Alder (Alnus) is used medicinally and practically: its bark and leaves, rich in tannins and flavonoids, serve as astringent, anti‑inflammatory and diaphoretic remedies for wounds, skin inflammation, sore throats and fevers. Timber is valued for smoking fish, carving, furniture and fuel. Ecologically, alder fixes nitrogen, stabilizes streambanks and is planted for soil restoration and erosion control.

Alder trees are notable as pioneering, wet-soil specialists that stabilize riverbanks and improve poor soils through a symbiosis with nitrogen-fixing bacteria in their root nodules, enriching surrounding plants. They tolerate flooding, sprout readily, and host diverse wildlife. Their dense, water-resistant wood was valued for underwater construction and smoking foods, while early leaf drop and catkins aid nutrient cycling and quick recolonization.

An alder is a deciduous tree or shrub of the genus Alnus (family Betulaceae), common in temperate regions, especially along rivers, wetlands and damp soils. Alders have simple toothed leaves, catkin flowers and small woody cone-like fruiting bodies. Many species host nitrogen-fixing bacteria in root nodules, improving soil fertility, and are used for erosion control, timber and wildlife habitat.

Another name for the alder tree is Alnus, its Latin genus name; it's commonly called the common alder or black alder (Alnus glutinosa). Regional names include tag alder, speckled alder and mountain alder. These names refer to species in the Alnus genus, trees adapted to wet soils and riparian habitats, noted for nitrogen-fixing root nodules that improve soil fertility.

Alder (Alnus species) has traditional medicinal uses: bark, leaves and catkins have been used as astringent, anti-inflammatory and antiseptic for wounds, sore throats, gum problems and joint pain. It contains salicylates, tannins and flavonoids that may reduce inflammation. Clinical evidence is limited and preparations vary. Avoid if allergic to salicylates or during pregnancy/breastfeeding; consult a healthcare professional first.

Alder wood is relatively soft and low-density, denting and scratching easily and offering only moderate strength—unsuitable for heavy structural use or high‑wear flooring. It has limited natural rot and insect resistance, so outdoor use requires preservative treatments and good sealing. Alder can cup or warp during drying or with moisture changes. While it finishes attractively, it needs careful sealing and maintenance to remain durable.