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Horsetail Spike-rush (Eleocharis equisetoides)

Life history

Species overview

Horsetail Spike-rush (Eleocharis equisetoides), a Wisconsin Special Concern plant, is found in the shallow water of emergent marshes, lakeshore edges, and ponds. The single extant Wisconsin occurrence was found in appoximately 60 cm of water in a marl lake with a muck/sand bottom. Fruiting occurs August through October. The optimal identification period for this species is early August through mid October.

Synonyms: Eleocharis elliottii, Scirpus equisetoides


  • Distinguishing characteristics: This species is distinguished by its spikelets, which are 3 to 8 mm wide (not wider than culm), and its culms which are hollow, with complete transverse septa (mostly evident externally).
  • Flower characteristics: Perianth bristles 3-8, stramineous to reddish, slender, vestigial to 2.5 mm, shorter than to equaling achene, smooth or obscurely retrorsely spinulose; anthers stramineous to red-striated, 2.6-3.2 mm; styles 2-3.
  • Fruit characteristics: Achenes yellowish to reddish brown, obovoid, biconvex to obscurely compressed trigonous, 1.8-2.3 x 1.4-1.9 mm, obscurely sculptured or sometimes partially smooth at 10-15X, each face with 20-40 rows of linear, transversely elongated cells, lines separating cells obscure, apex with very short neck 0.6-0.8 mm wide. Tubercles dark brown, lamelliform, high-deltoid, 0.6-1.1 x 0.5-0.7 mm.
  • Leaf characteristics: Distal leaf sheaths persistent, membranous to thinly papery, apex acute to slightly acuminate.


  • Blooming phenology:
  • Fruiting phenology: August through October
  • Optimum time to identify: The optimal identification period for this species is early August through mid October


  • Growth form: Graminoid
  • Vegetative reproduction: Rhizomatous
  • Life cycle: Perennial
  • Comments: Associated Species: Chara, Elodea canadensis, Schoenoplectus tabernaemontani, filamentous algae.

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

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS1
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 the shallow water of emergent marshes, lakeshore edges, and ponds. The single extant Wisconsin occurrence was found in appoximately 60 cm of water in a marl lake with a muck/sand bottom.
  • Soils:

Natural communities

This table lists the natural communities that are associated with Horsetail 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
Lake--Large, Deep, Hard, Drainage 3
Emergent Marsh 3

Ecological landscapes

This table lists the ecological landscape association scores for Horsetail 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
Southeast Glacial Plains 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

  • Maintain and restore open habitat through selective clearing and brushing.
  • This species is likely sensitive to water quality. Following BMPs around streams and buffering associated drainages will reduce eutrophication and prevent water quality degradation.
  • Minimize disturbance to hydrology, including soil disturbance from rutting.


Horsetail Spike-rush Photo.

Photo © Susan Knight.

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