Carex laevivaginata (Kukenth.) Mackenzie
Basis for Listing
Carex laevivaginata (smooth-sheathed sedge) is a robust wetland sedge with wide but scattered distribution in the eastern half of the country. It reaches the northwestern limit of its range in southeastern Minnesota. Although it is more common farther east, it appears to be quite rare in Minnesota and rare or uncommon in adjacent states. The preferred habitat of C. laevivaginata in Minnesota is groundwater seeps in The Blufflands region in the southeastern corner of the state. These habitats are very rare, exceptionally fragile, and susceptible to disruptions in the flow of groundwater, even disruptions that may occur several miles from the habitat. For these reasons, C. laevivaginata was listed as a threatened species in Minnesota in 1996.
Carex laevivaginata has stout tufted stems and, except for the distinctive leaf sheaths, could easily be confused with the common C. stipata var. stipata (awl-fruited sedge). The ventral surface of the leaf sheaths of C. laevivaginata are thickened at the mouth, often cartilaginous, yellowish in color, and are not cross-rugulose. The leaf sheaths of C. stipata var. stipata are cross-rugulose and not thickened at the mouth. Carex laevivaginata also has the following characteristics: a compound inflorescence, perigynia (the structures that appear to be the seed or fruit but are actually bracts enclosing the ovary) that are 4-6 mm (0.2 in.) long, have a bulbous, spongy base, and a long beak that is 1-2 times the length of the body.
Technical Description: Culms cespitose, to 100 cm (39 in.) long, wing-margined, weak, appearing flat in pressed specimens. Rhizomes to about 3 cm (1 in.) long. Leaves to 7 mm (0.3 in.) wide; ventral surface of sheaths smooth, not wrinkled, not spotted with colored dots, thickened at summit with a narrow horizontal band of hardened tissue (sometimes yellowish tinged); basal sheaths disintegrating into pale brown fibers; ligules longer than wide. Inflorescence 2--6 cm (0.8—2.4 in.) long; compound, with a few to several short side branches, especially in lower portion of inflorescence. Spikes numerous, sessile, androgynous; bracts setaceous. Pistillate scales about half the length of the perigynia. Perigynia glabrous, lanceolate, 4.5—6.0 mm (0.18—0.24 in.) long, 1.3--2 mm (0.05--0.08 in.) wide; dorsal surface with distinct continuous veins; ventral surface similar or with only faint or discontinuous veins; base spongy or pulpy, often distended or bulbous at maturity; apex tapered or gradually contracted to an indistinct bidentate serrulate beak 2--3 mm (0.08—0.12 in.) long; beak as long or longer than the body. Achenes biconvex; style deciduous. Maturing early June to early July (Smith 2018).
In the southern and eastern portions of its range, this species grows in swamps and woodland swales, in wet ravines, and along the muddy banks of creeks and rivers (Wheeler 1981). In Minnesota, C. laevivaginata seems to prefer cold, calcareous seepage flows in mature hardwood forests or seepage-fed wet meadows, usually in narrow valleys along upper reaches of trout streams. In this setting, seeps and springs emerge on the valley floor, often at the base of a bluff where the valley has cut through specific bedrock strata. Undisturbed seeps are often represented by low mounds of organic matter (peat), which were formed by the groundwater activity. Seeps that support this species vary from those that have significant flowing water to those where the soil is merely moist. In addition to the immediate seepage zone, plants also occur along the groundwater outflow downstream from larger seeps, and less commonly along the moist banks of a nearby creek. Carex laevivaginata is often associated with Fraxinus nigra (black ash), Caltha palustris (common marsh marigold), the rare Floerkea proserpinacoides (false mermaid), and other Carex (sedge) species, sometimes including C. stipata var. stipata, with which it may be confused.
Biology / Life History
Carex laevivaginata sends up its leaves in early spring at, or just before, the time it sends up fertile culms. Perigynia are shed in mid-summer, but the leaves, with their diagnostic sheaths, are present throughout the growing season.
Conservation / Management
The preferred habitat of C. laevivaginata is groundwater seeps in mature hardwood forests. These very rare and fragile habitats are vulnerable to disruption or diversion of groundwater flow. Disruptions can occur directly within C. laevivaginata habitat or several miles away, but both have the same effect of depriving the habitat of the water it needs. These are wetland habitats that require saturated conditions all year. Habitats have been known to survive short-term livestock grazing, if grazing pressure is light. Cattle seem to avoid the unstable peaty habitats if they can, but grazing is considered incompatible with ecologically responsible long-term management of this habitat type. Populations of C. laevivaginata may survive a very limited amount of timber harvest in the vicinity, but no studies have been done to document how much canopy removal the species can tolerate. The increased light and warming that results from even small openings created in the canopy are considered a potential threat to the stability of its habitat. Increased erosion and soil compaction that accompany heavy equipment use are additional threats. Furthermore, several C. laevivaginata populations have been damaged by unlawful off-road vehicle activity.
Best Time to Search
The best time to search for this species is when Carex laevivaginata is in fruit, from late May through mid-July. When searching for this plant, one should be aware of its close resemblance to the common C. stipata, which may occur in the same habitat.
Conservation Efforts in Minnesota
The Minnesota Biological Survey has been completed in southeast Minnesota. Several C. laevivaginata populations occur on State Forests and state Wildlife Management Areas. However, management plans for these areas must provide for the needs of this rare species and its habitat in order for its populations to persist.
Welby R. Smith (MNDNR), 2023
(Note: all content ©MNDNR)
References and Additional Information
Ball, P. W., and A. A. Reznicek. 2002. Carex. Pages 254-572 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.
Minnesota County Biological Survey. 1994. Natural communities and rare species of Houston County. Minnesota County Biological Survey Biological Report No. 50. Minnesota Department of Natural Resources, St. Paul.
Minnesota County Biological Survey. 1994. Natural communities and rare species of Winona County. Minnesota County Biological Survey Biological Report No. 49. Minnesota Department of Natural Resources. St. Paul.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis. 320 pp.
Rosendahl, C. O., and J. W. Moore. 1947. A new variety of Sedum rosea from southeastern Minnesota and additional notes on the flora of the region. Rhodora 49:197-202.
Smith, W. R. 2018. Sedges and rushes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 696 pp.
Wheeler, G. A. 1981. A study of the genus Carex in Minnesota. Dissertation, University of Minnesota, St. Paul. 501 pp.