- Scientific name: Cypripedium arietinum
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Endangered (MA Endangered Species Act)
Description
Ram’s head lady’s-slipper is asmall but striking purplish orchid (family Orchidaceae) that is quite rare throughout its range (i.e. globally rare). Plants grow singly or in loose clusters from short rhizomes with long fibrous roots. This slender lady’s-slipper varies in height from 5 to 30 cm (2-12 in). Plants bear 3 to 5 bluish green, elliptic-lance shaped leaves growing along the stem in a spiral arrangement. A small solitary flower is borne at the tip of the stem; plants very rarely bear two flowers. The sac-like lip petal of the flower is white above and streaked below with a net-like pattern of purple, crimson, and sometimes green. The lip petal resembles a miniature charging ram’s head due to its downward-pointing conical shape. The opening of the lip petal is densely covered with long silky hairs. The flower has three distinct brownish purple and green streaked sepals. The dorsal sepal forms an arching hood above the inflated lip. The two lateral petals and sepals twist and spiral downward and away from the inflated lip.
Ram’s head lady’s-slipper often reproduces vegetatively by offshoots from parent plants. Sexual reproduction is less common. Plants are obligate out-breeders and require pollination by small bees to accomplish cross-pollination. Although this plant is not a nectar producer, bees are attracted by the sweet-smelling vanilla-like odor and the venation pattern on the flower. Upon successful pollination, many microscopic seeds are produced and contained within a linear-ellipsoid shaped fruiting capsule.
The height of ram’s head lady’s-slipper is variable; flowering plants are usually 10-15 cm (4-6 in) taller than vegetative plants. The stem is covered by tiny glandular hairs and the leaves are smooth with fine short hairs along their wavy margins. Leaves are 5-10 cm (2-4 in) long, 1.5-3.5 cm (0.6-1.4 in) wide, and sometimes folded lengthwise. The lip petal or flower sac is 1.3-2.5 cm (0.5-1 in) long and 1-2 cm (0.4-0.8 in) wide. Sepals are distinctly free to their base. The dorsal sepal is 1.5-2.5 cm (0.6-1 in) long and 1-2 cm (0.4-0.8 in) wide and forms a hood over the lip; upon pollination, it will droop, covering the opening to the lip petal. Sepals and petals are linear-lanceolate and similar in appearance. The two lateral sepals are 1.5-2 cm (0.6-0.8 in) long and 0.2-0.5 cm (0.08-0.2 in) wide. The lateral petals are the same length but 0.1-0.2 cm (0.04-0.08 in) wide.
Ram’s head lady’s-slipper is easily distinguished from other lady’s-slippers when in flower. Vegetative plants are sometimes confused with yellow lady’s-slipper (Cypripedium parviflorum) or helleborine orchid (Epipactis helleborine).
Life cycle and behavior
Ram’s head lady’s-slipper flowers in mid-spring; fruit matures midsummer and seed dispersal may occur in autumn, and continue in the spring and summer of the following year.
Population status
Ram’s head lady’s-slipper is listed under the Massachusetts Endangered Species Act as Endangered. All species listed are protected from killing, collecting, possessing, or sale and from activities that would destroy habitat and thus directly or indirectly cause mortality or disrupt critical behaviors. The MassWildlife’s Natural Heritage & Endangered Species Program database has 6 records from 4 counties: Berkshire, Franklin, Hampden, and Hampshire. Two of these records have been observed within the last 25 years.
Distribution and abundance
Ram’s head lady’s-slipper is native to east central North America. Its range extends from Nova Scotia, Southern Quebec, Maine west to Saskatchewan, and south to New England, New York, Michigan, Wisconsin, and Minnesota.
Distribution in Massachusetts
1999-2024
Based on records in the Natural Heritage Database
Habitat
Though known in other regions from coniferous swamps and limey coniferous woodlands, ram’s head lady’s-slipper in Massachusetts inhabits somewhat rich, partially shaded conifer and mixed hardwood forests. It prefers seasonally moist circumneutral soils and requires a specialized mycelia fungal structure in the soil for successful germination and uptake of nutrients in the proto-corm and rhizomatous stages of growth. It is often found in microhabitats with little competition from other understory plants.
Sugar maple (Acer saccharum), white ash (Fraxinus americana), basswood (Tilia americana), black birch (Betula lenta), eastern hemlock (Tsuga canadensis) and white oak (Quercus alba) are characteristic trees in the forest canopy. Witch hazel (Hamamelis virginiana) is often scattered in the shrub layer. Herbaceous cover is sparse and may include christmas fern (Polystichum acrostichoides), bashful bulrush (Trichophorum planifolium), white wood aster (Eurybia divaricata), blunt-lobed hepatica (Anemone americana), Canada mayflower (Maianthemum canadense), and Solomon’s seal (Polygonatum pubescens). The introduced helleborine orchid is sometimes found nearby.
Healthy habitats are vital for supporting native wildlife and plants. Explore habitats and learn about conservation and restoration in Massachusetts.
Threats
Ram’s head lady’s-slipper is an exceptionally rare and striking orchid, making it vulnerable to illegal collection by orchid enthusiasts, or picking by the unaware and curious observer. It is also vulnerable to white-tailed deer browse, especially in areas with an over-abundance of deer. This species has a very long life cycle, taking many years to grow from seed to mature fruiting plant. Therefore, the impacts of collection or over-browsing by white-tailed deer have the potential to decimate small populations. Known habitats are susceptible to invasions by non-native plants such as Japanese barberry (Berberis thunbergii) that compete with native plants for space, light, and nutrients. Large-scale land clearing is unlikely at known sites, but this orchid may be sensitive to low levels of habitat and land use change partly due to the specialized relationship it has with soil mycorrhizae. Changes in forestry practices, hydrology, colluvial soil building processes, and fire regimes all have the potential to adversely impact environmental conditions necessary to sustain ram’s head lady’s-slipper.
Conservation
Monitor known populations of ram’s head lady’s-slipper to gain a better understanding of population dynamics, environmental processes necessary to sustain populations, and current threats. Minimize white-tailed deer browse by managing local deer populations, and erecting deer enclosures as needed. Monitor and control invasive species such as Japanese barberry. Consider selective tree removal to maintain or create small canopy gaps. Avoid trampling and prohibit use of off-road vehicles at sites. Conduct research aimed at understanding the factors necessary to maintain the presence and vitality of beneficial mycorrhizae in the soil.
References
Blaney, S. and D. Mazerolle. 2007. Nova Scotia Provincial Status Report on ram’s head lady’s-slipper (Cypripedium arietinum R.Br.). Prepared for the Nova Scotia Species at Risk Working Group. 31 pp.
Brzeskiewicz, M. 2000. Conservation assessment for cypripedium arietinum (ram’s head lady’s-slipper). USDA Forest Service, Eastern Region. Chequamegon-Nicolet National Forest. 20 pp.
Sheviak, C.J. 2003. Cypripedium arietinum in Flora of North America. Vol.26 (Flora of North America Editorial Committee, eds.). Oxford University Press, New York, New York.
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| Date published: | April 15, 2025 |
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