Alder

Alder is a genus of trees and shrubs in the birch family, Betulaceae, known scientifically as *Alnus*.

Alder is a genus of trees and shrubs in the birch family, Betulaceae, known scientifically as *Alnus*. Most species grow in the temperate and cold regions of the Northern Hemisphere, especially in moist or wet habitats. Alders are notable for their catkins, their ability to improve poor soils, and their use in riparian planting and wood production.

Description

Alder is a genus of mostly deciduous trees and shrubs with simple alternate leaves and catkins. The female catkins become woody cone-like structures after fruiting, which is a characteristic feature of the genus.

Distribution and habitat

Alders are native mainly to cool and temperate regions of the Northern Hemisphere. They commonly grow in moist habitats such as stream banks, floodplains, marshes, and other wet soils.

Ecology and uses

Alders are valued for their ability to stabilize riverbanks and improve damp soils. Their wood has been used in sculpture, pulp making, and some construction applications, while several species are also planted as ornamentals or shelter plants.

Notable species

Commonly mentioned species include the common alder (*Alnus glutinosa*), grey alder (*A. incana*), Italian alder (*A. cordata*), and green alder (*A. viridis*). Source material also notes regional variation in which species are present.