Daggett Rockcress -
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Daggett rockcress is at the northern edge of its range in Montana, where it is known only from the vicinity of the Pryor Mountains and adjacent Bighorn Canyon. Detailed survey information for most occurrences is lacking.
Daggett rockcress is a perennial with several lax or decumbent stems reaching 10-30 cm tall and untoothed, pointed basal leaves that are lance- or narrowly spoon-shaped and about 1.5 cm long. The stem leaves are 5-10 mm long and stalkless, with a pair of small lobes at the base; the lower stem and leaves are usually - though not always - sparsely hairy with large simple and forked hairs. Flowers consist of 4 erect, greenish or purple-tinged sepals, 4 spreading, white to purplish, spatula-shaped petals (4.5-6.5 mm long and 1.5-2 mm wide), 6 stamens, and a single pistil. The long, slender pods (siliques) are 2-4 cm long on stalks that are 4-7 mm and arch downward from the stem, resulting in the siliques hanging from the main stem in a descending or pendulous position. The flattened, round, wingless seeds form one row in each of the 2 capsule chambers (Rollins 1993).
Flowering takes place in May, and fruits mature in June.
Arabis holboellii, A. microphylla, A. sparsiflora and A. lemmonii also have spreading or pendulous fruits, but A. demissa is the only one that has leaves with sparse hair on leaf surfaces and leaf margins that are merely ciliate rather than densely hairy. Montana plants are var. languida
NV to MT south to AZ, UT and CO (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
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)
This rockcress occurs in the foothills of the Pryor Mountains (Lesica et al. 1998) and in the Bighorn Canyon National Recreation Area. It grows in canyon bottoms and on outwash plains with dry, stony soils derived from limestone, often in
Juniperus osteosperma woodland but also in limber pine woodlands and sagebrush steppe. Other prominent species in its habitat include Agropyron spicatum and Ribes cereum.
Ecological Systems Associated with this Species
Like most member of the genus,
Arabis demissa occurs in sites with sparse vegetation, suggesting that it is a poor competitor for light, water, or nutrients.
A. demissa grows in semi-arid grasslands and woodlands that are generally grazed, however grazing is unlikely to have adverse effects because the plants are probably unpalatable and would benefit from reduced competition.
Threats or Limiting Factors
STATE THREAT SCORE REASON Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).
Literature Cited Above
Legend: View Online Publication Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p. Additional References
Legend: View Online Publication Do you know of a citation we're missing? Knight, D. H., G. P. Jones, Y. Akashi, and R. W. Myers. 1987. Vegetation ecology in the Bighorn Canyon National Recreation Area. Unpublished report prepared for the USDI National Park Service and University of Wyoming-National Park Service Research. Lesica, P., P. Husby, and S. V. Cooper. 1998. Noteworthy collections: Montana. Madrono 45:328-330. Rollins, R. C. 1993. The Cruciferae of Continental North America: systematics of the mustard family from the Arctic to Panama. Stanford University Press, Stanford, California. 976 pp.