaf Alder. Its fast growth rate allows for quicker establishment of more permanent woodland trees, and the bacteria on its roots fix atmospheric nitrogen, which can benefit nearby plants. Additionally, the Alder's extensive root system is great for controlling erosion on banks. This species also contributes to building up humus content in soil when its leaves fall in the autumn. While Alder seedlings may not thrive in shady woodland conditions, it can still be a useful pioneer tree. The bark and strobils are a source of tannin, and a dark dye can be obtained from the bark. The wood is durable in water and can be used locally as fuel. Overall, the Mountain Alder is an excellent option for re-establishing woodland.