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Montana Field Guides

Gray Aster - Eurybia glauca
Other Names:  Aster glaucodes, Herrickia glauca

Native Species

Global Rank: G4G5
State Rank: S3S4
(see State Rank Reason below)

Agency Status


External Links

State Rank Reason (see State Rank above)
See rank details.
  • Details on Status Ranking and Review
    Gray Aster (Eurybia glauca) Conservation Status Review
    Review Date = 09/04/2012
    View State Conservation Rank Criteria
    Population Size

    Score1 - Moderate: Generally 10,000-100,000 individuals.

    CommentPopulation size is unknown for Montana, but due to its limited distribution is estimated to be <100,000 plants.

    Range Extent

    Score3 - Local Endemic or Very Small Montana Range: Generally restricted to an area <10,000 sq. miles (equivalent to the combined area of Phillips and Valley Counties) or <6 Sub-basins (4th code watersheds) Range-wide OR limited to one Sub-basin in Montana

    CommentIn Montana, the species is known from Carbon County, though may also occur in Big Horn County.

    Area of Occupancy

    Score1 - Moderate: Generally occurring in 11-25 Subwatersheds (6th Code HUC’s).

    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).


    ScoreNA - Rank factor not assessed.

    CommentTrends are unknown, though habitat is generally stable and populations have probably not declined significantly.


    Score0-1 - Low to Medium.

    CommentThreats to the species' viability appear to be insignificant to low.

    Intrinsic Vulnerability

    Score0 - Low Vulnerability: Species does not have any unusual or specific life history or biological attributes or limted reproductive potential which makes it susceptible to extirpation from stochastic events or other adverse impacts to its habitat and thus slow to recover.

    CommentNo specific factors are known which are believed to increase the species' vulnerability.

    Raw Conservation Status Score

    Score 6 to 7 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
Gray Aster is a perennial with simple or branched, mostly hairless stems that are 20-70 cm tall, and arise from rhizomes with many stems forming colonies. There are numerous alternate, stalkless, entire margined leaves that are 4-12 cm long by 0.5-2.5 cm wide and are hairless and glaucous. The lowermost leaves are smaller and scale-like. The flowers are borne in several to many composite heads of ray and disk flowers surrounded by an involucre of bracts borne on spreading branches. The involucre is 6-9 mm high and is composed of several series of overlapping bracts; the outer bracts are broad and firm, and the inner bracts are narrower and longer and often have purplish tinged midribs. The 8-19 strap-shaped rays are pale lavender and 8-18 mm long by 1-2 mm wide. The disk is 7-12 mm in diameter and consists of numerous flowers with tubular corollas that are shorter than the rays. The bases of both ray and disk corollas are encircled by a pappus of slender white bristles. Achenes are hairless or sparsely short-hairy near their tip.

Flowering in August.

Diagnostic Characteristics
It is distinguished from other similar species previously classified in Aster in Montana by the combination of the rhizomatous perennial habit, glabrous stems and glaucous leaves, and an involucre of broad stiff bracts that are green only on the midrib and tip.

Species Range
Montana Range Range Descriptions


Range Comments
In Carbon County MT, south to AZ and NM (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 20

(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)

Limestone outcrops and shallow soils with limestone parent material.

The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus vagans, Bombus ternarius, and Bombus terricola (Colla and Dumesh 2010).

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
    • Lesica, P., P. Husby, and S. V. Cooper. 1998. Noteworthy collections: Montana. Madrono 45:328-330.
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Citation for data on this website:
Gray Aster — Eurybia glauca.  Montana Field Guide.  .  Retrieved on , from