Rare Species Guide

  Basis for Listing

Like many species that are in need of conservation consideration, Carex media (intermediate sedge) is rare and confined to small and specialized habitats. This is certainly true in Minnesota and adjacent jurisdictions. Populations are not only few in number, they are small; rarely more than a few dozen plants are found at any one place. Minnesota Biological Survey searches of potential habitats in Minnesota have been completed, and it is unlikely that many additional populations of C. media will be found. Only a decade ago, it was assumed that rare plants along the bedrock shoreline of Lake Superior were adequately protected by the remoteness and inaccessibility of their habitat.  Since then, the region has experienced a tremendous residential, recreational, and commercial boom. This has raised new concerns about the conservation needs of shore plants. The small vegetation mats where C. media occurs are very fragile and easily destroyed; for these reasons, Carex media was listed as a species of special concern in 2013.

  Description

The stems are arranged in a clump and rise stiffly to a height of about 50 cm (20 in.). The leaves can be up to 4 mm (0.16 in.) wide and are covered with minute papillae. They originate on the lower ¼ of the stem, with the tips reaching to about the middle of the stem. The terminal spike has female flowers at the top and male flowers at the base (gynecandrous). There are 1-3 closely spaced lateral spikes on each stem; they are entirely female, 0.4-0.9 cm (0.16-0.35 in.) long, and more or less sessile. The scales, which subtend the female flowers, are 1.4-2.0 mm (0.6-0.8 in.) long, 1/2 - 3/4 as long as the associated perigynia; they are uniformly purplish-black. The perigynia are ellipsoid in shape, 2.2-3.0 mm (0.09-0.12 in.) long, and 1.1-1.4 mm (0.04-0.06 in.) wide. They are initially pale green, becoming golden-brown with maturity, and have a papillose surface; the apex is a shallowly bidentate beak, 0.2-0.5 mm (0.008-0.02 in.) long. The achenes are trigonous, and the styles are deciduous (Ball and Reznicek 2002). 

Carex media presents a distinctive appearance: a tiny cluster of 2-4 spikes atop a tall, stiff and nearly leafless stem. The contrasting color of the dark scales and the pale perigynia provide a distinctive visual image, especially in early season. In some ways, it is suggestive of a small C. buxbaumii (Buxbaum’s sedge).  Indeed, where you find C. media you will also likely find C. buxbaumii.

  Habitat

Most Minnesota occurrences of C. media are on the shore rocks of Lake Superior (North Shore Highlands Subsection), more specifically in the peaty vegetation mats that develop in rock crevices and along the margins of small rock pools. It is found in similar moist bedrock habitats inland from Lake Superior in Cook County (Border Lakes Subsection) and along the Kettle River in Pine County (Mille Lacs Uplands Subsection). These inland habitats typically develop where water seeps out from seams and crevices in a cliff, creating a small and unique microhabitat. Based on information from adjacent states, we have learned there is the potential for C. media to be found on algific talus slopes in the southeastern counties (Paleozoic Plateau).

  Biology / Life History

Like all members of the genus Carex (sedges) that occur in Minnesota, this species is a wind-pollinated perennial. It spreads only by seed, not by root suckering or rhizome growth. The seeds have no obvious structural adaptation for dispersal; they probably rely on gravity and secondarily on an animal vector.

  Conservation / Management

The most serious threats to the habitat of C. media in Minnesota include shoreline development, human recreation (trampling), the expanding gull population, and any activity that can alter the sensitive microclimate along Lake Superior.

Although the bedrock substrate of these populations is not directly threatened with destruction, the fragile vegetation mats that support this species are. Avoiding the unintended consequences of human foot traffic on the shore rocks of Lake Superior is probably the simplest and most direct action that can be taken on behalf of C. media in Minnesota. Increasing awareness among local land managers of the fragile nature of shoreline habitats is needed.

  Best Time to Search

The best time to search for C. media is when the perigynia are mature, from mid-June to early August.

  Authors/Revisions

Welby R. Smith (MNDNR), 2018

(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.

Michigan Natural Features Inventory. 2007. Rare Species Explorer [web application]. Michigan Natural Features Inventory, Lansing, Michigan.

Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.

Murray, D. F. 2002. Carex sect. Racemosae. Pages 401-411 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.

NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia.

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

Wisconsin Department of Natural Resources. 2007. Intermediate Sedge (Carex media) factsheet. <http://dnr.wi.gov/topic/endangeredresources/Plants.asp>. Accessed 23 June 2009.