Muhlenbergia glomerata (Spike Muhly)

Plant Info
Also known as: Marsh Muhly, Clustered Muhly Grass, Marsh Wild Timothy
Genus:Muhlenbergia
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Habitat:sun; dry to wet; meadows, fens, swamps, marshes, floating mats, shores, jack pine stands
Fruiting season:September - October
Plant height:1 to 4 feet
Wetland Indicator Status:GP: FACW MW: FACW NCNE: OBL
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 Cluster type: spike

[photo of sike-like panicle] A spike-like panicle up to 5 inches long, the panicle branches mostly erect, up to 1 inch long, crowded at the stem tip but usually with distinct gaps between the lowest branches (interrupted). Short-stalked spikelets (flower clusters) are crowded and overlapping on each branch, each spikelet 3 to 8 mm (to ~1/3 inch) long, with a single floret.

[close-up of spikelet] At the base of a spikelet is a pair of bracts (glumes), both similar in size and shape, 1-veined, hairless, awned at the tip, 3 to 8 mm long including the awn and 1.3 to 2 times as long as the floret. Florets are surrounded by a pair of bracts (lemma and palea), the lemma 1.5 to 3.1 mm long, narrowly lance-elliptic, 3-veined, sparsely long-hairy near the base, tapering to a pointed tip, occasionally with an awn up to 1 mm long; the palea is 2-veined, slightly shorter than the lemma, and sparsely long-hairy near the base. The thickened base of the floret (callus) is covered in straight, white hairs up to about 1 mm long.

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

[photo of sheath, ligule and node] Leaves are alternate, 1 to 6 inches long, 2 to 6 mm wide, flat, smooth to rough-textured, hairless except near the base. Sheaths are slightly rough, mostly hairless except near the nodes. The ligule (membrane where the leaf joins the sheath) is up to .6 mm long, more or less straight across the top and may have a sparse fringe of hairs. Nodes are variously covered in short hairs. Stems are mostly erect, unbranched or few-branched at the base, dull, mostly minutely hairy, short-hairy just below the nodes, round in cross-section. Plants are not clump-forming, but create colonies from long, scaly rhizomes.

Fruit: Fruit type: seed without plume

[photo of glumes and floret] Mature florets drop off individually leaving the glumes behind on the stalk. Grains (seeds) are spindle-shaped, 1 to 1.6 mm long, brown.

Notes:

Muhlenbergia is a rather variable genus: clusters spike-like or an open panicle; glumes or lemmas awned, or neither; the callus (base of the floret) covered in long hairs or not; some with hairy stems or sheaths, others hairless; some branched, some not; clump forming or not; annual or perennial. What they have in common are spikelets usually single-flowered (occasionally with 2 or 3 florets), membranous ligules (occasionally also fringed with hairs), narrow leaves, glumes usually 1-veined, lemmas usually 3-veined, paleas 2-veined, and mature florets usually dropping off above the glumes (occasionally at the spikelet branch). There are about 70 species native to North America and more than 150 species worldwide.

Spike Muhly has been found in a variety of habitats, most often in open, moist to wet places including sedge meadows, calcareous fens, swamps, floating mats and lake shores, but sometimes in the drier sites of cliffs and Jack Pine forests. Of the 10 Muhlenbergia species known to be in Minnesota, it is distinguished by the colony-forming growth, stems unbranched or few branched near the base, nodes and the stem below the node visibly short-hairy, awned glumes about equal in size that are up to twice as long as the floret, and the terminal, usually interrupted, spike-like panicle. Florets are long-hairy on the callus and both lemma and palea are sparsely long-hairy near the base.

Spike Muhly is most similar to Marsh Muhly (Muhlenbergia racemosa), which has similar spikelets, but is typically branched from about mid-stem, the branches often leafy, nodes and stems are shinier and hairless, and stems are distinctly elliptic in cross-section, even nearly flat especially near the panicle, easily felt when rolled between your fingers (Spike Muhly stems are round in cross-section).

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More photos

Photos by Peter M. Dziuk taken in Becker, Clay and Pope counties.

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