Clustered Bur-reed

Sparganium glomeratum, the clustered bur-reed, is a species of bur-reed. It is a water plant native to high elevation lakes and marshes of Europe, Asia, and North America. North American populations were doubted as introduced due to its scarce and scattered populations, but a recent herbarium survey found more localities of the species in the central of Canada, concluding the species as circumpolar species.

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.