Thick-leaf Whitlow-grass - Draba crassa
State Rank Reason (see State Rank above)
Scattered across southwest Montana where it is known from alpine slopes in several mountain ranges. Overall abundance and distribution is still poorly known, though it is likely to be more common than collections indicate.
- Details on Status Ranking and Review
Score2 - Small: Generally 2,000-10,000 individuals.
CommentEstimated as population levels from specimen collections are largely unknown.
Score1 - Peripheral, Disjunct or Sporadic Distribution in MT: Widespread species that is peripheral, disjunct or sporadically distributed within MT such that it occurs in <5% of the state (<7,500 sq. miles or the combined area of Beaverhead and Ravalli Counties) or is restricted to 4-5 sub-basins.
Area of Occupancy
Score1 - Moderate: Generally occurring in 11-25 Subwatersheds (6th Code HUC’s).
Score1-2 - Moderate to High.
Score0-1 - Stable to Minor Declines:
CommentTrends unknown, though populations are likely stable or experiencing only minor declines.
Score0-1 - Low to Medium.
Score1 - Moderate Vulnerability: Specific biological attributes, unusual life history characteristics or limited reproductive potential makes the species susceptible to extirpation from stochastic events or other adverse impacts to its habitat and slow to recover.
Raw Conservation Status Score
6 to 9 total points scored out of a possible 19.
Perennial from a simple or branched caudex clothed in old leaf bases. Stems simple, 4–12 cm. Basal leaves petiolate, oblanceolate, 2–5 cm long, entire. Stem leaves several, lanceolate, sessile. Vestiture of simple and forked hairs on the stem and sparse cilia on leaf margins. Petals yellow, 3–5 mm long. Fruit ascending, 5–9 × 3–5 mm, glabrous, often twisted; style 0.3–1 mm long; lower pedicels 2–8 mm long (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX
Regional endemic of south-central Montana, western Wyoming, northeastern Utah, and Colorado.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Rocky areas in the alpine particularly on cool, shady sites.
Ecological Systems Associated with this Species
- Commonly Associated with these Ecological Systems
Threats or Limiting Factors
STATE THREAT SCORE REASON
Reported threats to Montana’s populations of Thick-leaf Whitlow-grass include a population expected to decline by at least one-third where invasive weeds have strong negative impacts (MTNHP Threat Assessment 2021).
- 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
Do you know of a citation we're missing?
- Aho, Ken Andrew. 2006. Alpine and Cliff Ecosystems in the North-Central Rocky Mountains. Ph.D. Dissertation. Bozeman, Montana: Montana State University. 343 p.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
- 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.