angustifolium Michaux, Narrow leaf bur-reed
Sparganium eurycarpum Engelm., giant bur-reed
Round bur-like flower heads and strap-like leaves distinguish bur-reeds. Spiny flower heads grow on the sides of flowering stems, that bend at each point of attachment giving them a zigzag appearance. Narrow leaf bur-reed is highly variable with leaves ranging from ribbon-like underwater or floating leaves to stiff emergent leaves. Giant bur-reed is an emergent plant that can grow to over 2 m tall. Other, less common, bur-reeds are also found in Washington.
Leaf: Long, narrow, thick and spongy toward the base, alternately-arranged with parallel veins. Narrow-leafed: submersed, floating, sometimes emergent, 20-80 cm long (occasionally longer), to 1.5 cm wide. Giant: usually emergent, more robust, triangular in cross-section at the base, to 2.5 m long, 0.6-2 cm wide.
Stem: Narrow-leafed: submersed, floating, or emergent to 1 m long; usually not branched. Giant: emergent, 0.5-2.5 m long, with 2 to 5 short branches supporting the flower heads.
Flower: Emergent on slender, round stems. Female flower heads are spiny, round balls that turn from green to brown as they mature. Small male flower heads are located above female heads. Narrow-leafed: 2-4 female flower heads, lower female flower heads usually on short stalks; 2-5 male flower heads. Giant: 1-6 female flower heads, 5-12 male flower heads on stem branches. Blooms July to August.
Fruit: Hard, dry achenes cluster in spiny brown balls. Narrow-leaved: achenes often narrow at middle, 3-5.5 mm long, pointed beak (2 mm). Giant: wedge-shaped achenes, 6-10 mm long, beak 2-4 mm.
Root: Rhizome partially or fully underground.
Propagation: Rhizomes, seeds. Giant: small tubers.
Importance of plant: Excellent food and habitat for waterfowl. Muskrats and deer eat the entire plant. Stem base and tubers are edible. Native Americans had medicinal uses for giant bur-reed.
Distribution: Both widespread in Northern Hemisphere.
Habitat: Shallow water 1-2.5 m deep in streams, lake margins.
May be confused with: Tapegrass (Vallisneria americana) which is not emergent, and has leaves with rounded tips and a distinctive midrib. Submersed leaves of arrowheads (Sagittaria spp.) or water plantains (Alisma spp.), but the leaves of these 2 groups all arise from the plant base. Small bur-reed (S. nutans) which is smaller with only 1 male flower head and water bur-reed (S. fluctuans) which has a strongly curved beak on the achene. Tall forms of giant bur-reed may be confused with cattail if not blooming. In the spring and early summer, bur-reed plants may not yet be emergent and can be readily confused with tapegrass.
Line Drawings: Sparganium eurycarpum
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