About this tree
Alnus glutinosa, or black alder, is native to much of Europe and thrives in wet soils along rivers, streams, and wetlands. Reaching heights up to 30 m, it is fast-growing and easily identifiable by its rounded, glossy green leaves that remain late into the season before turning yellow. Its bark is dark and slightly fissured. In early spring, before leaves appear, the black alder produces both male catkins and small, cone-like female structures, which persist through winter and feed birds such as siskins and redpolls. Alders are notable for their root nodules, which host nitrogen-fixing bacteria, enriching soils where they grow. Ecologically this trait makes them pioneers in the initial forestation of poor or disturbed land. The tree supports a high number of insect species and provides shelter for amphibians in wetland margins, including the mill race frogs at the Klostergut. Its resilience in wet habitats makes it a vital species for stabilizing riverbanks and supporting aquatic biodiversity. Because the black alder’s wood is resilient to water, it has been used in the past for wooden pipes and other elements in hydraulic engineering and in underwater construction, such as in the foundations of Venice.