Common Alder

The common alder is a medium-sized deciduous tree belonging to the birch family Betulaceae, native to almost the entirety of Europe, southwest Asia, and parts of north Africa. It is widely recognized for its strong preference for damp, wet habitats such as riverbanks, marshes, and swampy woodlands, where its extensive root system helps stabilize soils and prevent erosion. The tree forms a symbiotic relationship with the nitrogen-fixing bacterium Frankia alni, which allows it to thrive in nutrient-poor soils by enriching the surrounding earth. Its glossy dark green leaves remain on the tree relatively late into autumn before dropping green. The common alder is also notable for producing woody, cone-like female catkins that persist through the winter months, providing food and habitat for various local wildlife species.