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Montana Field Guide

Montana Field Guides

Graham's Rockcress - Boechera grahamii
Other Names:  Arabis confinis var. brachycarpa, Arabis boivinii, Arabis holboellii var. brachycarpa

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Native Species

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

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Reported for Montana in Flora of North America.
General Description
Biennials or perennials; caudex present or absent. Stems usually 1 per caudex branch, arising from center of rosette near ground surface, (1.2-) 2-12 dm, glabrous or pubescent proximally, hairs (trichomes) simple and sessile or subsessile, 2 or 3(-6)-rayed, to 1 mm, glabrous distally. Basal leaves: blade oblanceolate, 1.5-10(-20) mm wide, margins entire or dentate, ciliate proximally, hairs (simple) to 1 mm, surfaces sparsely to densely pubescent, hairs sessile or subsessile, 2-4(-7)-rayed, 0.2-0.6 mm. Cauline leaves: (10-)13-52, often concealing stem proximally; blade auricles 1-5 mm, surfaces of distalmost leaves glabrous. Racemes 16-88-flowered, usually unbranched. Fruiting pedicels divaricate-ascending to descending, usually gently curved downward, rarely straight, 5-22(-30) mm, glabrous. Flowers divaricate; sepals glabrous or pubescent; petals usually white, rarely lavender, 5.5-8 × 1-2 mm, glabrous. Fruits divaricate-ascending to pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 3.5-9 cm × 1-1.8 mm; valves glabrous; style up to 0.5 mm. Seeds uniseriate to sub-biseriate, 1-1.8 × 0.8-1.2 mm; wing continuous, 0.1-0.25 mm wide (modified from Al-Shehbaz and Windham, 2010, Fl. North America, Vol. 7).

Flowering occurs from May to August.

Range Comments
From AK across much of Canada south to WA, CO, and many upper midwest and northeastern states (Kartesz 2009). The absence of reports from UT, ID, AZ, and NM seem suspect but may reflect changing generic and specific boundaries and a normal taxonomic lag period for updating determinations in herbaria.

Observations in Montana Natural Heritage Program Database
Number of Observations: 26

(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 slopes and sandy soil in prairies and open forests; 100-3200 m" (Al-Shehbaz and Windham 2010).

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Citation for data on this website:
Graham's Rockcress — Boechera grahamii.  Montana Field Guide.  .  Retrieved on , from