Slideshow image
Muhlenbergia sobolifera (Muhl. ex Willd.) Trin.
Family: Poaceae
Rock Muhly
[Achnatherum soboliferum (Muhl. ex Willd.) P. Beauv.,  more]
Muhlenbergia sobolifera image

Plants perennial; rhizomatous, usually not cespitose. Culms 25-95 cm tall, 0.8-1.5 mm thick, erect or ascending; internodes smooth, shiny, and glabrous for most of their length, scabridulous immediately below the nodes. Sheaths glabrous, margins hyaline; ligules 0.3-1 mm, membranous, truncate, ciliolate; blades 4-16 cm long, 2-7 mm wide, flat, glabrous, usually smooth, occasionally scabridulous. Panicles 4-18 cm long, 0.2-0.8 cm wide, narrow, usually exserted; axillary panicles usually exserted, sometimes partially included in the subtending sheath; primary branches 0.6-4 cm, ascending to appressed; pedicels 0.3-1.6 mm, strigose. Spikelets 1.6-3 mm, erect, overlapping the next spikelet on the branch by 1/2 its length. Glumes equal to subequal, 1-2.5 mm, much shorter than the florets, scabridulous (particularly over the veins), 1-veined, narrowing from above the broad, overlapping bases to the acute apices, unawned or awned, awns to 1 mm; lemmas 1.6-2.8 mm, lanceolate, hairy on the calluses, lower 1/2 of the midveins, and margins, hairs 0.3-0.5 mm, apices acuminate, unawned or awned, awns to 1 mm; paleas 1.6-2.9 mm, lanceolate, basal 1/2 with hairs shorter than 1. 5 mm, apices scabridulous, acuminate; anthers 0.4-1 mm, yellow. Caryopses 1-1.5 mm, fusiform, brown. 2n = 40.

Muhlenbergia sobolifera grows in dry upland forests, oak woodlands, and on rock outcrops of sandstone, chert, or limestone formations, at elevations of 0-1200 m. It is restricted to the Flora region.

Perennial rhizome-bearing herb 25 cm - 1.13 m tall Leaves: having hairless, open, transparent-margined sheaths and 0.3 - 1 mm long, flat-topped, membranous ligules that are lined with hairs along the margins. The blades are 4 - 16 cm long, 2 - 7 mm wide, flat, hairless, and usually smooth but sometimes minutely rough. Inflorescence: terminal, spike-like and branched (panicle), 4 - 18 cm long, 0.2 - 0.8 cm wide, with ascending to appressed primary branches 0.6 - 4 cm long, and the base of axillary inflorescences occasionally surrounded by the sheath. Fruit: a brown, spindle-shaped caryopsis, 1 - 1.5 mm long. Culm: 25 cm - 0.95 m long, erect to ascending, 0.8 - 1.5 mm wide, the internodes minutely rough just below nodes but shiny and hairless elsewhere. Spikelets: borne on appressed-hairy stalks 0.3 - 1.6 mm long, erect, 1.6 - 3 mm long, overlapping half the length of the spikelet above it. Glumes: equal or nearly so, 1 - 2.5 mm long, egg-shaped with a broad base and pointed tip, sometimes terminating in an awn to 1 mm long, single-veined, minutely rough. Florets: with yellow anthers 0.4 - 1 mm long. Lemma: 1.6 - 2.8 mm long, lance-shaped with a pointed tip, sometimes terminating in an awn to 1 mm long, three-veined, with hairs 0.3 - 0.5 mm long along the bottom half of the midvein and along the margins. Palea: 1.6 - 2.9 mm long, lance-shaped with a minutely rough and pointed tip, two-veined, with hairs less than 1.5 mm long on the lower half.

Similar species: The following species also have shiny, mostly hairless culms. The glumes of Muhlenbergia schreberi are missing or minute, and those of Muhlenbergia x curtisetosa are unequal and sometimes awned. Muhlenbergia racemosa has awned, narrow, 3 - 8 mm long glumes that are much longer than the lemmas and end in a minutely rough awn. The narrow, 1.4 - 2 mm long, sometimes awned glumes of Muhlenbergia bushii are shorter than the lemmas, and the ligules are 0.2 - 0.6 mm long. Muhlenbergia frondosa has narrow, 2 - 4 mm long, sometimes awned glumes that are shorter than to slightly longer than the lemmas, 0.7 - 1.7 mm long ligules, and 1.6 - 1.9 mm long caryopses. Muhlenbergia glabrifloris has 1.5 - 3.5 mm long, sometimes awned glumes that are shorter than or slightly longer than the lemmas, 0.5 - 1.5 mm long ligules, and 1.2 - 1.4 mm caryposes.

Flowering: July to October

Habitat and ecology: Rare in dry woods.

Occurence in the Chicago region: native

Etymology: Muhlenbergia is named after American botanist, Gotthilf Henry Ernest Muhlenberg (1753-1815). Sobolifera means sprout-bearing.

Author: The Morton Arboretum

Vigorously rhizomatous; culms arising singly or few together, erect, becoming much branched, the internodes glabrous; sheaths glabrous, frequently overlapping; blades stiff, 4-16 cm נ2-7 mm; ligule membranous, 0.5-1 mm, infls terminal or some on erect leafy lateral branches, included at base or more often exsert on slender erect peduncles to 11 cm; panicles very slender, arcuate, 5-15 cm נ2-4 mm, with short erect branches; spikelets whitish; glumes subequal, 1.3-2(-2.5) mm, shorter than the lemma, the margins usually sigmoid-curved; lemma 1.8-2.5 mm, awnless or with an awn-tip to 4 mm, the callus scantily bearded; anthers 0.4-0.8 mm; 2n=40. Dry upland woods or rocky outcrops; Mass. to Va., w. to Wis., Nebr. and Tex. (M. setigera, the awned, mainly western form)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.