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Montana Field Guides

Collins' Rockcress - Boechera collinsii
Other Names:  Arabis holboellii var. collinsii

Undetermined Origin

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

Agency Status


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State Rank Reason (see State Rank above)
Originally reported for Montana by Windham (FNA), though subsequent information discounts this report (Lescia 2012).
General Description
Perennials. Stems usually 1 per caudex branch, arising from center of rosette near ground surface, (1.5-)2.5-8 dm, densely pubescent proximally, hairs (trichomes) simple and short-stalked, 2-rayed, to 1 mm, sparsely pubescent or glabrous distally. Basal leaves: blade oblanceolate, 1-7 mm wide, margins entire or dentate, ciliate along petiole, trichomes (simple), to 0.7 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 5-8-rayed, 0.15-0.4 mm. Cauline leaves: (8-)15-40, concealing stem proximally; blade auricles 1-3 mm, surfaces of distalmost leaves usually sparsely pubescent. Racemes (15-)30-90-flowered, usually unbranched. Fruiting pedicels reflexed, abruptly recurved at base, otherwise straight, 4-13 mm, glabrous or sparsely pubescent, hairs usually simple. Flowers descending to pendent; sepals pubescent; petals usually white, rarely lavender, 4-6 × 0.8-1.5 mm, glabrous. Fruits strongly reflexed, usually appressed to rachis, rarely somewhat secund, straight, edges parallel, 3.5-6 cm × 0.9-1.5 mm; valves glabrous; style 0.2-0.5 mm. Seeds uniseriate, 1-1.4 × 0.8-1 mm; wing continuous (rarely absent), to 0.1 mm wide (modified from Al-Shehbaz and Windham, 2010, Fl. North America, Vol. 7).

Flowering May and June.

Diagnostic Characteristics
According to Al-Shehbaz and Windham (2010, Fl. North America, Vol.7): "Though often treated as a variety of Arabis (Boechera) holboellii....B. collinsii is easily distinguished from that species by having simple and 2-rayed (versus 4-8-rayed) trichomes proximally on stems, and narrower (0.9-1.5 versus 2-2.5 mm) usually non-secund fruits."

Range Comments
Distributional accounts vary; Kartesz (2009) and Al-Shehbaz and Windham (2010) recognize the species across much of Canada, WA to ND, south to ID, UT (barely), WY and NE.

Observations in Montana Natural Heritage Program Database
Number of Observations: 82

(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)

"Rocky and gravelly hillsides, prairies, open woods, floodplains; 600-1400 m" (Al-Shehbaz and Windham, 2010).

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • 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.
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Citation for data on this website:
Collins' Rockcress — Boechera collinsii.  Montana Field Guide.  .  Retrieved on , from