Sparganium eurycarpum Engelm. ssp. eurycarpum

Giant Bur-Reed

Sparganium eurycarpum plant

Family - Sparganiaceae

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

Sparganium_eurycarpum_leafLeaf base.

Sparganium_eurycarpum_leaf2Leaf abaxial.

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

Sparganium_eurycarpum_inflorescenceInflorescence.

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

Sparganium_eurycarpum_flower1Staminate heads.

Sparganium_eurycarpum_flower2Pistillate head.

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.

Sparganium_eurycarpum_fruitFruit.

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 and 5-31-2014, and at Shaw Nature Reserve, Franklin County, MO, 5-30-2014 (SRTurner).



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