E-Flora BC: Electronic Atlas of the Flora of British Columbia

Agrostis exarata Trin.
spike bentgrass
Poaceae (Grass family)

Introduction to Vascular Plants

© Jamie Fenneman  Email the photographer   (Photo ID #7362)

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Distribution of Agrostis exarata
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Species Information

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Perennial, tufted grass from fibrous roots, some of the shoots non-flowering; stems 20-100 cm tall.
Sheaths smooth to rough-hairy; blades 4-15 cm long, 2-8 mm wide, flat; ligules 2.5-4 mm long, rough-hairy outside.
Inflorescence spikelike, dense, narrowly egg-shaped or lanceolate, occasionally interrupted near the base, 4.5-18 cm long, the branches ascending or appressed, barely visible, densely covered with spikelets to the base; spikelets numerous, crowded; glumes 1.5-3.5 mm long, pointed or narrowly tapering to fine points, the surfaces smooth or rough-hairy, especially on the keels; lemmas 1.2-2.2 mm long, awnless or some awned from above the middle on the back, the awns to 3.5 mm long, straight or bent; calluses sparsely to abundantly hairy, the hairs to 0.3 mm long; rachillas not prolonged; paleas variable, absent or if present, only as a minute membrane to 0.5 mm long; anthers 0.3-0.6 mm long.
A. exarata exhibits marked variation. Awned and awnless spikelets may occur on separate plants or in the same inflorescence. Plants also vary greatly in total height and size and colour of the inflorescence. For these reasons, several varieties have been proposed.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Late Spring
Fruit/Seed characteristics:
Colour: Brown
Present over the Summer
Source:  The USDA

Habitat / Range

Mesic to wet fields, tidal marshes, beaches, meadows, river bars, roadsides and disturbed sites in the lowland, steppe and montane zones; common throughout BC; amphiberingian, N to AK, YT and NT, E to S SK, and S to TX, NM, AZ and CA; E Asia, S America.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Agrostis exarata

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 0 394 2500
Slope Gradient (%) 0 9 97
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
10 86 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 4 7
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: AT(1), BWBS(2), CDF(20), CMA(1), CWH(109), ESSF(14), ICH(4), IDF(1), IMA(1), MH(5), MS(5), PP(2), SBPS(1), SBS(1)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Agrostis aenea Trin.
Agrostis alaskana Hultén
Agrostis ampla Hitchc.
Agrostis asperifolia Trin.
Agrostis exarata subsp. exarata
Agrostis exarata subsp. exarata
Agrostis exarata subsp. minor (Hook.) C.L. Hitchc.
Agrostis exarata var. minor Hook.
Agrostis exarata var. monolepis (Torr.) Hitchc.
Agrostis exarata var. pacifica Vasey
Agrostis exarata var. purpurascens Hultén
Agrostis longiligula Hitchc.
Agrostis longiligula var. australis J.T. Howell
Agrostis melaleuca (Trin.) Hitchc.
Agrostis microphylla var. major Vasey

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References