Sparganium eurycarpum Engelm.

Giant Bur-Reed

© SRTurner

Family - Sparganiaceae

Leaves - Alternate, 2-ranked, with sheathing bases, parallel veined, to 1 m long, 12 mm wide, keeled, glabrous.

	Leaf base.
© SRTurner

	Leaf abaxial.
© SRTurner

Inflorescences - Plants monecious. Flowers in dense globose clusters, which are sessile, irregular, and alternate along upper stem. Staminate heads located above pistillate heads.

	Inflorescence.
© SRTurner

	Inflorescence. Pistillate clusters (maturing to fruits) are at bottom, with staminate clusters above.
© SRTurner

Flowers - Minute. Ovary superior. Stigmas 2 per flower, 2.0-3.5 mm long.

	Staminate heads.
© SRTurner

	Pistillate head, with two stigmas per flower.
© SRTurner

Fruit - Fruiting heads 2-5 cm in diameter. Fruits shiny, the body 6-10 mm long, broadly wedge-shaped, broadest near the tip, the beak 2-4 mm long.

	Maturing fruit cluster.
© SRTurner

	Fruits. Fruits are wedge-shaped and broadest near the tip, with the style remnant forming a short beak.
© SRTurner

Flowering - May - August.

Habitat - Emergent aquatic in ponds, sloughs, marshes, fens.

Origin - Native to the U.S.

Other info. - This genus is easily recognized by its aquatic habitat and monecious habit, with the staminate and pistillate inflorescences borne on the same stalk but appearing very different. S. eurycarpum can be distinguished from the other two Missori species of Sparganium by virtue of having two stigmas per flower. These are persistent for some time during fruit maturation. The fruiting heads are distinctive in appearance, reminiscent of medieval maces. The fruits are a food source for waterfowl, and are dispersed by floating on water.

Photographs taken at Marais Temps Clair Conservation Area, St. Charles County, MO, 6-4-2012, 5-31-2014, 7-28-2020, and 5-31-2021, and at Shaw Nature Reserve, Franklin County, MO, 5-30-2014 (SRTurner).