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Dense-leaf Draba - Draba densifolia
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Draba densifolia is distributed in the western half of the state in four moderate to large populations, six small occurrences and nine historical or poorly documented occurrences. Occupied habitats are at moderate to high elevation which help to minimize disturbance to some of the populations. However, livestock grazing, invasive weeds and off-road ATV use impact some populations.
Dense-leaf Draba is a mat-forming perennial with leaf rosettes at the ends of numerous rootcrown branches, which are clothed with old leaf bases. The leafless stems are 3-15 mm high and arise from some of the rosettes. The fleshy, narrowly lance-shaped leaves are 2-12 mm long and have a prominent midvein and straight, unbranched hairs on the entire margins but are otherwise mostly glabrous. 3-15 stalked flowers are borne at the tops of the stems. Each flower has 4 separate sepals, 4 separate, yellow petals that are 2-6 mm long, and 4 long and 2 short stamens. The style is 0.5-1.0 mm long. The hairy, egg-shaped capsules are 2-7 mm long and are borne on erect or ascending stalks.
Flowering from May-July, depending on elevation.
There are many similar-appearing, yellow-flowered, mat-forming species of Draba in our area. A technical manual and hand lens or microscope is required for positive identification. This species can be dintinquished from D. oligosperma by the simple hairs. Draba daviesiae also has glabrous leaves, except for simple hairs on the margins, but it has glabrous fruits.
AK to AB south to CA, UT and WY (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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Gravelly, open soil of rocky slopes and exposed ridges in the montane to alpine zones.
Ecological Systems Associated with this Species
Threats or Limiting Factors
STATE THREAT SCORE REASON
Reported threats to Montana's populations of Dense-leaf Draba include impacts from multiple land-use activities as its habitat spans moderate to high elevations (MTNHP Threat Assessment 2021). Populations scattered from grasslands to rocky ridgelines are exposed to livestock grazing and trampling, roads and highways, and recreation-related trampling from hikers, climbers or off-highway vehicle (OHV) users. Encroachment of noxious weeds is reported to threaten some populations, where a risk of chemical herbicide application is also a potential concern.
- Literature Cited AboveLegend: 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 ReferencesLegend: View Online Publication
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- Aho, Ken Andrew. 2006. Alpine and Cliff Ecosystems in the North-Central Rocky Mountains. Ph.D. Dissertation. Bozeman, Montana: Montana State University. 343 p.
- Hawkins, P.H. 1903. The alpine flora of Montana. M.Sc. Thesis, Bozeman, MT: Montana State University. 24 pp.
- Jones, W. W. 1901. Preliminary flora of Gallatin County. M.S. Thesis. Bozeman, MT: Montana State College. 78 pp.
- Martin, S.A. 1985. Ecology of the Rock Creek bighorn sheep herd, Beartooth Mountains, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 152 p.
- Mulligan, G.A. 1976. The genus Draba in Canada and Alaska: key and summary. Canadian Journal of Botany 54:1386-1393.
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