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Clustered Bur-reed (Sparganium glomeratum)

Life history

Species overview

Clustered Bur-reed (Sparganium glomeratum), a Wisconsin Threatened plant, is found in cold ditches and pools within sedge meadows, willow-alder thickets and, occasionally, tamarack stands on the Lake Superior clay plain. Blooming occurs late June through late July; fruiting occurs late July through early September. The optimal identification period for this species is early July through early September.

Synonyms: None


  • Distinguishing characteristics: 1 or 2 staminate heads abutting the upper pistillate head; achene shining.
  • Flower characteristics: Inflorescence simple, occasionally with a basal branch; flowers unisexual; pistillate heads several, sessile 1.5 to 2 cm thick when ripe; staminate head solitary or sometimes 2, abutting pistillate heads below.
  • Fruit characteristics: Achene brown, shining, fusiform body, 3 to 4 mm, slighly constricted below the middle, tapering to a straight or slightly curved beak 1.5 to 2 mm.
  • Leaf characteristics: Flat or weakly keeled, 3 to 8 mm wide; bracteal leaves dilated at the base.


  • Blooming phenology: late June through late July
  • Fruiting phenology: late July through early September
  • Optimum time to identify: The optimal identification period for this species is early July through early September


  • Growth form: Aquatic forb-emergent/floating
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Salix petiolaris, Alnus rugosa, Calamagrostis canadensis, Cornus stolonifera, Petasites sagittatus, Eleocharis nitida, Ranunculus gmelinii.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Clustered Bur-reed (Sparganium glomeratum). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Sparganium glomeratum in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusTHR
Federal Status in Wisconsinnone
State RankS2
Global RankG4?
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found in cold ditches and pools within sedge meadows, willow-alder thickets and, occasionally, tamarack stands on the Lake Superior clay plain.
  • Soils: Wet soils.

Natural communities

This table lists the natural communities that are associated with Clustered Bur-reed. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Ecological landscapes

This table lists the ecological landscape association scores for Clustered Bur-reed. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Ecological landscape score
Northwest Lowlands 2
Northwest Sands 1
Superior Coastal Plain 3

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.
  • Avoid broadcast spraying of herbicides; use care with spot spraying.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • Minimize disturbance to hydrology, including soil disturbance from rutting.
  • Survey for and control invasive plants prior to conducting timber operations, as these can be spread by vehicles and often respond vigorously to increased light; see forestry BMPs for invasive species.


Clustered Bur-reed Photo.

The clustered bur-reed has been documented at several locations within this ecological landscape.

Photo © June Dobberpuhl.

Clustered Bur-reed Photo.

Photo © Daniel Spuhler.

Clustered Bur-reed Photo.

Photo © June Dobberpuhl.

Clustered Bur-reed Photo.

Photo © Daniel Spuhler.

Clustered Bur-reed Photo.

Photo © Daniel Spuhler.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition