Floating Bur Reed

Foodplant / feeds on
larva of Donacia sparganii feeds on root of Sparganium angustifolium

Sparganium angustifolium is sometimes abundant, its leaves then covering the surface. It is a relatively invariable species that forms fertile hybrids with S. emersum (C. D. K. Cook and M. S. Nicholls 1986), from which it is distinguished by its contiguous staminate heads and flat to plano-convex leaves. See the discussion under S. emersum.

Plants slender, to more than 2 m long; leaves and inflorescences usually floating. Leaves limp, unkeeled, flat to plano-convex, 0.2--0.8(--2.5) m  2--5(--10) mm. Inflorescences: rachis unbranched, flexuous, its fertile part usually erect at water surface; bracts ascending, lower bracts inflated near base; pistillate heads 2--5, at least some supra-axillary, not contiguous, sessile or most proximal peduncled (often prominently so in deeper water), 1--3 cm diam. in fruit; staminate heads (1--)2--4, contiguous and appearing as one elongate head, not contiguous with distalmost pistillate head. Flowers: tepals without subapical dark spot, erose-tipped, stigma 1, lance-ovate. Fruits reddish to brownish, dull, short-stipitate, ellipsoid to fusiform, not faceted, body constricted at equator, 3--7 mm, tapering to beak; beak straight, 1.5--2 mm; tepals attached at base, reaching about to equator. Seeds 1. 2n = 30.

Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Conn., Idaho, Maine, Mass., Mich., Minn., Mont., Nev., N.H., N.Mex., N.Y., Oreg., Utah, Vt., Wash., Wis., Wyo.; circumboreal.

Flowering summer--fall (Jun--Oct southwestward, Jul--Aug northward).

Acid, oligotrophic waters of lakes, ponds, ditches, and streams, usually in shallow waters but to 2.5 m deep; 0--4000m.

Sparganium angustifolium var. multipedunculatum (Morong) Brayshaw; S. emersum Rehmann var. multipedunculatum (Morong) Reveal; S. multipedunculatum (Morong) Rydberg, S. simplex Hudson var. multipedunculatum Morong

Sparganium angustifolium Michx. Fl. Bor. Am. 2 : 189. 1803
Sparganium nalans angustifolium Pursh, Fl. Am. Sept. 34. 1814.
Sparganium. simplex angustifolium Torr. Fl. N. Y. 2 : 249. 1843.
Sparganium natans affi,ne A. Gray, Man. ed. 2. 430. 1856.
Sparganium ajffine Macoun, Cat. Can. PI. 4: 71. 1888. Not 5. affLne Schnizl. 1845.
Sparganium subvaginatum Meinsh. Mel. Biol. Acad. St. Petersb. 13: 390, in part. 1893.
Perennial, with a rootstock, usually somewhat thickened at the base of the stem ; stem slender, in deep water floating, 3-12 dm. long, in shallow water occasionally erect, 2-3 dm. high ; leaves 3-6 dm. long, 3-4 mm. wide, dark-green, cellular-reticulate beneath ; lower bracts 1-2 dm. long, dilated and sometimes slightly scarious-margined below ; the upper bracts short, lanceolate or ovate, 1-2 cm. long ; peduncles usually arcuate-flexuose ; pistillate heads 2-4, the lower 1 or 2 usually on supra-axillary pedicels 1-3 cm. long, the upper distant, in fruit about 1.5 cm. in diameter ; sepals spatulate, short-clawed, erose at the apex, nearly two thirds as long as the achenes ; achenes dirty-brown with reddish-brown
bases, stipitate, beaked, constricted at or above the middle, abruptly contracted above ;
stipe about 1.5mm. long; beak about 2 mm. long ; stigma usually less than 1 mm. long;
staminate heads 1-6, sometimes confluent with each other but distant from the pistillate
ones ; anthers oblong-clavate, 1 mm. long, 3-4 times as long as broad.
Type locality : Canada.
Distribution : Ponds and slow streams, from Newfoundland to Connecticut, Pennsylvania, Colorado, California, and British Columbia.

Sparganium angustifolium is a species of flowering plant in the cat-tail family known by the common names floating bur-reed and narrowleaf bur-reed. It has a circumboreal distribution, occurring throughout the northern latitudes of the Northern Hemisphere. It is an aquatic plant, growing in water up to 2.5 meters deep. Its habitat includes acidic, low-nutrient freshwater bodies such as ponds, lakes, slow-moving streams, and ditches. It can become abundant, practically covering the surface of the water. It is a perennial herb producing a floating stem with long, narrow, flattened leaves which can be quite long, sometimes reaching over two meters. It is monoecious, individual plants bearing both male and female inflorescences. These are spherical, the male inflorescence a ball of stamens and the female inflorescence a ball of developing fruits.