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Grasses of the Eloise Butler Wildflower Garden

The oldest public wildflower garden in the United States

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Common Name
Canada Bluegrass

 

Scientific Name
Poa compressa L.

 

Plant Family
Poaceae (Grasses)

Garden Location
Upland & Woodland

 

Prime Season
Spring to Early Summer, then cool Late Summer into Fall

 

Grass structure and definitions - PDF from Oregon State University

Ligule Types, Shapes & Margins (pdf)

 

Canada Bluegrass was introduced from Eurasia as a plant for soil stabilization. The stems (culms) are 6 to 24 inches tall, strongly compressed to a flattened oval, and usually with a sharp bend near the base. Nodes are also strongly compressed. Stems are usually solitary but may be loosely tufted occasionally.

Leaves: The stem blades are flat, narrow, up to 5/32 inch wide (to 4 mm), and up to 4 inches long, tapered, with a narrow keel (boat-shape) at the tips. The margins are rough, the upper surface may be smooth or have roughness over the two main veins down the middle of the leaf. Middle stem leaves are the longest. Color is a blue/green.

Sheaths and ligules: The leaf sheath is split at the top but closed for 1/10 to 1/5 the length at the base, distinctly compressed like the stem, basal sheaths without hair at their bases. Ligules are 1 to 3 mm long, rough, with obtuse tips that have marginal cilia.

Inflorescence: The flowering panicle has an erect ovoid pyramidal shape, 1/6 to 1/3 as wide as long, 2 to 10 cm long (to 4 inches), with 15 to 80 spikelets and 1 to 3 branches per node. The branches are erect to ascending, rarely spreading, very rough on the angles, with 1 to 15 spikelets per branch, usually crowded toward the ends of the branches.

The spikelets are 3.5 to 7 mm long, laterally compressed. They have 3 to 7 florets each. The glumes are mostly equal in size, usually distinctly shorter than the adjacent lemmas, distinctly keeled with the keel having sparse to dense fine rough hairs. The lower glume 3 veined, lanceolate in shape. The lemmas are 2.3 to 3.5 mm long, lanceolate in shape, distinctly keeled, the keels and marginal veins with short fine hairs. The tips of the lemmas usually have some bronze color. Below the lemma keel at the callus there usually appears a web of crimped hairs. There are 3 anthers.

Seeds are very small, to 3+ mm long, ellipsoidal in shape. Florets are wind pollinated.

 

Habitat: Canada Bluegrass has an extensive rhizomatous root system allowing it to spread aggressively. It can become very invasive. Full sun and adequate moisture are needed for good growth. It is adapted to wet sites and moderately acidic soils, hence its use for erosion control. It is palatable to browsing livestock but does not produce abundant foliage. It is adapted to colder temperatures and the leaves may stay green into early winter. It does not form dense sod like Kentucky Bluegrass and regrowth from cutting is slow.

Names: The genus Poa is the Greek word for grass. The species name, compressa, means 'flattened' referring to the shape of the stem. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.

Comparisons: Canada Bluegrass, is one of two species in the Poa section Tichopoa and the only one of those two found in North America. The main characteristic is strongly compressed stems and a rhizomatous root system. The other Bluegrass that is somewhat similar in appearance and found in the same general area is Kentucky Bluegrass, P. pratensis. It has a darker green foliage, has longer and more parallel leaf blades, a shorter ligule and a much more rounded stem. Also the panicle has branches that are less rough and more of them. It also matures earlier. Several cultivars of Canada Bluegrass have been released by the nursery trade for landscape use and seed production.

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.

panicle Illustration

Above: Panicle of Canada Bluegrass in development stage. Photo ©Robert Mohlenbrock, USDA-NRCS Plants Database. Illustration by Sandy Long, ©Utah State University.

Below: Detail of the spikelet of Canada Bluegrass, ©Anna Gardner, Iowa State University. Illustration from Flora Batavia.

Spikelet detail botanical illustration

Below: 1st photo - shape of the mature panicle, photo ©Emmet J. Judziewicz, Wisconsin Flora. 2nd photo - seed detail, photo ©Steve Hurst, USDA-NRCS Plants Database

mature panicle seeds

Notes:

Canada Bluegrass is a perennial currently believed to have been introduced from Europe into Canada around 1700 and now found throughout the United States and Canada except for Florida. Its spread is sometimes thought to have occurred by intermixing of seed with those of Kentucky Bluegrass. In Minnesota it is present in most of the counties in the State. It is one of 18 species of Poa found in Minnesota, 10 of which are considered native grasses.

References and site links

References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

graphicIdentification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.



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