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Montana Field Guides

Lyall's Rockcress - Boechera lyallii
Other Names:  Arabis lyallii

Native Species

Global Rank: G5
State Rank: S4
(see State Rank Reason below)

Agency Status


External Links

State Rank Reason (see State Rank above)
Boechera lyallii occurs in higher elevations throughout most mountain ranges in western Montana. Based on numerous herbarium specimen data, occurrences appear stable except in Lincoln County where data is old. Threats have not been identified, and current information on population sizes and locations is needed.
  • Details on Status Ranking and Review
    Lyall's Rockcress (Boechera lyallii) Conservation Status Review
    Review Date = 06/28/2018
    View State Conservation Rank Criteria
    Range Extent

    ScoreF - 20,000-200,000 sq km (~8,000-80,000 sq mi)

    Area of Occupancy

    ScoreE - 26-125 4-km2 grid cells

    Number of Populations

    ScoreD - 81 - 300

    Number of Occurrences or Percent Area with Good Viability / Ecological Integrity

    ScoreD - Some (13-40) occurrences with excellent or good viability or ecological integrity

    Environmental Specificity

    ScoreC - Moderate. Generalist or community with some key requirements scarce


    ScoreD - Low

    CommentNo known threats.

General Description
PLANTS: Long-lived perennial that grows from a simple or branched, woody caudex (FNA 2010). Usually one stem grows from the center of a rosette (FNA 2010). Stems are 3–20 cm (FNA 2010).

LEAVES: Basal leaves are linear-oblanceolate, 1-5(-8) mm wide and 1–3 cm long, and fleshy with entire margins (FNA 2010, Lesica et al. 2012). Stem leaves are lanceolate to ovate, auriculate or not. Vestiture of sparse, simple to branched hairs on basal leaves or plants glabrous (Lesica et al. 2012).

INFLORESCENCE: Unbranched racemes of 2-10(-15) purple flowers (FNA 2010).

Flowering June to August (FNA 2010).

Range Comments
British Columbia and Yukon in Canada. California, Idaho, Montana, Nevada, Oregon, Utah, and Washington in U.S. (FNA 2010).

Observations in Montana Natural Heritage Program Database
Number of Observations: 134

(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)

Stony soil and cobble of fellfields, moraine; subalpine, alpine, often in areas of late snow release (Lesica et al. 2012). Cliffs, talus slopes, gravelly soil in alpine and subalpine habitats from 1,400 to 3,700 meters (FNA 2010).

Reproductive Characteristics
Flowers: Lavender to purple petals of 6–10 mm length and glabrous (FNA 2010, Lesica et al. 2012). Fruits ascending to erect, 2–5 cm × 2–3 mm; seeds wing-margined, in 1 or 2 rows per locule (Lesica et al. 2012).

  • Literature Cited AboveLegend:   View Online Publication
    • Flora of North America Editorial Committee, eds. 2010. Flora of North America North of Mexico. Volume 7. Magnoliophyta: Salicaceae to Brassicaceae. Oxford University Press, Inc., NY. 832 pp.
    • 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?
    • Aho, Ken Andrew. 2006. Alpine and Cliff Ecosystems in the North-Central Rocky Mountains. Ph.D. Dissertation. Bozeman, Montana: Montana State University. 343 p.
    • Ament, R.J. 1995. Pioneer Plant Communities Five Years After the 1988 Yellowstone Fires. M.Sc. Thesis. Bozeman, MT: Montana State University. 216 p.
    • Hawkins, P.H. 1903. The alpine flora of Montana. M.Sc. Thesis, Bozeman, MT: Montana State University. 24 pp.
    • Jones, W. W. 1901. Preliminary flora of Gallatin County. M.S. Thesis. Bozeman, MT: Montana State College. 78 pp.
    • 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.
    • Martin, S.A. 1985. Ecology of the Rock Creek bighorn sheep herd, Beartooth Mountains, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 152 p.
    • Simanonok, M. 2018. Plant-pollinator network assembly after wildfire. Ph.D. Dissertation. Bozeman, MT: Montana State University. 123 p.
    • Williams, K.L. 2012. Classification of the grasslands, shrublands, woodlands, forests and alpine vegetation associations of the Custer National Forest portion of the Beartooth Mountains in southcentral Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 376 p.
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Citation for data on this website:
Lyall's Rockcress — Boechera lyallii.  Montana Field Guide.  .  Retrieved on , from