- Scientific name: Carex sterilis
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Threatened (MA Endangered Species Act)
Description
Dioecious sedge (Carex sterilis) is an erect, slender, grass-like perennial in the sedge family (Cyperaceae). Like most members of the Cyperaceae, it lacks showy floral parts. Its stiff culms, or stems, rise in dense clumps from short, horizontal, underground stems. These culms grow to between 1 and 7 dm (1/3 - 2 1/2 ft) in height and are aphyllopodic (with the lowermost leaves reduced to scale-like structures). Leaves are 1-2.5 mm (0.04 - 0.1 in) wide and are rough to the touch on their upper surface. Three to five of these pleated leaves grow from each culm. Dioecious sedge's name comes from its reproductive habits (an individual plant generally has flowers that are only of one sex). Dioecious plants have unisexual flowers in which the male and female flowers are borne on separate plants. Some plants may have a few flowers of the opposite sex; hence, the species is described as "subdioecious" (almost dioecious). Dioecious sedge typically has four stalkless spikes (clusters of much-reduced, stalkless flowers arranged on an unbranched axis). However, its plump, dark reddish-brown perigynia (sac-like membranes that enclose the female reproductive structures) are 2.1-3.8 mm (0.08 - 0.15 in) in length and bidentate (two toothed) at the apex. In addition, the perigynia are thick and spongy at the base.
Inland sedge (Carex interior) often occupies the same habitat as dioecious sedge (i.e., moist to wet calcareous areas) and could be mistaken for it. Nevertheless, the anthers (pollen-bearing parts of the stamens) of dioecious sedge can be quite long, up to 2.2 mm (0.09 in). Those in Inland sedge are smaller, only 0.6-1.4 mm (0.02 - 0.06 in) long. Also, in contrast to the chestnut-colored perigynia of dioecious sedge, the perigynia of Inland sedge are green to tan.
Life cycle and behavior
Dioecious sedge's name comes from its reproductive habits (an individual plant generally has flowers that are only of one sex). Dioecious plants have unisexual flowers in which the male and female flowers are borne on separate plants. Some plants may have a few flowers of the opposite sex; hence, the species is described as "subdioecious" (almost dioecious). Dioecious sedge typically has four stalkless spikes (clusters of much-reduced, stalkless flowers arranged on an unbranched axis). However, its plump, dark reddish-brown perigynia (sac-like membranes that enclose the female reproductive structures) are 2.1-3.8 mm (0.08 - 0.15 in) in length and bidentate (two toothed) at the apex. In addition, the perigynia are thick and spongy at the base.
Population status
Dioecious sedge is currently listed as threatened in Massachusetts. There are five current populations that have been verified as extant since 1999, and four historical station (not recently observed). All of the populations occur only in Berkshire county.
Distribution and abundance
The documented range of dioecious sedge extends from Newfoundland to Saskatchewan and south to Pennsylvania, West Virginia, Tennessee, Illinois and Missouri. Dioecious sedge is considered rare in many states where it occurs. States at the edges of its range are likely to list it as rare or vulnerable; only in the central portion of its range is dioecious sedge common. In New England, It is considered critically imperiled in Vermont, imperiled in Massachusetts, vulnerable in Connecticut and Maine and possibly extirpated from Rhode Island. It is not known from New Hampshire. Reasons for the plant's rarity include its highly restricted habitat and the destruction and alteration of its habitat."
Distribution in Massachusetts
1999-2024
Based on records in the Natural Heritage Database
Habitat
Dioecious sedge is a plant of moist to wet calcareous areas, including fens, shores of calcareous rivers or lake, and calcareous swamps. In Massachusetts, habitats include open portions of calcareous fens (natural communities where cold, calcium-rich, nutrient-poor water seeps to the surface) and a sloping seepage area dioecious sedge. Associated plant species include grass-of-parnassus (Parnassia glauca), shrubby cinquefoil (Dasiphora floribunda), rough-leaved goldenrod (Solidago patula), fen goldenrod (Solidago purshii), brook lobelia (Lobelia kalmii), autumn willow (Salix serissima), yellow sedge (Carex flava), bristle-stalked sedge (Carex leptalea), meadow sedge (Carex granularis) and marsh muhly (Muhlenbergia glomerata).
Healthy habitats are vital for supporting native wildlife and plants. Explore habitats and learn about conservation and restoration in Massachusetts.
Threats
Competition from non-native invasive species can be a threat to dioecious sedge, especially in disturbed habitats. Threats include changes in water quality and quantity and other degradation of habitat. Beaver flooding has the benefit of discouraging woody vegetation and keeping the area open but also can flood out dioecious sedge. All listed species 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.
Conservation
Monitoring and removal of competing vegetation should be considered as a management strategy where appropriate. All active management of rare plant populations (including invasive species removal) is subject to review under the Massachusetts Endangered Species Act and should be planned in close consultation with MassWildlife’s Natural Heritage & Endangered Species Program.
References
NatureServe. 2025. NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. Accessed: 5/22/2025.
USDA, NRCS. 2010. The PLANTS Database (http://plants.usda.gov, 6 December 2010). National Plant Data Center, Baton Rouge, LA 70874-449
Contact
| Date published: | April 9, 2025 |
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