Poa palustris (Fowl Bluegrass)

Plant Info
Also known as: Swamp Meadow-grass
Genus:Poa
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Habitat:part shade, sun; dry to wet sandy or rocky soil; wet meadows, prairies, shores, swamps, bogs, forest edges, jack pine stands, bluffs
Fruiting season:July - August
Plant height:1 to 4 feet
Wetland Indicator Status:GP: FACW MW: FACW NCNE: FACW
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: panicle

[scan of panicle] Panicle 4 to 10+ inches long with 2 to 9 branches at each node, the lowest nodes usually with 5, and spikelets (flower clusters) mostly on the tip half of a branch. Branches are typically initally nodding to one side but soon become spreading to slightly drooping, the open panicle pyramidal to egg-shaped in outline. Spikelets are green to purplish when fresh, flattened, lance-elliptic in outline, 3 to 5 mm (to ~¼ inch) long with 2 to 4 florets; the uppermost floret may be sterile.

[close-up of branch and spikelet] At the base of a spikelet is a pair of bracts (glumes) that are both pointed at the tip, awnless, hairless, keeled, smooth to slightly rough along the keel, 3-veined, the upper glume 2.5 to 3.5 mm long, the lower glume about the same or slightly smaller. Surrounding a floret is a pair of bracts (lemma and palea), the lemma 2 to 3 mm long, rounded to pointed at the tip, keeled, 3-veined, with long white hairs along the lower half of the veins, the surface between them hairless; the palea is somewhat shorter than the lemma, 2-veined, hairless. The thickened base of the floret (callus) has a sparse to dense tuft of long, crinkly hairs; the stalk between florets (rachilla) is hairless.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of sheath, node, ligule and leaf tip] Leaves are mostly basal with 3 or 4 alternate leaves widely spaced along the stem. Leaves are mostly flat, (1)2 to 6(8) mm (mostly less than ¼ inch) wide, hairless, slightly rough, boat-shaped at the tip. Stem leaves are mostly spreading to ascending, rarely more than 4 inches long; basal leaves are to ~8 inches long. The sheath is hairless and the edges are fused for up to 1/5 their length (closed sheath). The ligule (membrane where the leaf blade joins the sheath) is 2 to 6 mm long, variable across the top edge and lacks a fringe of hairs. Nodes are smooth. Stems are mostly unbranched, erect to ascending, multiple from the base forming loose to dense clumps. Late in the season new shoots emerge from the basal sheaths, spreading horizontally before rising up (decumbent) and may root at the lower nodes.

Fruit: Fruit type: seed without plume

[photo of mature florets] Individual florets drop away when mature, leaving the glumes behind persisting on the stalk. The grain (seed) is golden to brown.

Notes:

Fowl Bluegrass is a common cool-season grass most often found in moist to wet places including wet meadows, prairie swales, wetland edges, shores, river banks and floodplains, sometimes drier sites such as Jack pine stands, dry prairie and bluffs, but almost always in sandy or rocky soil. Its native range covers parts of North America (including Minnesota), Europe and Asia.

Poa species are recognized by their (usually) closed sheaths, leaves with boat-shaped tips, and often long, crinkly hairs around the base of the floret (callus). Fowl Bluegrass is distinguished by its clump-forming growth; flat leaves (1)2 to 6(8) mm wide; ligule often ~5 mm long (2 to 6+ mm); sheaths closed for only up to 1/5 their length; panicle initially nodding to one side, the branches becoming spreading to slightly drooping, usually 5 branches (up to 9) on the lowest nodes, spikelets along the tip half of a branch; 2 to 4 florets per spikelet; lemmas 2 to 3 mm long, 3-veined, long hairs along the lower half of the veins, callus sparsely to moderately covered in long, crinkly hairs. The clumps can be loose or dense, with few or many stems from the base.

It is most likely to be confused with Kentucky Bluegrass (Poa pratensis), which blooms and matures weeks earlier, but also has a shorter ligule (usually less than 2 mm), lemmas with 5 distinct veins (hairy on 3), and is rhizomatous rather than clump-forming. Its panicle also tends to be shorter and narrower than Fowl Bluegrass, the branches often contracting and nodding to one side as it dries down. Fowl Bluegrass struck me as more wispy in appearance, where Kentucky Bluegrass seemed more coarse.

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More photos

Photos be K. Chayka taken in Anoka and Washington counties. Photos by Peter M. Dziuk taken in Ramsey County. Late season shoots by Matt Lavin, via Wikimedia Commons, used under CC BY-SA 2.0

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