Rare Species Guide

  Synonyms

Carex scirpiformis, Carex scirpoidea var. scirpiformis

  Basis for Listing

Carex scirpoidea is a typical sedge of mesic and wet-mesic prairies in northwestern Minnesota. Prior to settlement, prairie was the predominant native community in that part of the state, and C. scirpoidea was probably common and widespread. Today, C. scirpoidea is found in a select few high-quality prairie remnants that were, for one reason or another, spared the plow when large-scale agriculture changed the landscape of that region beginning over 100 years ago. Carex scirpoidea was listed as a special concern species in Minnesota in 1984.

Interestingly, a singular occurrence of C. scirpoidea was discovered at a site in Lake County in 2000, where there are no prairie soils, no prairie vegetation, and nothing a biologist would consider a prairie habitat. It was found on the unforested portion of a north-facing 46 m (150 ft.) tall cliff, specifically on mossy ledges and in rocky crevices. The population is reportedly well established on the cliff and considered to be a long-term native resident at the site, not a recent arrival. A possible explanation for this unexpected occurrence, which has not yet been thoroughly researched, can be found in the rather complex taxonomic history of this species. There are currently 3 accepted subspecies of C. scirpoidea in North America (Dunlop 2002). The plants in northwestern Minnesota are considered to belong to subspecies scirpoidea, a widespread prairie plant. It is possible that the plants in Lake County belong to subspecies convoluta, a rare subspecies that is geographically centered in the western Great Lakes region.

  Description

Carex scirpoidea is a perennial sedge that grows to a maximum height of about 70 cm (27.6 in.). The stems are reddish purple to brown at the base, somewhat clumped, and they grow from a horizontal rhizome that may reach 4 cm (1.6 in.) in length. The leaves are shorter than the stem, the blades are up to 2.5 mm (0.10 in.) wide, and the ventral portions of the sheaths are hairy. The inflorescence consists of a single, stiff, erect spike 1.5-3 cm (0.6-1.2 in.) long. The spike is unisexual (usually female). The perigynia (the membranous covering of the seed) is densely hairy, elliptical to oblong or obovate in outline, 2.2-2.5 mm (0.09-0.10 in.) long, 1-1.4 mm (0.04-0.06 in.) wide, and abruptly contracted to a short beak. Carex scirpoidea is similar in appearance to C. hallii (Hall's sedge), and the two species may be found growing together, but C. hallii has more than one spike and essentially hairless perigynia.

  Habitat

Carex scirpoidea is typically found in mesic or wet-mesic tall grass prairies. Prominent associated species often include: Andropogon gerardii (big bluestem), Spartina pectinata (prairie cordgrass), Calamagrostis stricta ssp. inexpansa (northern reedgrass), Carex buxbaumii (Buxbaum's sedge), and Juncus arcticus var. balticus (mountain rush). The habitat is sometimes called a wet prairie, although C. scirpoidea does not grow in standing water. In many cases there will be scattered shrubs, particularly Cornus sericea (red-osier dogwood), Salix spp. (willows), or Betula pumila (bog birch). If the shrubs are prominent enough, then the habitat might be called a brush prairie. The general terrain appears essentially flat and level to the eye, although there might be ancient beach ridges within the habitat. The specific habitat inhabited by C. scirpoidea is a subtle zone between upland and wetland. It may appear as a narrow ecotone, or a broad flat basin. The soils are most often heavy black clay, sediment of Glacial Lake Agassiz. Within this general habitat type, C. scirpoidea is usually localized in places where the soils are said to be somewhat saline, although this feature is somewhat difficult to quantify.

  Biology / Life History

Carex scirpoidea is a perennial sedge that grows from a tough, buried rhizome. The flowers are clearly wind-pollinated, like those of most prairie grasses and sedges. Judging from the structure of the seed, short-distance dispersal probably relies on gravity and wind, and the more infrequent long-distance dispersal probably involves an animal vector. Seedling recruitment is probably episodic and may not occur on an annual basis.

The somewhat saline soils that C. scirpoidea seems to prefer are usually more sparsely vegetated than surrounding soils. This may indicate an inability of C. scirpoidea to compete in denser vegetation. The persistence of C. scirpoidea in a region and a habitat where cyclical droughts occur every several years implies it is drought-tolerant. Habitats also may experience season flooding, especially in a spring following a winter with heavier than normal snow cover. This type of dormant-season flooding does not appear to harm C. scirpoidea.

The best time to search for this species is when the seeds are mature, from about the middle of June to early September.

  Conservation / Management

There are reports that C. scirpoidea can survive a certain level of cattle grazing, but just because it may be able to survive grazing does not mean that grazing is appropriate management for this species or its habitat. In fact, livestock grazing creates several problems. It compacts the soil, creates openings for invasive species, tramples plants, and shifts the competitive balance toward more resilient (or unpalatable) species. Carex scirpoidea is found in habitats that have a long history of wildfire, which has kept the habitats free of most woody plants. Unfortunately, most habitats are now highly fragmented and rarely experience wildfire. In cases where fragmented prairie habitats have been acquired for conservation purposes, fire is often reinstated as a management tool with positive results for C. scirpoidea.

  Conservation Efforts in Minnesota

Several habitat fragments that support C. scirpoidea are owned and managed by private conservation organizations and public land management agencies. Some, perhaps most, of these sites are actively managed in some way, although goals and objectives vary. Unfortunately, the full effects of various management activities on C. scirpoidea are not being monitored.

  References and Additional Information

Dunlop, D. A. 2002. Carex sect. Scirpinae. Pages 549-553 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.

Smith, W. R. 2018. Sedges and rushes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 696 pp.