Practical ecological knowledge for the temperate reader.

Green Alder/Sitka Alder - Alnus viridus

Other Names: green alder (green alder (ssp. crispa); Sitka alder (ssp. sinuata))[E-flora]

Fuel, Smoke, Insect Repellent Rheumatism

"Alnus viridis crispa is a deciduous Shrub growing to 3 m (9ft) by 3 m (9ft). It is hardy to zone (UK) 4. It is in flower from Apr to May. The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by Wind. It can fix Nitrogen.
Suitable for: medium (loamy) and heavy (clay) soils and can grow in heavy clay and nutritionally poor soils. Suitable pH: acid, neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil." [PFAF]

Subtaxa Present in B.C.

A. crispa. A. sinuata. [PFAF].

Status: Native. [E-flora]
General: Deciduous shrub or tree, 1-5 m tall; pointed axillary buds without stalks; bark scaly, sometimes lichen-covered, yellowish-brown or grey. [IFBC-E-flora]
Leaves: Alternate, deciduous, smooth, finely toothed 1-2 times, oval with pointed tips, 4-10 cm long, brownish in the fall. [IFBC-E-flora]
Flowers: Inflorescence of male and female catkins which open at the same time as the leaves on current year's growth; male catkins unstalked. [IFBC-E-flora]
Fruits: Small nutlets, with broad wings; female cones 1.5-2 cm long, egg-shaped. [IFBC-E-flora]

Habitat / Range Moist slopes, streambanks, avalanche tracks, bogs and fens in all zones; ssp. crispa frequent in N BC, ssp. sinuata common throughout S BC, becoming less frequent and transitional to ssp. crispa in N BC; circumboreal, E to PQ and S to NC, MN, CO and CA. [IFBC-E-flora]

"All local alder species are shrubs or small trees. Alnus crispa subsp. crispa and subsp. sinuata are widespread across northern and northwestern North America, extending into northeastern Russia. Alnus incana subsp. tenuifolia is found in northwestern North America. These species are found across all of Alaska except along the arctic coast." [Jernigan EYK]

Two subspecies occur in BC:
1. Leaf margins shallowly lobed as well as finely saw-toothed..................... ssp. sinuata (Regel) A.& D. Love
1. Leaf margins not at all or only slightly lobed, mostly merely finely saw-toothed..................... ssp. crispa [Ait.] Turrill [IFBC-E-flora]

A "recent study of the alders (the genus Alnus) of the world resulted in American green alder (Alnus crispa) and Sitka alder (Alnus sinuata) being changed from separate species to subspecies of Alnus viridis. Under this new nomenclature, American green alder becomes Alnus viridis subsp. crispa (Ait.) Turrill and Sitka alder becomes Alnus viridis subsp. sinuata (Regel) Love & Love. In the same study, thinleaf alder is renamed from Alnus tenuifolia to Alnus incana subsp. tenuifolia (Nutt.) Breitung." [Viereck ATS]

Other Uses

Medicinal Use

"Indications (Green Alder) - Anorexia (f; DEM); Arthrosis (f; DEM); Bleeding (f; DEM); Childbirth (f; DEM); Constipation (f; DEM; MIC); Cramp (f; MIC); Dentistry (f; DEM); Diphtheria (f; MIC); Dropsy (f; DEM); Dysmenorrhea (f; DEM); Fever (f; DEM; MIC); Gas (f; DEM); Gastrosis (f; DEM); Gonorrhea (f; DEM); Infection (f; DEM); Lameness (f; MIC); Nephrosis (f; DEM; MIC); Neuralgia (f; MIC); Pain (f; MIC); Rheumatism (f; DEM; MIC); Sore (f; DEM); Toothache (f; DEM); VD (f; DEM); Wound (f; DEM; MIC)" [HMH Duke]


Pinosylvin methyl ether - Antifungal; insect antifeedant (“Showshoe Hare” Lepus americanus). [EncyTCMV.4]

"Alaskan green alder (Alnus crispa) produces a resin in buds, catkins, and internodes in which the primary constituents are pinosylvin and pinosylvin methyl ether (Clausen et al. 1986). Concentrations of pinosylvin methyl ether by itself on older buds and catkins are sufficient to account for their rejection by snowshoe hares (Bryant et al. 1983). In winter, however, internodes of both saplings and mature plants are defended against hare browsing by both pinosylvin and pinosylvin methyl ether, with the current year’s growth of the saplings containing three times more of both compounds than that of adults." [Langenheim PR]


"Activities (Green Alder) - Abortifacient (f; DEM); Astringent (1; DEM); Carminative (f; DEM); Depurative (f; MIC); Emmenagogue (f; DEM); Hemostat (f; DEM); Insectifuge (f; DEM); Laxative (f; DEM; MIC); Tonic (f; DEM)." [HMH Duke]


"This pioneer species follows disturbances such as landslides, logging, or glacial retreat. It requires mineral soil seedbed and develops rapidly on moist sites but grows on soils too sterile for other trees. Sitka spruce often becomes established at the same time. Alder acts as a nurse tree, improving soil conditions, and adding organic matter and nitrogen. It thrives with overhead light but is intolerant of shade and disappears from the stand when overtopped by Sitka spruce. Being smaller and hence more quickly overtopped, Sitka alder is probably not such a serious competitor as red alder on logged areas." [Viereck ATS]

Plant Associations: "...people explained to me that spiny wood fern (Dryopteris expansa) rootstock, ... a formerly important carbohydrate food, was associated with... (Alnus crispa) and that one should look for it in a “ravine”..." [Johnson TSTP]

Poplus balsamifera is allelopathic vs. Alnus crispa. Seedling growth, radicle growth, and nodulation are affected. Water-soluble chemicals. Experiment performed in-vitro. [Zeng ASA]

Ectomycorrhizal Fungi

"Varga (1998) found 14 and 31 distinct ECM RFLP variants for Sitka alder (Alnus crispa var. sinuata (Regel) Hulten) and lodgepole pine (Pinus contorta Dougl. ex Loud.)..." [Mah2001]


  1. [E-flora] viridis&redblue=Both&lifeform=4, Accessed Jan 11, 2015
  2. EncyTCMV.4 - J. Zhou et al., Encyclopedia of Traditional Chinese Medicines Molecular Structures, Pharmacological Activities, Natural Sources and Applications: Vol. 4: Isolated Compounds N-S, DOI 10.1007/978-3-642-16779-9, © Springer-Verlag Berlin Heidelberg 2011
  3. Mah2001 - The impacts of broadcast burning after clearcutting on the diversity of ectomycorrhizal fungi associated with hybrid spruce seedlings in central British Columbia, Karen Mah, Linda E. Tackaberry, Keith N. Egger, and Hugues B. Massicotte, Can. J. For. Res. 31: 224–235 (2001) © 2001 NRC Canada
  4. [PFAF], Accessed Jan 11, 2015

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