Carex nigromarginata

Cusick (1992) describes Carex nigromarginata as "a beautiful sedge with brightly-colored scales of rich chestnut or purple with a green midrib".

The plants are perennial herbs, 4-12 in. tall, growing in dense tufts, often producing short branches which root. Each stem produces a single inflorescence. Principal leaf blades are very narrow. The flowers are unisexual. Staminate flowers occur on the end of the elongated flower structure, the pistillate below. Staminate flowers contain three small, slender, erect stamens which project beyond the petals when pollen is produced. There are 1-4 pistillate flowers (usually 2 or 3) up to .25 in. long, stemless, often crowded, and the lowest sometimes slightly separated but overlapping the next above. The small dry fruit does not open at maturity, is three-angled or nearly round, and contains 3 stigmas. (derived from Gleason 1952).

Carex nigromarginata is a distinct taxon. The plant remains mostly uniform in character and habitat throughout its range (Cusick 1994); however, the relative length of culm and blades, the shape and coloration of pistillate scales, the shape of staminate scales, and the size of the perigynia are variable. This has lead to the fabrication of varieties, subspecies, and species according to some authors (Gleason 1952).

Carex nigromarginata is a member of the section Montanae (Kunth) [Acrocystis Dumort.] and can be separated from similar species of this section in North America by the following characteristics: "The culms are shorter than the stiff blades and of varying lengths but concentrations of peduncled pistillate spikes at the very base of the plant are lacking; the leaf sheaths are strongly fibrillose with age and the plants are cespitose, without elongate stolons; the perigynia are quite large, mostly 3-4 mm in length with the body definitely longer than wide and are more or less concealed by dark purplish-margined scales approximately equal to the perigynia in length" (Reznicek and Catling 1982). In addition, the plant is a clump-former with no elongate rhizomes. It is a very earlier bloomer (Reznicek 1994).

Carex nigromarginata is also very similar to C. umbellata and C. abdita because of its partially hidden spikelets and its persistent and often tattered leaves. C. nigromarginata is distinguished by its much narrower perigynia (Mohlenbrock et al. 1962).

Carex nigromarginata is thought to be a species of fire systems. It tends to occur in stable, resistant populations although the habitat and soil conditions are somewhat limited globally (Reznicek 1994). It is found on dry to mesic, acidic, sandy, or rocky substrates in deciduous (commonly oak/oak-hickory) woods edges, openings, oak savannas, road banks, etc., in the eastern United States. Less commonly, it is found associated with open coniferous habitats. Other dry woodland sedges, also of the section Montanae, are typically found with C. nigromarginata (Reznicek 1994). It is locally abundant in light gaps such as those created by windfalls and is easily established on patches of bare soil. Along the southern end of its range in the Appalachians, the habitat amplitude increases to include more mesophytic sites in deciduous forests, commonly on steep slopes where the soil is naturally disturbed by erosion and light is better able to reach the forest floor. In these situations, C. nigromarginata is the predominant understory species. Along the western end of its range, it is more likely to be found in forest openings with a fair amount of graminoids. (Cusick 1994, Reznicek 1994).

Habitat types are listed per state below. The information is accurate; however, it may not be comprehensive:

In Alabama, Carex nigromarginata is confined to the unglaciated Appalachian Plateau. It is locally common in oak-pine woods and on the tops of sandstone exposures (Cusick 1992). One collection was on a north-south ravine of sandy loam with Quercus alba, Liquidambar spp., Pinus spp., and Cornus florida (University of Michigan Herbarium).

In Arkansas, J. H. Rettig made collections in 1986 from habitats including: dry, sandy soil and partial shade in sandhill vegetation of Quercus incana, Q. stellata and Pinus spp.; rocky slopes and shade above a river and road with Carpinus caroliniana, Pinus spp. and Cornus florida; and in a sandstone area with Pinus echinata, Quercus alba and Carya spp. A collection was also made in mesic slope habitat below a cliff in shale and sandstone soils with Quercus alba, Acer saccharinum, and Hamamelis sp. (University of Michigan Herbarium).

In Connecticut, a 1901 historic collection was made on Lantern Hill, New London County "among rocks." This occurrence has not been relocated (Connecticut Natural Diversity Database 1994).

In Georgia, C. nigromarginata is generally found in dry rocky woods in partial shade (Allison 1994). Notes from collections that have been made include: a rocky woods near the summit of Graves Mountain, altitude 850 ft. (University of Minnesota Herbarium); on top of a sandstone formation; and in sandy loam soil at the edge of an opening in low woods of Carya, Pinus and Quercus nigra (University of Michigan Herbarium).

In Illinois, Carex nigromarginata occurs on a wooded bluff with a steep slope in the Ozark Hill Prairie Research Natural Area (Illinois Natural Heritage Division 1994). A collection was made on a low, open, west-facing slope underlain with sandstone. This site "was almost certainly a savanna in the past" (University of Michigan Herbarium).

In Kentucky, a collection was made from a rocky slope of a south-facing creek valley in young oak woods (University of Michigan Herbarium).

In Massachusetts, a collection was made on an east-facing mountain slope in a woodland clearing (University of Minnesota Herbarium).

A Mississippi collection was made on the south side of Highway 82 on sandy loam soil with thick leaf litter under mixed hardwoods and pines (University of Michigan Herbarium).

In Missouri, this species has been collected from the Ozarks and from acid soils on wooded sandstone slopes, in crevices on sandstone or chert outcrops, and on gravely wooded soils of Crowley Ridge (Steyermark 1963). It is also known from a site on a steep open hillside in nearly pure sand (Missouri Natural Heritage Database 1994). It is a species of savanna remnants and dry oak forests in openings. New populations are found with some regularity (Ladd 1994, Yatskievych 1994).

In Ohio, the species grows in very dry, well-drained upland white oak/Virginia pine woodlands in acidic (never basic) soil on sandstone ledges and cliffs (Cusick 1994).

A population on Long Point on the north shore of Lake Erie in Norfolk County, Ontario, is the only population confirmed from Canada (Catling 1994, Oldham 1994, Ontario Conservation Data Centre 1994, Reznicek and Catling 1982, Reznicek and Catling 1989). The old dune area is unique to this part of Canada and is strongly influenced by the moderating local climate of the lake. Catling (1994) believes that the most important environmental influence on this population is this climate. The plants are found in two sites. In the first site, they are frequent and locally dominant in the driest areas of sandy knolls in an open Quercus rubra and Acer rubrum woodland (Reznicek and Catling 1982, University of Michigan Herbarium). These areas receive a significant amount of light due to the presence of an open marsh and pools surrounding the small knolls and the absence of shrubs and saplings due to deer browsing. The rooting medium has a pH of 4.6 and includes an upper 2 cm of coarse sand mixed with much organic material. The substrate is almost pure sand at 5 cm depth and has a pH of 5.0. Dominant associates included the mosses Leucobryum albidum, Polytrichum ohioense, and Dicranum scoparium; a sparse cover of vascular plants including Carex artitecta, Danthonia spicata (Poverty Grass), Panicum linearifolium (Panic Grass), and Poa compressa (Canada bluegrass). Also included are Panicum latifolium, P. oligosanthes, Carex muhlenbergii, and C. pensylvanica. The second site is on low dunes in a sandy opening of a Betula papifera forest with lichens and Polytrichum sp. (Reznicek and Catling 1982, University of Michigan Herbarium).

In Pennsylvania, a collection was made on an open logging road in a mixed hardwood forest (University of Michigan Herbarium). It was also collected in dry fields and wooded slopes (University of Minnesota Herbarium).

In South Carolina, a collection was made from a dry, steep hardwood forest above a small stream (University of Michigan Herbarium) and on a bluff in a mixed hardwood forest (University of Minnesota Herbarium).

In Tennessee, collections were made from dry cherty ridgetop forests dominated by Quercus prinus. Two mesic woods locations are also worth noting. (University of Michigan Herbarium).

In Virginia, a collection was made on a north-northwest facing roadbank with Fagus grandifolius, Liriodendron, Quercus falcata, and Liquidambar (University of Michigan Herbarium) and in a dry pine and oak woods.

In West Virginia, a collection was made on a dry, rocky road bank (University of Michigan Herbarium). Other locations include a sandstone cliff; an oak-hemlock slope; a dry rocky road bank; an open, dry woodland area; and a dry ridge top between a meander of Sugar Creek (West Virginia Natural Heritage Program 1992).

In the Great Smoky Mountains National Park, this species is scarce (P1). Although it has been known to occur in rich woods at low elevations, a specimen was collected recently from a post-fire dry woods (Rock 1994). Radford (1968) also describes this as a dry woods species.

Carex nigromarginata does not compete well with other herbaceous species (Gaddy 1994). It is a seed banking species that does well in bare soil and areas where the soil is disturbed, such as on soil tip mounds, ant hills, logging roads, road banks, and burned areas (Reznicek 1994).

Pre-existing and seeded plants tend to be almost weedy in areas with new openings in the canopy (e.g., under new windfalls), then will persist as succession shades them into less productive populations (Gaddy 1994). Phenology: The black-edged sedge is one of the few Carices to produce evergreen or overwintering leaves. Evergreen leaves allow growth to continue in late autumn after tree leaf fall has occurred and prior to leaf flourishing in the spring. Early growth in the spring allows these plants to out-compete neighboring plants by producing large clumps before other vegetation has the chance to begin growth for the year. Flowering and fruiting occur very early for this species. In South Carolina, it flowers in late March and early April and fruits soon after (Gaddy 1986, Gaddy 1994, Radford et al. 1968). In New York, this species flowers through May and fruits in early June (New York Natural Heritage Program 1994).

Dispersal: Carex nigromarginata was demonstrated to be regularly, but perhaps not solely, dispersed by ants in the southern Appalachians of South Carolina (Gaddy 1986). Fresh Carex nigromarginata diaspores were presented to two ant species, Crematogaster lineolata and Prenolepis impairis. In 100% of all encounters with the diaspores, both species of ants transported the diaspores more than ten centimeters. This high rate may be explained by the relatively large white elaiosomes, swellings near the base of the perigynia present on the diaspores. The ants typically move these seeds into disturbed areas such as soil piles caused by treefalls or onto areas where soil sloughs off of tree bases.

Reproduction: A plant can clone outward and sustain a population theoretically "forever" under optimum conditions, eliminated only by a change of habitat. What sometimes appears to be a large population of 20-30 clumps may in reality be a single clone, the central vegetative material simply decayed away over time. The species can produce a seedbank that lasts at least decades and questionably for centuries (Reznicek 1994). It is also evident that sexual reproduction occurs in a population; the tussocks are generally of varying sizes (Cusick 1994). Chromosome number: 2n = 34, n=17 (Smith 1988).