Agrostis exarata Trin.
spike bentgrass
Poaceae (Grass family)

Introduction to Vascular Plants


© Jamie Fenneman     (Photo ID #7362)


E-Flora BC Static Map

Distribution of Agrostis exarata
Click here to view the full interactive map and legend

Species Information

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.

SourceThe Illustrated Flora of British Columbia


If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

USDA Species Characteristics

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


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)
394 0 2500
Slope Gradient (%)
9 0 97

Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]

86 10 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
4 0 7
Modal Nutrient Regime
# 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)

Habitat and 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.

SourceThe Illustrated Flora of British Columbia


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