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Spike Trisetum (Trisetum spicatum)

Life history

Species overview

Spike Trisetum (Trisetum spicatum), a Wisconsin Threatened plant, is found in moist, shaded mossy sandstone ledges on Lake Superior. Blooming occurs throughout June; fruiting occurs throughout July. The optimal identification period for this species is late June through early August.

Synonyms: Aira spicata, Trisetum triflorum, Trisetum triflorum ssp. molle, Trisetum villosissimum, Trisetum spicatum ssp. alaskanum, Trisetum spicatum ssp congdonii, Trisetum spicatum ssp. majus


  • Distinguishing characteristics: Exceedingly variable; two more outstanding varieties, both intergrading with the species are: T. spicatum var. molle with densely pubescent foliage, and T. spicatum var. congdoni, a nearly glabrous alpine form with slightly larger spikelets.
  • Flower characteristics: Panicle dense, usually spike-like, often interrupted at base, pale or often dark purple, 5 to 15 cm long; spikelets 4 to 6 mm long.
  • Fruit characteristics: Glumes somewhat unequal in length, glabrous or scabrous except the keels, or sometimes pilose, the first narrow, acuminate, 1-nerved, the second broader, acute, 3-nerved; lemmas scaberulous, 5 mm long, the first longer than the glumes, the teeth setaceous; awn attached about one-third below the tip, 5 to 6 mm long, geniculate, exserted.
  • Leaf characteristics: Sheaths and usually the blades puberulent.


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


  • Growth form: Graminoid
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Pinguicula vulgaris, Alnus viridis, Abies balsamea, Primula mistassinica, Thuja occidentalis, Agrostis hyemalis, Lycopodium.

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 Spike Trisetum (Trisetum spicatum). 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 Trisetum spicatum in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusTHR
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 moist, shaded mossy sandstone ledges on Lake Superior.
  • Soils: Moist soils.

Natural communities

This table lists the natural communities that are associated with Spike Trisetum. 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 Spike Trisetum. 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 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.
  • Avoid direct disturbance to sensitive microsites such as seeps, cliffs, and moss-covered boulders.

Management guidance

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

  • Follow BMPs, especially around streams and use care near ravines, steep slopes, cliffs, rock outcrops, etc.
  • Minimize disturbance to hydrology, including soil disturbance from rutting.


Spike Trisetum Photo.

Photo by Ryan O'Connor, Wisconsin DNR.

Spike Trisetum Photo.

Photo © Emmet Judziewicz.

Spike Trisetum Photo.

Photo © Emmet Judziewicz.

Spike Trisetum Photo.

Photo © Emmet Judziewicz.

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