Vascular Plants of North Carolina
Account for Flat-stem Spikerush - Eleocharis compressa   Sullivant
Members of Cyperaceae:
Members of Eleocharis with account distribution info or public map:
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Section 5 » Family Cyperaceae
AuthorSullivant
DistributionDiscovered in May 2021 bordering a mafic glade in Butner, Granville County, by Eric Ungberg; specimen at NCU.

Ranges from Can. south to northern NC, GA, AL, TX, and NM.
AbundanceVery rare; known only from a single site at Butner. The website editors recommend a State Rank of S1 and Significantly Rare status.
HabitatMoist margin of mafic cedar glade, over diabase: "damp thin soil near exposed rock with mosses, Isoetes piedmontana, Packera sp." Elsewhere in range it occurs in glades, barrens, etc., usually where some ponding or moisture on the surface.
PhenologyThe May 16, 2021 collection was flowering. It is important to obtain mature fruits as well.
IdentificationCompared with E. tenuis, the stems and leaves are much wider, and in life essentially compressed. In addition, the rhizome is 2-3 mm thick vs. 1.5 mm maximum in that species. Bruce Sorrie carefully checked the specimen against other possibilities in June 2021 and agrees with the ID. It matched annotated specimens from Ont., IL, and WI.
Taxonomic CommentsThe genus Eleocharis, the spikerushes, are unusual members of the sedge family in that the culms (flowering stems) are round or oval (rarely triangular) in cross-section, rather than triangular in the great majority of our sedges. In addition, leaf blades are absent; just 1-2 basal sheaths are present at the base of the culm. There is a single, cylindrical or narrowly ovoid, spikelet of florets at the culm summit. Details of achene (seed) shape, color, ornamentation, bristle length, and beak (tubercle) shape and size, are critical ID factors.
Other Common Name(s)Flattened Spikerush, Flatstem Spikerush
State Rank[S1]
Global RankG4
State Status[SR-P]
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