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Mamillate Spike-rush (Eleocharis mamillata)

Life history

Species overview

Mamillate Spike-rush (Eleocharis mamillata), a Wisconsin Special Concern plant, is found on the edge between wet meadow and shrub-carr and on sphagnum-sedge bog mat in Wisconsin. Rangewide, it has been found on fresh lakeshores, shallow ponds, streams, floating mats, bogs, fens, and ditches. Blooming occurs mid-May through late August; fruiting occurs mid-June through late September. The optimal identification period for this species is mid-June through late September.

Synonyms: None


  • Distinguishing characteristics: Often confused with E. palustris and E. macrostachya. They are differentiated by perianth (flower) bristles and achenes.
  • Flower characteristics: Perianth (flower) bristles (4-) 5 to 6 (-8), brown, slender to stout, mostly exceeding the tubercles, to twice as long as the achene; stamens 3.
  • Fruit characteristics: Achenes not persistent, yellow maturing to straw-colored, biconvex with obscure angles, apex rounded with no neck; tubercles brown to partly white.
  • Leaf characteristics: Distal leaf sheaths persistent, often splitting away from the stem, usually reddish close to the stem and turning to straw-colored further from the stem.


  • Blooming phenology: mid-May through late August
  • Fruiting phenology: mid-June through late September
  • Optimum time to identify: The optimal identification period for this species is mid-June through late September


  • Growth form: Graminoid
  • Vegetative reproduction: Rhizomatous
  • Life cycle: Perennial
  • Comments: Associated Species: Salix gracilis, Alnus rugosa, Carex lacustris, Cyperus cyperinus.

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 Mamillate Spike-rush (Eleocharis mamillata). 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 Eleocharis mamillata in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS1
Global RankG5
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 on the edge between wet meadow and shrub-carr and on sphagnum-sedge bog mat in Wisconsin. Rangewide, it has been found on fresh lakeshores, shallow ponds, streams, floating mats, bogs, fens, and ditches.
  • Soils: Moist to wet soils.

Natural communities

This table lists the natural communities that are associated with Mamillate Spike-rush. 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).

Natural communities score
Northern Sedge Meadow 3

Ecological landscapes

This table lists the ecological landscape association scores for Mamillate Spike-rush. 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
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 broadcast spraying of herbicides; use care with spot spraying.
  • 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.

Management guidance

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

  • Maintain and restore open habitat through selective clearing and brushing.
  • Prescribed burns and/or brushing may be beneficial (dependent on local site conditions).
  • Minimize disturbance to hydrology, including soil disturbance from rutting.


Mamillate Spike-rush Photo.

Specimen scanned by the Wisconsin Herbarium, Madison, WI.

Scanned specimen courtesy of Wisconsin Herbarium

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