Sparrow's-egg Lady's-slipper - Cypripedium passerinum
State Rank Reason (see State Rank above)
Sparrow's-egg lady's-slipper is known from over a dozen moderate to large-sized populations, a few dozen small occurrences and one historical location. Several of the occurrences are either in designated wilderness areas or in Glacier National Park. The main threat to populations appears to be from potential hydrologic changes.
- Details on Status Ranking and Review
Score2 - Small: Generally 2,000-10,000 individuals.
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.
Score0-2 - Stable to Moderate Declines:
CommentTrend data are largely unavailable. Habitat generally appears to be stable and it does not appear likely that severe declines have occurred, though it is possible that minor or moderate declines have occurred or may be occuring across the species' range in Montana.
Score1-2 - Medium to High.
CommentThough impacts may be occurring or likely at some locations, the magnitude or immediacy of threats to the species or its habitat do not appear to be severe.
Score2 - High Vulnerability: Very specific biological attributes, unusual life history characteristics or limited reproductive potential makes the species highly susceptible to extirpation from stochastic events or other adverse impacts to its habitat and very slow to recover.
Raw Conservation Status Score
8 to 12 total points scored out of a possible 19.
Sparrow's-egg Lady's-slipper is a perennial with leafy stems reaching up to 35 cm high and arising from slender, creeping rhizomes. The 3-5 broadly lance-shaped leaves reach up to 15 cm long and clasp the stem; the herbage is covered with long, soft hairs and is usually somewhat sticky. The one or two flowers are subtended by a leafy bract which is longer than the inflorescence. The sepals are green and 10-16 mm long, and the upper is longer than the lower two. The petals are white; the lower is pouch-like with purple spots on the inside, and the other two resemble the sepals but are shorter. The erect capsule is ovoid and bears thousands of tiny seeds.
Flowering in late June-early August.
This species can be distinguished from our other white lady's slipper (C. montanum) by the sepals that are shorter than the slipper-like petal and not wavy or twisted.
AK and Yukon to Hudson Bay and Quebec, south to southeastern BC, northern MT, and to the region of Lake Superior. Peripheral.
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)
Mossy, moist, or seepy places in coniferous forests, often on calcareous substrates.
Ecological Systems Associated with this Species
- Additional ReferencesLegend: View Online Publication
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- Arditti, J., J.D. Michaud and P.L. Healey. 1979. Morphometry of orchid seeds. I. Paphiopedilum and native California and related species of Cypripedium. American Journal of Botany 66(10):1128-1137.
- Catling, P. M. 1983. Autogamy in eastern Canadian Orchidaceae: a review of current knowledge and some new observations. Naturaliste Canada 110:37-53.
- Hoitsma, T. 1992. Sensitive Plant Survey, Fortine Ranger District, Kootenai National Forest. [Unpublished Report] 65 pp. plus appendices.
- Horn, G. 1980. Report on inventory of threatened or endangered, rare, or sensitive plants-Headwaters Resource Area, Butte District, Bureau of Land Management, Montana. Unpublished report. 54 pp.
- Keddy, C.J., Keddy, P.A. and R.J. Planck. 1983. An ecological study of Cypripedium passerinum Rich. (sparrow's egg lady-slipper, Orchidaceae) on the north shore of Lake Superior. Canadian Field-Naturalist 97(3):268-274.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Linden, B. 1980. Aseptic germination of seeds of northern terrestrial orchids. Ann. Bot. Fennici 17:174-182.
- Shelly, J.S. 1988. Status review of Cypripedium passerinum, U.S. Forest Service, Region 1, Flathead and Lewis and Clark National Forests. Unpublished report. Montana Natural Heritage Program, Helena, MT 52 pp.
- St-Arnaud, M. and D. Barabe. 1989. Comparative analysis of the flower vascularization of some Cypripedium species (Orchidaceae). Lindleyana 4(3):146-153.
- Vanderhorst, J.P. 1996. Status report on sensitive lady's slipper orchids (Cypripedium calceolus var. parviflorum and Cypripedium passerinum) on the Kootenai National Forest. Unpublished report to the Kootenai National Forest. Montana Natural Heritage Program, Helena, MT 27 pp. plus appendices.