Western Wheatgrass (Pascopyrum smithii)

Tribe Triticeae

Rarity Status

Common.

Origin

Native to North America.

Synonyms

Agropyron molle, Agropyron smithii, Agropyron smithii var. molle, Agropyron smithii var. palmeri, Elymus smithii, Elytrigia smithii, Elytrigia smithii var. mollis; common names may include “bluestem,” “bluejoint,” or “western couch grass,” the latter two chosen due to the species’ distinct colour. However, this should not be confused with Little Bluestem (Schizachyrium scoparium) or Big Bluestem (Andropogon gerardi).

Identification

Western Wheatgrass (Pascopyrum smithii) is a native perennial cool-season grass that grows from extensive creeping rhizomes. In other words, it is a creeping sod-forming grass with culms that grow up to 30 to 90 cm tall.

Leaves are stiff and flat to inrolled, 2 to 6 mm wide and 10 to 25 cm long. They are strongly veined, with a roughened texture above (rarely hairy) and smooth below. Notably, they are glaucous and bluish—to purplish-green with roughened margins; blades grow at a 45-degree angle from the culm and are rolled at emergence.

Sheaths are round, glaucous, or scabrous (hairless), with conspicuous veining, open, brownish or purplish at the base. Collars are light green, hairless, continuous, not well-defined, and sometimes bent. Ligules are membraneous, from 0.5 to 1 mm long, truncate, and lacerate or minutely ciliate. Auricles are claw-like and clasping, short (1 to 2 mm long), mostly equal in length, and often purplish, especially at the base.

Inflorescence of P. smithii is in the form of a stiff spike, with spikelets densely collected together, occasionally 2 per node, and closely imbricate (approximately one-half of each spikelet overlaps the base of another). Each spikelet contains 5 to 12 florets, is glaucous, 1.5 to 2.5 cm long. Lemmas are 8 to 14 mm long, acute, glabrous to pubescent on margins. Glumes are generally unequal, with the first glume shorter than the second, 6 to 12 mm long or as long as the lowest lemma, stiff, keeled, asymmetrical, and broadest at the base. Veining is faint, and glabrous to scabrous texture. Awns are minute to sometimes absent.

Blooming Period

Typically blooms from May to June.

Similar Species

It can be confused with Thickspike Wheatgrass (Elymus lanceolatus ssp. lanceolatus), Intermediate Wheatgrass (Thinopyrum intermedium), and Slender Wheatgrass (Elymus trachycaulus). The distinguishing characteristics of P. smithii are the bluish-green tinge of the leaves and the shorter stature compared to most of these other species.

Where to Find This Plant

P. smithii is best known for its abundance in the dry and moist mixed-grass prairies. However, it is also found in the foothills and Aspen Parkland regions, becoming more occasional as one travels northward. This grassland species prefers all soil types but is most abundant in finely textured soils such as loam or clays of the brown chernozemic soils and black chernozems. However, this species prefers low-lying areas with ephemeral poor drainage and some saline and heavy alkaline soils in the dry prairie regions.

Value to Livestock & Wildlife

The forage value of P. smithii is fair to good for all classes of livestock and fair to pronghorn, deer, and other wildlife. Protein content averages 18% in the spring and decreases significantly to 3 to 4% by mid to late fall when plants have reached full maturity. However, the digestible carbohydrates have been shown to increase 40 to 50% during this period, proving their ability to cure well on the stem and make for good fall and winter forage. It is valued as good native hay, and can also be utilized as a stockpiled grazing resource for livestock (as well as historically bison, similarly to Festuca hallii) during the winter months.

This species is regarded as a “decreaser” in very dry regions due to its sensitivity to lack of moisture. However, growing in areas that receive better moisture is considered an “increaser” where it can withstand greater grazing pressure and even compete with other plants for water, space, and nutrients.

Suitability/Use for Reclamation

P. smithii is a popular native species used in land reclamation projects because of its rhizomatous nature and its tolerance of alkaline or saline areas. It will readily move into disturbed areas and work its way along trails. There is no shortage of seed available on the commercial market for such projects

Unfortunately, its seeds are regarded to have poor germination, so the best-recommended way to propagate P. smithii is by daughter tillers from rhizomes.

Toxic, Edible, Medicinal, and Cultural Uses

None have been recorded.

Other Fascinating Information

The growth habits of P. smithii are such that some may consider it opportunistic: it starts regrowth early in the spring, shortly after the frost has left the ground, and after setting seed, it goes dormant during the hot summer months. It will grow again in the fall if adequate soil moisture is used. This species will reproduce from seeds dropped from parent plants and tillers borne from rhizomes that have spread out from such same parents.