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Ram's-head Lady's-slipper (Cypripedium arietinum)

Life history

Species overview

Ram's-head Lady's-slipper (Cypripedium arietinum), a Wisconsin Threatened plant, is found in two different habitats: cool, dense, calcareous conifer swamps and cool, sandy margins of conifer forests, boreal forests, and dunes. Blooming occurs late May through early June; fruiting occurs late June through late July. The optimal identification period for this species is late May through early June.

Synonyms: Criosanthes arietina


  • Distinguishing characteristics: Cypripedium arietinum may be distinguished from other members of the genus by the arrangement of leaves, which are spiraled rather than 2-ranked. The flower head is quite distinctive and cannot be confused with any other species.
  • Flower characteristics: Flower solitary with a strongly reddish-purple veined, 1.5 to 2.5 cm long pouch with a white lip; lateral sepals thin, linear, greenish-brown, separated to base; dorsal sepal 12 to 25 mm long and 5 to 13 mm wide.
  • Fruit characteristics: Capsule with tiny seeds.
  • Leaf characteristics: Leaves 3 to 5, spiraled around stem, sessile, 5 to 10 cm long, lance-shaped to elliptic, may be finely pubescent, occasionally folded.


  • Blooming phenology: late May through early June
  • Fruiting phenology: late June through late July
  • Optimum time to identify: The optimal identification period for this species is late May through early June


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Thuja occidentalis, Abies balsamea, Picea glauca, Betula papyrifera, Shepherdia canadensis, Cypripedium parviflorum, C. reginae, Coptis trifolia, Cornus canadensis, Carex eburnea.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Ram's-head Lady's-slipper (Cypripedium arietinum). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Cypripedium arietinum in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusTHR
Federal Status in Wisconsinnone
State RankS2
Global RankG3
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found in two different habitats: cool, dense, calcareous conifer swamps and cool, sandy margins of conifer forests, boreal forests, and dunes.
  • Soils: Cool subacid to neutral soils.

Natural communities

This table lists the natural communities that are associated with Ram's-head Lady's-slipper. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Ecological landscapes

This table lists the ecological landscape association scores for Ram's-head Lady's-slipper. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • Avoid broadcast spraying of herbicides; use care with spot spraying.
  • Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.
  • Avoid locating landings, staging areas, or access routes on or near known populations.
  • Avoid site preparation that heavily disturbs herbaceous ground layer and soil; these include bulldozing and furrowing, as well as grubbing and stump removal.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • Avoid rapid and dramatic reductions in canopy cover or basal area in wet areas to reduce risk of swamping.
  • Although maintaining high overall forest canopy is important, silvicultural techniques which open small gaps in the canopy may be beneficial to this species.
  • Minimize disturbance to hydrology, including soil disturbance from rutting.
  • Buffer management around unique microhabitats such as ephemeral ponds, seeps, etc.


Ram's-head Lady's-slipper Photo.

Photo © M. Jaunzems.

Ram's-head Lady's-slipper Photo.

Photo by Thomas Meyer, Wisconsin DNR.

Ram's-head Lady's-slipper Photo.

Photo © F. G. Irwin.

Ram's-head Lady's-slipper Photo.

Photo by Kevin Doyle, Wisconsin DNR.

Ram's-head Lady's-slipper Photo.

Photo © M. Jaunzems.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition