Muhlenbergia uniflora (Bog Muhly)

Plant Info
Also known as: One-flowered Muhly
Genus:Muhlenbergia
Family:Poaceae (Grass)
Life cycle:perennial
Origin:native
Status:
  • State Special Concern
Habitat:part shade, sun; moist to wet sandy, rocky or peaty soil; bogs, wet meadows, fens, shores, rock pools
Fruiting season:August - September
Plant height:2 to 18 inches
Wetland Indicator Status:GP: OBL MW: OBL 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

[photo of panicle] Open, wispy, branching cluster at the top of the stem, 2½ to 8 inches long, distinctly longer than wide, often with smaller clusters arising from the upper sheaths. Branches are very slender and wiry, mostly ascending. Spikelets (flower clusters) are single at the tips of wiry branchlets, each spikelet 1.3 to 2 mm long usually with a single floret, occasionally 2 florets.

[close-up of branches] At the base of a spikelet is a pair of bracts (glumes), both about the same size and shape, thin, purplish, hairless, 1-veined, blunt to pointed at the tip, about half as long as the spikelet. Florets are surrounded by a pair of bracts (lemma and palea), both similar, longer and thicker than the glumes, 1.2 to 2 mm long, hairless, often turning dark grayish or purplish, the lemma weakly 3-veined and awnless, the palea 2-veined and pointed at the tip.

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

[photo of sheath, ligule, node and stem] Leaves are alternate, 1 to 6 inches long, .5 to 1 mm wide, smooth to rough-textured, mostly flat or sometimes folded, and often crowded with overlapping sheaths especially on the lower stem. Sheaths are keeled on the back and smooth to rough. The ligule (membrane where the leaf joins the sheath) is .5 to 1.5 mm long, usually jagged along the tip edge and lacking a fringe of hairs. Nodes are smooth, often hidden in the sheaths. Stems are hairless, smooth to slightly rough, unbranched, commonly spreading from the base and rising at a lower node (geniculate), rooting at the node, forming loose clumps and sometimes mats.

Fruit: Fruit type: seed_without_plume

[close-up of spikelets] The florets drop off individually when mature leaving the glumes behind on the stalk. Grains (seeds) are brown and less than 1 mm long.

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 cluster branchlet). There are about 70 species native to North America and more than 150 species worldwide.

Bog Muhly is an uncommon grass found in the arrowhead region, where it reaches the western edge of its range, often in shallow soils over bedrock or areas recently flooded where water levels have lowered, such as after snow-melt or following beaver activity. According to the DNR, it was first discovered in 1956 near Gilbert in St. Louis County and the following year in Lake County, but was not seen again for 30 years. It was listed as a Special Concern species in 1996. Since then, biological surveys have located about 25 populations, mostly all within in a few miles of each other in Lake County.

Of the 10 Muhlenbergia species known to be in Minnesota, Bog Muhly is one of two with hairless leaves, stems and sheaths, an open panicle, spikelets up to about 2 mm long and single at branchlet tips, glumes shorter than the lemmas, neither glumes nor lemmas awned, and the callus lacking long hairs. It also has a panicle longer than wide, leaves rarely over 1 mm wide, and stems commonly root at the lower nodes. The other species is Scratchgrass (Muhlenbergia asperifolia), which has a panicle about as wide as long and is found in our western counties, often in saline soils. The panicle of Bog Muhly bears a resemblance to various Panic Grasses (Dichanthelium or Panicum species), which also have single flowered spikelets on wiry branchlets, but have florets that become hardened and shiny with maturity and most have hairy sheaths or leaves and are more strongly clump-forming.

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More photos

Photos by Peter M. Dziuk taken in Lake County.

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