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Montana Animal Field Guide

Montana Field Guides

Red Alder - Alnus rubra

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Species of Concern

Global Rank: G5
State Rank: S2S3
* (see State Rank Reason below)

Agency Status
MNPS Threat Rank: 3

External Links

State Rank Reason (see State Rank above)
Rare in Montana, where it occurs only in the extreme western portion of the state. The species is at the eastern end of its range in the state.
  • Details on Status Ranking and Review
    Red Alder (Alnus rubra) Conservation Status Review
    Review Date = 06/01/2012
    Population Size

    Score3 - Vey Small: Generally <2,000 individuals.


    Range Extent

    Score1 - Peripheral, Disjunct or Sporadic Distribution in MT: Widespread species that is peripheral, disjunct or sporadically distributed within MT such that it occurs in <5% of the state (<7,500 sq. miles or the combined area of Beaverhead and Ravalli Counties) or is restricted to 4-5 sub-basins.

    CommentPeripheral in northwest Montana

    Area of Occupancy

    Score2 - Low: Generally occurring in 4-10 Subwatersheds (6th Code HUC’s).



    ScoreNA - Rank factor not assessed.



    Score0-1 - Low to Medium.


    Intrinsic Vulnerability

    Score0-1 - Low to Moderate Vulnerability.


    Environmental Specificity

    Score1 - Moderate: Species is restricted to a specific habitat that is more widely distributed or to several restricted habitats and is typically dependent upon relatively unaltered, good-quality habitat (C Values of 5-7).


    Raw Conservation Status Score

    Score 7 to 9 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
Tree to 20 m with gray bark. Twigs reddish with club-shaped buds. Leaf blades to 15 cm long, with revolute margins 1 to 2-times serrate, gray, pubescent and glandular below. Inflorescence borne on twigs of previous season. Fruit with wings to half as wide as nutlet (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Catkins develop in March-April.

Species Occurrences
Number of Species Occurrences: 5
*Not all Species Occurrences are mapped


Range Comments
In MT only in Sanders and Mineral counties; coastal AK and YK south to CA, east to ID and MT (Furlow 1997 in Fl. N. Amer. Vol. 3).

Summary of Observations Submitted for Montana
Number of Observations: 5

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)


Ecological Systems Associated with this Species

  • Additional ReferencesLegend:   View WorldCat Record   View Online Publication
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    • Lesica, P. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX.
    • Little, E.L., Jr. 1979. Checklist of United States trees (native and naturalized). Agriculture Handbook No. 541. U.S. Forest Service, Washington, D.C. 375 pp.
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Citation for data on this website:
Red Alder — Alnus rubra.  Montana Field Guide.  Montana Natural Heritage Program.  Retrieved on November 27, 2015, from
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