Canby's Bluegrass 
Aira brevifolia Pursh or
Poa canbyi (Scribn.) T.J. Howell

Collected most probably along the trail toward Weippe Prairie northeast of Kamiah in Idaho Co., Idaho, on 10 Jun 1806. (Source)

Canby's bluegrass is a green or glaucous, densely tufted, culms are 4 to 7 dm tall, often tinged with purple below. Plants usually naked in upper half, the leaves forming large basal rosettes. It has short leaves with boat-shaped tips and a purplish panicle--a branched cluster of flowers. It is a vigorous, long-lived perennial, with excellent early spring growth. Canby bluegrass grows to 24 inches in height, Canby demonstrates more vigor, later maturity, and greater forage production than some bluegrasses. Canby matures in June. The seed matures in mid-June, plants then become dormant until fall rains begin. Plant growth begins in the fall and growth rates are rapid in early spring in order to set seed before soil moisture is gone.Canby occurs in the 10 to 25 inch precipitation zone, below timberline.  It grows well on sites receiving short-season moisture; when available moisture is gone, the plant goes dormant, enabling it to survive on dry, shallow, rocky sites, or sagebrush slopes. A native Intermountain region.