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Slender Bog Arrow-grass (Triglochin palustris)

Life history

Species overview

Slender Bog Arrow-grass (Triglochin palustris), a Wisconsin Special Concern plant, is found on calcareous, moist, open sites, especially fens and lakeshores, as well as in damp areas near sand dunes along the Great Lakes. Blooming occurs throughout July; fruiting occurs throughout August. The optimal identification period for this species is early July through late August.

Synonyms: Triglochin plaustre


  • Distinguishing characteristics: 6 tepals, mature carpels elongate.
  • Flower characteristics: Bisexual; tepals 6, 1 to 1.5 mm; stamens 6; stigmas 3.
  • Fruit characteristics: Fruits in clusters of 3, tapered to the base, with a winged central axis; 3 individual ovaries, 6 to 9 mm each, sharply pointed at base, not rounded.
  • Leaf characteristics: 1 to 2 mm wide, to 3 dm long.


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


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Carex spp., Potentilla palustris, P. anserina, Drosera intermedia, Lycopus americanus, Lobelia kalmii, Carex interior, Eleocharis quinqueflora, Hypericum kalmianum, Gentianopsis procera, Juncus balticus.

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 Slender Bog Arrow-grass (Triglochin palustris). 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 Triglochin palustris in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS3
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 calcareous, moist, open sites, especially fens and lakeshores, as well as in damp areas near sand dunes along the Great Lakes.
  • Soils: Wet soils.

Natural communities

This table lists the natural communities that are associated with Slender Bog Arrow-grass. 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 Slender Bog Arrow-grass. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

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

  • This species is likely sensitive to water quality. Following BMPs around streams and buffering associated drainages will reduce eutrophication and prevent water quality degradation.
  • Avoid rapid and dramatic reductions in canopy cover or basal area in wet areas to reduce risk of swamping.
  • Prescribed burns and/or brushing may be beneficial (dependent on local site conditions).
  • Minimize disturbance to hydrology, including soil disturbance from rutting.


Slender Bog Arrow-grass Photo.

The long, narrow capsules of Triglochin palustris help distinguish it from T. maritima.

Photo by Ryan O'Connor, Wisconsin DNR.

Slender Bog Arrow-grass Photo.

Photo by Ryan O'Connor, Wisconsin DNR.

Slender Bog Arrow-grass Photo.

The flowers of Triglochin palustris.

Photo © Aaron Carlson.

Slender Bog Arrow-grass Photo.

Photo © Aaron Carlson.

Slender Bog Arrow-grass Photo.

Triglochin palustris on left, T. maritima on the right. Notice the much narrower capsules on T. palustris.

Photo by Ryan O'Connor, Wisconsin DNR.

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