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).
Stems stout, floating to erect, 2-6 dm; lvs flat or weakly keeled, 3-8 mm wide, the bracteal ones much dilated at base, infl usually simple, occasionally with a basal branch; pistillate heads several, closely glomerate, sessile, 1.5-2 cm thick when ripe; tep linear-oblong, reaching just beyond the middle of the fr, attached at or near the base of the short stipe; achene brown, shining, the body fusiform, 3-4 mm, slightly constricted below the middle, tapering to a straight or slightly curved beak 1.5-2 mm; staminate head 1(2), contiguous with the upper pistillate head; 2n=30. Bogs and shallow water; interruptedly circumboreal, reaching our range in N. Minn.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.