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Collins' Rockcress - Boechera collinsii
Arabis holboellii var. collinsii
(see State Rank Reason below)
State Rank Reason (see State Rank above)
Originally reported for Montana by Windham (FNA), though subsequent information discounts this report (Lescia 2012).
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.
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."
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:
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(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
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- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
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