E-Flora BC: Electronic Atlas of the Flora of British Columbia

Alnus incana subsp. tenuifolia (L.) Moench (Nutt.) Breitung
mountain alder (thinleaf alder)
Betulaceae (Birch family)

Introduction to Vascular Plants
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Distribution of Alnus incana subsp. tenuifolia
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Species Information

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Deciduous shrub or tree, up to 12 m tall, usually 2-5 m tall, new growth short-hairy; axillary buds with short stalks; bark scaly, often lichen-covered, yellowish-brown or grey.
Alternate, deciduous, smooth, coarsely to irregularly toothed, the teeth pointing outwards, leaf margins not rolled under, brownish in the fall.
Inflorescence of male and female catkins, which open before the leaves on previous year's growth; male catkins with stalks.
Small nutlets, without wings; female cones 1-1.5 cm long, egg-shaped.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Early Spring
Fruit/Seed characteristics:
Colour: Brown
Present from Summer to Fall
Source:  The USDA

Habitat / Range

Moist forests, streamsides, bogs and fens in the montane zone; common in BC east of the Coast-Cascade Mountains; N to AK, YT and NT, E to SK, and S to NM, AZ and CA.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Alnus incana ssp. tenuifolia

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 393 1046 1693
Slope Gradient (%) 0 10 80
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
0 45 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
1 5 7
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BG(1), BWBS(6), ESSF(16), ICH(38), IDF(22), MS(27), PP(1), SBS(50)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Alnus purpusii Callier
Alnus purpusii Callier
Alnus incana var. occidentalis subsp. rugosa (Dippel) C.L. Hitchc.
Alnus incana var. occidentalis (Dippel) C.L. Hitchc.
Alnus incana var. virescens S. Wats.
Alnus tenuifolia Nutt.
Alnus tenuifolia var. occidentalis (Nutt.) Breit.

Taxonomic and Nomenclatural Links

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General References