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Grassleaf Rush (Juncus marginatus)

Life history

Species overview

Grassleaf Rush (Juncus marginatus), a Wisconsin Special Concern plant, is found in acid peaty ditches and depressions in pine and oak barrens. Blooming occurs early July through early August; fruiting occurs throughout August. The optimal identification period for this species is early July through early August.

Synonyms: Juncus marginatus var. biflorus, J. marginatus var. odoratus, J. marginatus var. setosus, J. biflorus, J. setosus


  • Distinguishing characteristics: Plants mostly 20 to 50 cm tall, with 15 to 20 heads; main leaf blades 1 to 3 mm wide, flat to involute, lacking hard cross partitions; stems densely cespitose, bulbous-thickened at the base.
  • Flower characteristics: Flowers subtended by paired bracteoles; petals 2.3 to 3.3 mm, oblong with broadly thin, dry margins; stamens 3, nearly as long as the tepals; anthers reddish-brown, much shorter than the filaments, usually soon shriveling.
  • Fruit characteristics: Incompletely 3-locular, the partitions not meeting in the center, somewhat turgid-inflated, 1.8 to 2.9 mm long and nearly as thick.
  • Leaf characteristics: Principle blades flat to involute, 1 to 3 mm wide, with 2-3 prominent veins, lacking hard cross-partitions; leaf sheaths with small, rounded, thin-dry, ear-shaped appendages.


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


  • Growth form: Graminoid
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Pinus banksiana, Viola lanceolata, Rhynchospora capitellata, Muhlenbergia uniflora, Calopogon tuberosus, Juncus canadensis, J. brevicaudatus.

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 Grassleaf Rush (Juncus marginatus). 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 marginatus in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS2
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 acid peaty ditches and depressions in pine and oak barrens.
  • Soils: Wet, acidic, peaty soils.

Natural communities

This table lists the natural communities that are associated with Grassleaf 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).

Ecological landscapes

This table lists the ecological landscape association scores for Grassleaf Rush. 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 site preparation that heavily disturbs herbaceous ground layer and soil; these include bulldozing and furrowing, as well as grubbing and stump removal.
  • Avoid broadcast spraying of herbicides; use care with spot spraying.
  • Avoid locating landings, staging areas, or access routes in open sandy areas dominated by native grasses.

Management guidance

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

  • 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.
  • Prescribed burns and/or brushing may be beneficial (dependent on local site conditions).
  • Maintain and restore open habitat through selective clearing and brushing.


Grassleaf Rush Photo.

Photo © Karen A. Rawlins,

Grassleaf Rush Photo.

Photo © Karen A. Rawlins,

Grassleaf Rush Photo.

Photo by Kevin Doyle, 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
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