Poa alsodes (Grove Bluegrass)

Plant Info
Also known as: Wood Bluegrass, Grove Meadow Grass
Genus:Poa
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Habitat:part shade, shade; average to wet soil; rich woods, thickets, floodplains, seeps, river banks, swamps
Fruiting season:June - July
Plant height:1 to 4 feet
Wetland Indicator Status:GP: none MW: FACW NCNE: FAC
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] Open panicle 4 to 14 inches long, usually erect and pyramidal in outline, sometimes slightly nodding, the branches ascending to spreading, with 2 to 7 branches (usually 4 or 5) at a node and a few spikelets (flower clusters) along the tip half of a branch. Spikelets are light green at flowering time, flattened, lance-elliptic in outline, 3.5 to 6.7 mm (to ~¼ inch) long with 2 to 4 florets; the uppermost floret may be sterile.

[close-up of spikelet] At the base of a spikelet is a pair of bracts (glumes) that are both pointed at the tip, awnless, hairless, keeled, rough along the keel, the upper glume 3 to 3.5 mm long and 3-veined, the lower glume somewhat smaller and 1-veined. Surrounding a floret is a pair of bracts (lemma and palea), the lemma 2.7 to 4.2 mm long, pointed at the tip, keeled, 5-veined, with long white hairs only along the lower half to 2/3 of the keel, the lateral veins and surface between them hairless; the palea is nearly as long as the lemma, 2-veined, rough or hairy along the veins. The thickened base of the floret (callus) has a tuft of long, crinkly hairs; the stalk between florets (rachilla) is hairless.

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

[photo of sheath, ligule and leaf tip] Leaves are mostly basal with 2 or 3 alternate leaves widely spaced along the stem. Leaves are mostly flat, thin, .8 to 5 mm (less than ¼ inch) wide, hairless, boat-shaped at the tip. Stem leaves are mostly ascending to spreading, rarely more than 4 inches long; basal leaves are floppy and to 8+ inches long. The sheath is hairless and the edges are fused for half to 7/8 their length (closed sheath). The ligule (membrane where the leaf blade joins the sheath) is usually less than 2 mm long, often ragged along the top edge and lacks a fringe of hairs. Nodes are smooth. Stems are unbranched, erect to ascending, multiple from the base forming loose to dense clumps, and lack rhizomes or stolons.

Fruit: Fruit type: seed without plume

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

Notes:

Grove Bluegrass is a native, cool-season grass typically found in moist to wet woods, swamps, river banks and floodplains. It reaches the western edge of its range in Minnesota.

Poa species are recognized by their (usually) closed sheaths, leaves with boat-shaped tips, and often long, cobwebby hairs around the base of the floret (callus). Grove Bluegrass is distinguished by its clump-forming growth; thin, flat leaves 1.5 to 5 mm wide, the upper stem leaves rarely more than 4 inches long and the basal leaves longer and more lax; ligule less than 2 mm long; sheaths closed for half to 7/8 their length; open panicle, usually 4 or 5 branches per node, a few spikelets along the tip half of a branch; 2 to 4 florets per spikelet; florets 2.7 to 4.2 mm long, hairy only along the lemma keel and callus.

The hairs only on the lemma keel and callus is fairly unique; the only other species in Minnesota that has this combination is the non-native Poa trivialis (Rough Bluegrass), which usually has a more densely flowered panicle, has sheaths closed for not more than half their length, and a much longer ligule, 2.5 to 10 mm long. The few-flowered panicles of Poa alsodes may resemble Poa saltuensis (Old Pasture Bluegrass), which has only 1 to 3 branches per node and usually hairless lemmas, and Poa paludigena (Bog Bluegrass), which only has 1 or 2 branches per node and lemmas are hairy on both the lateral veins and keel.

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More photos

Photos by K. Chayka and Peter M. Dziuk taken at Banning State Park, Pine County, and in the garden.

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