Lemmon's Rockcress - Boechera lemmonii
Arabis lemmonii, Arabis drepanoloba, Boechera drepanoloba, Boechera lemmonii var. drepanoloba
(see State Rank Reason below)
MNPS Threat Rank
State Rank Reason (see State Rank above)
Boechera lemmonii occurs in the higher elevations of most mountain ranges throughout western Montana. Based on numerous herbarium specimen data collected from 1894 through 2008, populations appear stable. Threats have not been identified, though some populations do grow on steep, unstable talus slopes. Arabis (Boechera) lemmonii var. drepanoloba has been documented in Montana at two locations, and is recognized as a distinct species by Al-Shehbaz in Flora of North America, Volume 7. However, the distinguishing characters do not strongly correlate in Montana (Lesica et al. 2012). Until there is further study, this variety is lumped with Boechera lemmonii in the State Rank assessment.
PLANTS: Long-lived perennial that grows from a branched, woody caudex (Lesica et al. 2012). Usually one stem per caudex branch grows from the center of a rosette or sometimes sterile, lateral stems arise (FNA 2010). Stems grow from 4–25 cm (Lesica et al. 2012).
LEAVES: Basal leaves are spatulate to oblanceolate, 5–25 mm long, and with mostly entire margins (Lesica et al. 2012). Basal leaf petioles are ciliate and blades are densely to sparsely pubescent with branched, whitish trichomes (FNA 2010). Stem leaves are lanceolate and weakly auriculate (Lesica et al. 2012). Stem leaf hairs are glabrous or sparsely pubescent (FNA 2010).
INFLORESCENCE: Racemes of 3-12(-17) purple flowers, usually unbranched.
Boechera lemmonii is recognized by the combination of secund fruits, mat-forming habit, purplish petals, and obovate-oblanceolate basal leaves (FNA 2010).
Arabis (Boechera) lemmonii var. drepanoloba is recognized as a distinct species by Al-Shehbaz (FNA 2010). Boechera drepanoloba is an apomictic species that arose through hybridization between Boechera lemmonii and Boechera stricta. However, the characteristics defining Boechera drepanoloba are not well correlated in Montana and is treated as a variety within Boechera lemmonii until further studies are conducted (Lesica et al. 2012).
Alberta, British Columbia, and Yukon in Canada. Alaska, California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, Washington, and Wyoming in U.S.
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)
Stony, sparsely vegetated soil of moraine, talus slopes, ridges, streambanks; montane to alpine (Lesica et al. 2018). Cliffs, talus slopes, and gravelly soil in alpine and subalpine habitats at elevations from 2,100 to 4,400 meters (FNA 2010).
Flowers: Greenish to purple tinged sepals are glabrous to sparsely pubescent. Whitish-purple, purple to lavender petals are 5–7 mm long. Fruits are spreading to pendulous, 2–5 cm × 1–2.5 mm, and mostly secund. Seeds are narrowly winged and in 1 row per locule (Lesica et al. 2012).
Herbarium specimens include both sexual and apomictic (asexual reproduction) plants, and further study is needed to determine if they should represent the same species (FNA 2010).
- 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.