Scleria triglomerata Michx.
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Basis for Listing
Scleria triglomerata is most abundant in the Atlantic and Gulf coastal regions but ranges as far northwest as Minnesota. This sedge is quite local and often rare in the Midwest and along the northern periphery of its range (Core 1936). This is especially true in Minnesota and adjacent states where the species is currently suffering a decline associated with loss of habitat. Scleria triglomerata was first discovered in Minnesota in 1881 at an unknown location in Hennepin County. There are a few early records from 1925 to 1933 from Anoka County and a single record dated 1943 from Ramsey County. In 1960, one of the Anoka County populations was destroyed by construction and the others were believed to be lost to the expansion of the Twin Cities metropolitan area. For many years, the only known location for S. triglomerata was in the Helen Allison Savanna Scientific and Natural Area and adjacent Cedar Creek Natural History Area (Moore 1973).
Scleria triglomerata is a distinctive member of the sedge family, at least in technical terms. In the field, S. triglomerata can be seen among other sedges and grasses in mid- to late summer when the seeds (achenes) have matured. Seeds are relatively large, 3 mm (0.1 in.), and have a smooth, white, enamel-like surface that can be seen among the scales of the female flower cluster. There are several seeds per spikelet (flower cluster) and 1-3 spikelets located near the end of relatively, long culms. The stems often arch over the leaves. Leaves arise near the base of the plant, not on tall, leafy stems. The base of the stem is strongly triangular in cross-section. Leaves are 4-6 mm (0.16-0.24 in.) wide, finely pleated lengthwise, ('W' in cross-section) with a very fine fringe of hairs on the margins. The combination of the white seeds and 4-6 mm wide leaves will positively identify S. triglomerata. Another useful field characteristic is the thick, knotty, ligneous, forking rhizomes. There is only one other member of the same genus in Minnesota, S. verticillata (whorled nut-rush), and it is also a rare species. Scleria verticillata is very slender however, and occurs only in calcareous fens.
All Minnesota populations of S. triglomerata occur in native sand savannas and sand prairies, often in areas of sand dune formations. They are found in very localized microhabitats at each site, usually in moist soil near wet swales or wet meadows.
Biology / Life History
Scleria triglomerata is a perennial graminoid or grass-like plant. It reproduces only by seed, which are dispersed short distances by gravity and perhaps wind. Like most sedges and grasses, this species does not produce showy flower parts for attracting insect pollinators. Recruitment is slow, so sustaining viable populations seems to rely on maintaining a low mortality rate.
Conservation / Management
Scleria triglomerata appears to be a very persistent plant once established in a favorable setting. At least one population is known to have survived years of drought, spring flooding, and periodic prescribed fires in its savanna environs. Since S. triglomerata seems unable to effectively colonize habitats that have been altered by human activities, the key to its survival in Minnesota is the conservation of high-quality native habitats where it is known to occur. The greatest threats to these habitats are land conversion, road building, and off-highway-vehicles. Favorable management activities may involve mechanical removal of encroaching woody plants and prescribed dormant-season fires.
Conservation Efforts in Minnesota
The Minnesota DNR County Biological Survey has been completed in the likely range of this species in the state. At least 3 of the known populations occur on publicly owned land or on land owned by a private conservation organization. This ensures that the habitats will be protected from commercial or residential development.
Core, E. L. 1936. The American species of Scleria. Brittonia 2:1-105.
Moore, J. W. 1973. A catalogue of the flora of Cedar Creek Natural History Area. Bell Museum of Natural History Occasional Paper 12. 28 pp.