Alnus incana

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Alnus incana
Leaves of speckled alder

Secure  (NatureServe)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fagales
Family: Betulaceae
Genus: Alnus
Subgenus: Alnus subg. Alnus
A. incana
Binomial name
Alnus incana
Range map

Alnus incana, the grey alder, tag alder or speckled alder, is a species of multi-stemmed, shrubby tree in the birch family, with a wide range across the cooler parts of the Northern Hemisphere. Tolerant of wetter soils, it can slowly spread with runners and is a common sight in swamps and wetlands. It is easily distinguished by its small cones, speckled bark and broad leaves.[citation needed]


Alnus incana var. tenuifolia male flowers in early spring along the Columbia River

It is a small- to medium-sized tree 15–20 metres (49–66 ft) tall with smooth grey bark even in old age, its life span being a maximum of 60 to 100 years. The leaves are matte green, ovoid, 5–11 centimetres (2–4+14 in) long and 4–8 cm (1+123+14 in) broad. The flowers are catkins, appearing early in spring before the leaves emerge, the male catkins pendulous and 5–10 cm (2–4 in) long, the female catkins 1.5 cm (58 in) long and one cm broad when mature in late autumn. The seeds are small, 1–2 millimetres (132332 in) long, and light brown with a narrow encircling wing. The grey alder has a shallow root system, and is marked not only by vigorous production of stump suckers, but also by root suckers, especially in the northern parts of its range. The wood resembles that of the black alder (Alnus glutinosa), but is somewhat paler and of little economic value.


There are four to six subspecies, some treated as separate species by some authors:


Alnus incana is a light-demanding, fast-growing tree that grows well on poorer soils. In central Europe, it is a colonist of alluvial land alongside mountain brooks and streams, occurring at elevations up to 1,500 metres (4,900 ft). However, it does not require moist soil, and will also colonize screes and shallow stony slopes. In the northern part of its range, it is a common tree species at sea level in forests, abandoned fields and on lakeshores. Several species of Lepidoptera use grey alder as a food plant for their caterpillars. In the boreal forest area of Canada, A. incana is often associated with black spruce in the forest type termed black spruce–speckled alder.[7] The larvae of the alder woolly sawfly sometimes cause considerable defoliation to the grey alder.[8]

A. rugosa provides cover for wildlife, is browsed by deer and moose, and the seeds are eaten by birds.[9]


Pedunculagin is an ellagitannin found in the Manchurian alder (A. hirsuta var. microphylla).[10]


The tree is cultivated in parks and gardens. The cultivar 'Aurea', with green-gold leaves, has gained the Royal Horticultural Society's Award of Garden Merit.[11]

It is sometimes used in afforestation and agroforestry in non-fertile or wet soils which it enriches by means of nitrogen fixing bacteria in its root nodules.

Alder is an excellent tree for coppicing[12] and pollarding. Its cut branches may be fed to browsing livestock such as cows and goats, then used for kindling, firewood, or light construction - while root systems fertilize adjacent agricultural plots via nitrogen fixation.[citation needed]

The Zuni people use the bark of the tenuifolia subspecies to dye deerskin reddish brown.[13]

The Ho-Chunk people eat the bark of the rugosa subspecies when their stomachs are "sour" or upset.[14]

Its wood and bark are used in smoking meat,[15] particularly fish[16] and duck.[17]


  1. ^ Shaw, K.; Roy, S. & Wilson, B. (2014). "Alnus incana". The IUCN Red List of Threatened Species. 208. IUCN. e.T63517A3125479. doi:10.2305/IUCN.UK.2014-3.RLTS.T63517A3125479.en.
  2. ^ Flora of North America 2009.
  3. ^ Jepson Flora Project (ed.). "Alnus incana subsp. tenuifolia". Jepson eFlora. The Jepson Herbarium, University of California, Berkeley. Retrieved January 28, 2013.
  4. ^ "Alnus incana ssp. tenuifolia". Calflora. Berkeley, California: The Calflora Database. Retrieved January 28, 2013.
  5. ^ "Alnus incana". Plants for a Future. Retrieved January 28, 2013.
  6. ^ Patterson, Patricia A. (1985). Field Guide to the Forest Plants of Northern Idaho (PDF). United States Department of Agriculture Forest Service. p. 34. Archived from the original (PDF) on 2022-04-12.
  7. ^ Hogan 2008.
  8. ^ Forest Health Conditions in Alaska—2003. DIANE Publishing. p. 59. ISBN 978-1-4289-6595-9.
  9. ^ Little, Elbert L. (1980). The Audubon Society Field Guide to North American Trees: Eastern Region. New York: Knopf. p. 363. ISBN 0-394-50760-6.
  10. ^ Lee, O.; Choi, M.; Ha, S.; Lee, G.; Kim, J.; Park, G.; Lee, M.; Choi, Y.; Kim, M.; Oh, C. H. (2010). "Effect of pedunculagin investigated by non-invasive evaluation on atopic-like dermatitis in NC/Nga mice". Skin Research and Technology. 16 (3): 371–377. doi:10.1111/j.1600-0846.2010.00443.x. PMID 20637007. S2CID 25752299.
  11. ^ "RHS Plantfinder - Alnus incana 'Aurea'". Royal Horticultural Society. 2012. Retrieved 5 January 2018.
  12. ^ "The Best Species for Coppice Forestry". 15 September 2017.
  13. ^ Stevenson, Matilda Coxe (1915). "Ethnobotany of the Zuni Indians". SI-BAE Annual Report. 30: 80.
  14. ^ Kindscher, Kelly (1998). "Huron Smith's Ethnobotany of the Hocąk (Winnebago)". Economic Botany. 52 (4): 361. doi:10.1007/BF02862065. S2CID 20652394.
  15. ^ "Alder Flavor Profile: The Most Delicate, Earthy Wood Smoke".
  16. ^ "Smoking wood chart | Ultimate guide to the wood you should use". July 2022.
  17. ^ "Best Wood for Smoking Duck: Tips & recipes - Lakesidesmokers". 28 April 2020.

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