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Kevin Doyle

Bog Rush (Juncus stygius)

Life history

Species overview

Bog Rush (Juncus stygius), a Wisconsin Endangered plant, is found in cold fens. Blooming occurs late June through early July; fruiting occurs throughout July. The optimal identification period for this species is early July.

Synonyms: Juncus stygius ssp. americanus, Juncus stygius var. americanus


  • Distinguishing characteristics: Seeds 2 to 3 mm with pale tails or appendages at both ends; 6 stamens; leaves very slender.
  • Flower characteristics: Inflorescence of 1 to 3 compact heads, each 1- to 4-flowered, 1 cm; petals wide and obtuse; stamens 6; anthers much shorter than the filaments.
  • Fruit characteristics: Ellipsoid, 6 to 8.5 mm, conspicuously tipped with a short, sharp, abrupt point; seeds 2 to 3 mm, with a thick pale appendage (or tail) at each end about as long as the body.
  • Leaf characteristics: Basal leaves 1 to 3, or one cauline leaf above the middle; blades very narrow, sheaths firm, usually with slightly prolonged ear-shaped appendages.


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


  • Growth form: Graminoid
  • Vegetative reproduction: Rhizomatous
  • Life cycle: Perennial
  • Comments: Associated Species: Carex livida, Scirpus hudsonianus, Xyris montana, Arethusa bulbosa, Rhynchospora fusca, Utricularia cornuta, Triglochin maritimum, Calopogon tuberosus.

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 Bog Rush (Juncus stygius). 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 Juncus stygius in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusEND
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 in cold fens.
  • Soils: Wet soils.

Natural communities

This table lists the natural communities that are associated with Bog 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
Boreal Rich Fen 2
Poor Fen 3

Ecological landscapes

This table lists the ecological landscape association scores for Bog 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
North Central Forest 2
Northern Highland 2

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.
  • 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.
  • Minimize disturbance to hydrology, including soil disturbance from rutting.
  • Avoid rapid and dramatic reductions in canopy cover or basal area in wet areas to reduce risk of swamping.


Bog Rush Photo.

Photo ©  Wisconsin DNR.

Bog Rush Photo.

Photo by Kevin Doyle, Wisconsin DNR.

Bog Rush Photo.

Photo by Kevin Doyle, Wisconsin DNR.

Bog Rush Photo.

Photo by Ryan O'Connor, Wisconsin DNR.

Bog Rush Photo.

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