4. Sparganium glomeratum (Laestadius) Beurling, Årsberätt. Bot. Arbeten Upptäckter. 1852: 221. 1857.
Sparganium erectum var. glomeratum Laestadius, Årsberätt. Bot. Arbeten Upptäckter 1850(bihang 2): 2. 1853
Plants slender to robust, to 0.4(--0.6) m; at least some leaves and inflorescences emergent, erect. Leaves stiff, weakly keeled, to 50 cm 6 mm. Inflorescences: rachis unbranched, condensed, erect; bracts ascending, somewhat inflated near base; pistillate heads 2--6, mostly supra-axillary, sometimes opposite bract above, upper crowded, sessile, proximal head not contiguous with upperdistal, peduncled, 1.2--1.6(--2) cm diam. and contiguous in fruit; staminate heads 1(--2), contiguous or not with distalmost pistillate head. Flowers: tepals without subapical dark spot, entire to erose; stigma 1, lanceolate. Fruits greenish brown, lustrous, stipitate, fusiform, body not faceted, slightly constricted near equator, 3--6 2--3 mm, tapering to beak; beak straight, 1.5--2 mm; tepals attached at base, reaching 1/3 to 1/2 length of fruit. Seeds 1. 2n = 30.
Flowering summer (Jul--Aug). ; Sshallow, quiet, neutral, mesotrophic waters; 0--1000 m; Alta., B.C., Nfld. and Labr. (Labr.), Ont., Que., Sask.; Minn., Wis.; circumboreal.
Sparganium glomeratum is apparently rare, or perhaps is only rarely collected, in North America, except it is locally common in sedge-marshes and black-ash swamps near the western end of Lake Superior. The species is rather invariable throughout its circumboreal range (C. D. K. Cook and M. S. Nicholls 1986).