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Alnus glutinosa
Also called Black Alder, European Alder, Alder, European Black Alder, Black Elder
Common alder is a medium-sized, fast-growing tree native to most of Europe and southwest Asia that thrives in wet ground and is often used for riverbank stabilisation. It grows well in poor soils thanks to nitrogen-fixing bacteria in its roots.
Alnus glutinosa, the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium-sized, short-lived tree growing to a height of up to 30 metres (98 feet). It has short-stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water.
The common alder provides food and shelter for wildlife, with a number of insects, lichens and fungi being completely dependent on the tree. It is a pioneer species, colonising vacant land and forming mixed forests as other trees appear in its wake.
Pollen from the common alder, along with that from birch and hazel, is one of the many sources of tree pollen allergy. As pollen is often present in the atmosphere at the same time as that of hazel, hornbeam and oak, and they have similar physicochemical properties, it is difficult to separate out their individual effects. In central Europe, these tree pollens are the second most common cause of allergic conditions after grass pollen.
The common alder is native to almost the whole of continental Europe (except for both the extreme north and south) as well as the United Kingdom and Ireland. In Asia its range includes Turkey, Iran and Kazakhstan, and in Africa it is found in Tunisia, Algeria and Morocco. It is naturalised in the Azores. It has been introduced, either by accident or by intent, to Canada, the United States, Chile, South Africa, Australia and New Zealand. Its natural habitat is in moist ground near rivers, ponds and lakes but it can also grow in drier locations and sometimes occurs in mixed woodland and on forest edges. In Britain, alder is a key component of various important types of riparian and wetland woodland such as W4, W5 and W6, and there are similar vegetation communities across Europe.
The common alder is used as a pioneer species and to stabilise river banks, to assist in flood control, to purify water in waterlogged soils and to moderate the temperature and nutrient status of water bodies. It can be grown by itself or in mixed species plantations, and the nitrogen-rich leaves falling to the ground enrich the soil and increase the production of such trees as walnut, Douglas-fir and poplar on poor quality soils. Although the tree can live for up to 160 years, it is best felled for timber at 60 to 70 years before heart rot sets in.
Italian Alder · Grey Alder · Himalayan Alder · White alder · Red Alder · Alder
Text excerpted from the Wikipedia article Alnus glutinosa by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.
