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Wisconsin Plant of the Week

Sparganium eurycarpum Engelm. ex A. Gray

Sparganiaceae

Common Name:

common bur-reed

07/12/1999

Common bur-reed is a native perennial found in shallow water at the edges of rivers and marshes. It grows where water depth seldom exceeds 0.5 m and spreads by both seed and rhizomes.  Itís the most common and the most robust of the seven species of Sparganium in N. America.

All Sparganium species have similar white or greenish flowers in dense round heads. The upper heads are staminate (male), the lower heads are pistillate (female) developing into bur-like fruit composed of many nutlets.  Flowers bloom in June and July.

Mature nutlets are needed to determine the species of Sparganium except for S. eurycarpum.  Its flowers have 2 stigmas, while flowers of the other species have a single stigma.  The nutlets are also distinctive in that they are broadest (5 to 8 mm) at the square tip, like an inverted pyramid.

Emergent leaves are erect, to more than 1 m long, and strongly keeled, so that they appear triangular in cross-section -- unlike the leaves of Iris, which are flat, and Cattail, which are slightly D-shaped in section. Unlike most sedges, whose leaves are triangular and 3-ranked, the leaves of Sparganium are 2-ranked.

  • Origin of the name: Sparganium, L., for bur-reed; eurycarpum, eury-, Gk., broad or wide; carpum, Gk., karpos, fruit
  • Range:  Quebec to BC, s. to VA. OK, CA
  • WI Range:  Statewide
  • Common associates:  Iris, bulrushes, cattail, carices
  • Wetland Indicator Status: OBL
  • Coefficient of Conservatism: C = 6 (S&W), C = 5 (MI)
     
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