Carex conjuncta Boott
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Basis for Listing
Carex conjuncta is an inhabitant of floodplain forests, and reaches the northern periphery of its range in Minnesota. It seems to be fairly common in the center of its range in Missouri and Illinois, but rare or local in Minnesota and portions of adjacent Wisconsin and northern Iowa. It was discovered in Minnesota in 1976 at a single location in the Cannon River Valley in Rice County. It was later found at a separate but nearby site in 2010 and at a single site in Dodge County in 2006. The Dodge County population could not be found in 2007 and is believed to be very small and perhaps transient. Carex conjuncta was listed as a threatened species in Minnesota in 1984.
Sedges are grass-like, perennial herbs that can be easily identified to the genus Carex by their three-ranked leaves, closed sheaths, and triangular (only occasionally round), mostly solid stems, with terminal inflorescence. Identifying a sedge to species is often difficult and positive identification usually requires mature perigynia (the structure that appears to be the seed or fruit but is actually a bract enclosing the ovary) to be present. Carex conjuncta has numerous spikes forming an interrupted inflorescence; some or all spikes have terminal staminate flowers. Rhizomes are short and the perigynia are strongly compressed. The inner band of the leaf sheath is cross-puckered. Carex conjuncta shares these characteristics only with C. alopecoidea (foxtail sedge) and C. stipata var. stipata (awl-fruited sedge), but is distinguished from them by its ovate perigynia, which has a beak that is nearly as long as the body, and by its whitish scales.
The Minnesota populations occur in mature alluvial forests under a canopy of Ulmus americana (American elm), Juglans nigra (black walnut), and Acer saccharinum (silver maple). This habitat type is usually flooded in the spring and may remain wet or moist throughout the summer. Carex conjuncta occurs along with other rare sedges such as C. davisii (Davis' sedge) and C. grayi (Gray's sedge).
Biology / Life History
Carex conjuncta is a perennial sedge. It is wind-pollinated and reproduces only by seed. Dispersal mechanisms are not known, but it is likely that the perigynia and possibly roots are transported on spring floodwaters.
Conservation / Management
In Minnesota, C. conjuncta is known to occur only in a floodplain forest along a small stretch of the Cannon River and in a similar habitat at a single site along Dodge Center Creek, both in the southeastern corner of the state. Although uncertain, it is believed that this is the only habitat type in which the species might occur in Minnesota. These sites should be monitored to insure that invasive species that might threaten the ecological integrity of the habitats do not become established.
Conservation Efforts in Minnesota
The DNR's Minnesota Biological Survey has been completed within the likely range of the species in the state.
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.
Gilley, C. L. 1946. The Cyperaceae of Iowa. Iowa State College Journal of Science 21:55-151.
Gleason, H. A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. Second Edition. New York Botanical Garden, Bronx, New York. 910 pp.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.
Wheeler, G. A., and G. B. Ownbey. 1984. Annotated List of Minnesota Carices, with phytogeographical and ecological notes. Rhodora 86:151-231.