Western Panicgrass

Panicum thermale Bolander, Proc. Calif. Acad. 2: 181. 1862
Vernal culms grayish-green, densely tufted, velvety-villous, 10-30 cm. high, ascending or spreading, the nodes with a dense ring of short hairs; leaf-sheaths often overlapping, velvetyvillous; ligule 3 mm. long; blades thick, ascending or spreading, 3-8 cm. (mostly about 5 cm.) long, 5-12 mm. wide, acuminate, rounded or a^bcordate at base, both surfaces densely velvety-villous; panicles exserted or at high altitudes partly included, 3-6 cm. long, about as wide, densely flowered, the axis villous, the flexuous branches spreading, often drooping; spikelets 1.9-2 mm. long, 1 mm. wide, obovate-oblong, obtuse, turgid, papillose-pilose; first glume about one third the length of the spikelet, obtuse or abruptly pointed ; second glume and sterile lemma subequal, the glume shorter than the fruit at maturity; fruit 1.7 mm. long, 1 mm. wide, elliptic, subobtuse.
Autumnal phase widely spreading, the branches appearing even before the primary panicles are exserted, repeatedly branching, the whole forming a dense cushion, the blades and panicles of the ultimate branchlets reduced; winter rosette appearing early, the blades ovatelanceolate, usually less pubescent than those of the culms.
Type) locality: Sonoma County, California. Distribution: Alberta to Wyoming and California.

Panicum albemarlense Ashe, Jour. Elisha Mitchell Soc. 16: 84
1900.
Panicum velutinum Bosc; Spreng. Syst. 1: 315, as synonym. 1825. Not P. velutinum G. Meyer, 1818.
Vernal phase olivaceous; culms cespitose, 25-45 cm. high, slender, at first erect or ascending, soon becoming geniculate at the lower nodes and more or less spreading; culms, leafsheaths, and blades grayishvillous, the blades 4.5-7 cm. long, 3-6 mm. wide, ascending, the upper surface puberulent as well as longvillous ; panicles 3-5 cm. long, about as wide, more
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densely flowered than P. meridionale, the axis puberulent, the branches ascending; spikelets 1.4 mm. long, 0.9 mm. wide, blunt and turgid, pilose; first glume about two fifths the length of the spikelet; second glume and sterile lemma subequal, the glume scarcely equaling the fruit at maturity; fruit 1.25 mm. long, 0.9 mm. wide, obtuse.
Autumnal phase widely decumbent-spreading or ascending, freely branching at all but the uppermost nodes, the branches narrowly ascending, the reduced, flat blades mostly exceeding the panicles.
Type locality: Scranton, North Carolina.
Distribution: Connecticut to North Carolina; .around the southern end of I^ake Michigan.

Panicum huachucae Ashe, Jour. Elisha Mitchell Soc. IS: 51
1898.
Panicum nitidum pilosum Torr. Fl. U. S. 146. 1824. Not P. pilosum Sw. 1788. ? Panicum iowense Ashe, Bull. N. Car. Exp. Sta. 175: 175. 1900. Panicum lanuginosum Huachucae Hitchc. Rhodora 8: 208. 1906.
Vernal phase cespitose, usually stiffly upright, light-olivaceous, often purplish, harsh to the touch from the copious, spreading, papillose pubescence of culms and leaves; culms 20-60 cm. high; nodes bearded with spreading hairs; leaf-sheaths shorter than the internodes; ligule 3-4 mm. long; blades firm, stiffly erect or ascending, 4r-8 cm. long, 6-8 mm. wide, the veins inconspicuous, the upper surface copiously short-pilose, especially toward the base, the lower surface densely pubescent; panicles rather short-exserted until maturity, 4-6 cm. long, nearly as wide, rather densely flowered, the axis and often the branches pilose, the flexuous, fascicled branches ascending or spreading, with short spikelet-bearing branchlets at base of the fascicles; spikelets 1.6-1.8 mm. long, 1 mm. wide,' obovate, obtuse, turgid, papillose-pubescent; first glume about one third the length of the spikelet; second glume and sterile lemma subequal, scarcely covering the fruit at maturity; fruit 1.5-1.6 mm. long, 1 mm. wide, elliptic, obscurely apiculate. .tart 5, iviDj .ruAC-t^AiS zoy
Autumnal phase stiffly erect or ascending, the culms and sheaths sometimes papillose
only, the branches fascicled, the reduced, crowded leaves ascending, the blades 2-3 cm. long,
much exceeding the reduced panicles.
Type locality: Huachuca Mountains, Arizona. *
Distribution: Maine to South Dakota, and south to North Carolina and Arizona.

Panicum auburne Ashe, Bull. N. Car. Exp. Sta. 175: 115
1900,
Vernal phase grayish velvety-villous throughout; culms tufted, 20-50 cm. high, geniculate at base, widely spreading, soon becoming branched and decumbent, rather slender, densely papillose-silkyvillous below, velvety with copious silky hairs intermixed above; leaf -sheaths usually abbut half the length of the internodes, villous like the culms; ligule 3-4 mm. long; blades rather thin, ascending, 3-7 cm. long, 3-5 mm. wide, acuminate, slightly narrowed toward the base, the upper surface velvety with copious long, silky hairs intermixed, especially toward the base, the lower surface silkyvillous or velvety, the nerves somewhat conspicuous ; panicles short-exserted, 3-5 cm. long, about as wide, the axis velvety, with long, silky hairs intermixed, the flexuous branches ascending or spreading; spikelets 1.3-1.4 mm. long, 0.8-0.9 mm. wide, obovate, very turgid, densely papillose-pubescent; first glume one third to half the length of the spikelet, acute; second glume and sterile lemma equal and covering the fruit at maturity; fruit 1.1-1.2 mm. long, 0.8 mm. wide, obovate-elliptic, minutely pointed.
Autumnal phase early becoming diffusely branched at all the nodes, prostrate-spreading, forming large mats, the branches curved upward at the ends ; earlier branches longer than the primary internodes, the ultimate branchlets in short fascicles with involute-pointed blades 1-2 cm. long, the numerous turgid little spikelets clustered at their bases; winter rosette appearing rather late, the lanceolate blades silky-villous like those of the primary culm.
Type locality: Auburn, Alabama.
Distribution: Virginia to Florida, and west to Louisiana.

Panicum languidum Hitchc. & Chase, Contr. U. S. Nat. Herb
15: 232. 1910.
Panicum unciphyllum f. prostratum Scribn. & Merr. Rhodora 3: 124. 1901. Not P. prostratum Lam. 1791.
Vernal phase tufted; culms 25-40 cm. high, weak, slender, ascending or spreading, pilose; leaf -sheaths shorter than the internodes, papillose-pilose; ligule about 3 mm. long; blades thin, lax, ascending or spreading, 4-7 cm. long, 4-9 mm. wide, acuminate, slightly narrowed to the rounded base, sparsely pilose on the upper surface, minutely appressed-pubescent beneath, usually with long hairs intermixed; panicles rather long-exserted, 3-6 cm. long, two thirds to three fourths as wide, loosely flowered, the very flexuous branches finally spreading or drooping, the spikelets on long, mostly divaricate, flexuous pedicels, the axis and branches sparsely longpilose; spikelets 2 mm. long, 1 mm. wide, elliptic, acute, pilose; first glume about one third the length of the spikelet, obtuse or acute ; second glume and sterile lemma exceeding the fruit and slightly pointed beyond it; fruit 1.5 mm. long, 1 mm. wide, obtuse.
Autumnal phase decumbent, with geniculate, sometimes rooting nodes, branching from all the nodes, the early branches nearly equaling the primary culm, repeatedly branching, forming a large, loose straggling clump, the ultimate blades and panicles scarcely reduced.
Type locality: South Berwick, Maine. Distribution : Maine, Massachusetts, and New York.

Panicum shastense Scribn. & Merr. Circ. U. S. Dep. Agr
Agrost. 35: 3. 1901.
Vernal phase pale-green; culms tufted, 30-50 cm. high, slender, ascending from a more or less geniculate base, papillose-pilose with ascending hairs; nodes short-bearded; leaf -sheaths papillose-pilose, the hairs spreading; hairs of the ligule rather sparse, 2-3 mm. long; blades ascending, 6-8 cm. long, 6-8 mm. wide, acuminate, scarcely narrowed toward the base, papillose-pilose on the. under surface and with scattered long hairs on the upper ; panicles shortexserted, 6-8 cm. long, about two thirds as wide, the axis pilose, the flexuous branches ascending; spikelets 2.4—2.6 mm. long, 1.2-1.4 mm. wide, obovate-oblong, obtuse, papillose-pubescent ; first glume one fourth to one third as long as the spikelet, pointed; second glume scarcely equaling the fruit and sterile lemma; fruit 2.1 mm. long, 1.3 mm. wide, elliptic.
Autumnal phase spreading, with geniculate nodes and elongate, arched internodes, rather
sparingly branching from the middle nodes, the primary branches elongate, the ultimate
branchlets shorter than the internodes.
Type locality: Castle Crag, California. Distribution: Known only from the type locality.

Panicum scoparioides Ashe, Jour. Elisha Mitchell Soc. IS: 53
1898.
Vernal plants light-green; culms few to several in a tuft, 30-50 cm. high, slender, erect or ascending, sparsely papillose-hispid with ascending hairs or nearly glabrous, the upper internodes shortened; nodes sometimes sparsely bearded; leaf-sheaths papillose-hispid to nearly glabrous, the lower distant, the upper approximate, sometimes overlapping; ligule 2-3 mm. long; blades firm, ascending, 7-10 cm. long, 6-10 mm. wide, tapering to the rounded base, acuminate," appressed-pubescent beneath, sparsely hispid on the upper surface, usually a few long hairs at the base ; panicles short-exserted, usually included at the base until maturity, rather densely flowered, 4-7 cm. long, about two thirds as wide, the branches ascending; spikelets 2.2-2.3 mm. long, 1.2 mm. wide, obovate, obtuse or minutely pointed; first glume about one fourth as long as the spikelet, subacute ; second glume and sterile lemma papillose-pubescent, strongly nerved, subequal, as long as the fruit, the m argins at the summit usually inrolled, the midnerve produced into an apiculus; fruit 1.9 mm. long, 1.1 mm. wide, elliptic.
Autumnal phase erect or spreading; culms sparingly branching from the upper and middle nodes after the maturity of the primary panicle, the stiff, reduced" blades involute-pointed, much exceeding the panicles.
Type locality: Centreville, Delaware.
Distribution: Vermont to Delaware; Minnesota; Indiana.

Panicum implicatum Scribn. Bull. U. S. Dep. Agr. Agrost. 11:
43. 1898.
Panicum unciphyllum implicatum Scribn. & Merr. Rhodora 3: 123. 1901.
Vernal phase with tufted, slender culms 20-55 cm, high, erect or ascending, papillosepilose with spreading hairs; leaf-sheaths shorter than the internodes, papillose-pilose; ligule 4r-5 mm. long; blades firm, erect or ascending, 3-6 cm. long, 3-6 mm. wide, rarely longer or wider, more or less involute-acuminate, the upper surface pilose with erect hairs 3-4 mm. long, the lower surface papillose-pubescent with subappressed hairs; primary panicles long-exserted, pyramidal in outline, 3-6 cm. long, about as wide, the axis long-pilose, the branches flexuous, in typical specimens tangled and the lower drooping; spikelets 1.5 mm. long, 0.9 mm. wide, obovate, obtuse, papillose-pilose; first glume about one fourth the length of the spikelet, obtuse; second glume and sterile lemma equaling the fruit at maturity; fruit 1.3 mm. long, 0.9 mm. wide, broadly elliptic, obtuse, very minutely umbonate.
Autumnal phase erect or spreading, rather loosely branching from the lower and middle nodes, the primary culms becoming more or less geniculate below; leaves and panicles reduced; winter leaves lanceolate-ovate, pilose above, the rosette appearing late.
Type locality: Cape Elizabeth, Maine. Distribution: Nova Scotia to Iowa.

Panicum tennesseense Ashe, Jour. EHsha Mitchell Soc. 15: 52
1898.
"Vernal phase suberect or stiffly spreading, bluish-green, often purplish; culms 25-60 cm.
high, slender, papillose-pilose, or the upper portion glabrous ; leaf -sheaths spreading-pubescent,
rarely nearly glabrous; ligule dense, 4—5 mm. long; blades firm with a thin white cartilaginous
margin, ascending or suberect, 6-9 cm. long, 5-8 mm., rarely 10 mm. wide (the upper smaller),
often sparsely ciliate at base, the veins usually conspicuous, the upper surface glabrous or with
a few long, scattered hairs toward the base, the lower surface appressed-pubescent or nearly
glabrous; panicles 4-7 cm. long, nearly as wide, rather densely flowered, the lower branches
ascending; spikelets 1.6-1.7 mm. long, 0.8-1 mm. wide, obovate-obtuse, turgid, pubescent;
first glume about one fourth the length of the spikelet ; second glume shorter than the sterile
lemma, leaving the summit of the fruit exposed at maturity; fruit 1.4 mm. long, 0.8 mm. wide,
elliptic, obtuse.
Autumnal phase widely spreading or decumbent, with numerous fascicled, somewhat
flabellate, branches, often forming prostrate mats; leaves much reduced, the blades usually
ciliate at base; winter rosette formed early.
Tyfb locality : La Vergne County, Tennessee.
Distribution: Maine to Minnesota, and south to Alabama and Arizona; Vera Cruz.

Panicum pseudopubescens Nash, Bull. Torrey Club 26: 577
1899.
Vernal phase similar to that of P. villosissimum; culms somewhat stiffer, the pubescence more silky, appressed on the culms, ascending on the leaf-sheaths; ligule 2-3 mm. long; blades somewhat firmer, the pubescence on the upper surface short like that on the lower and sparse or wanting down the center or the upper surface occasionally glabrous; panicles averaging larger, the spikelets not so long-pediceled; spikelets 2.25-2.4 mm. long, 1.1 mm. wide, obovateelliptic, obtuse, or slightly pointed; the pubescence as in P. villosissimum; second glume slightly shorter than the fruit at maturity; fruit 1.9 mm. long, 1 mm. wide, elliptic, subacute.
Autumnal phase usually stiffly spreading, sometimes prostrate; culms sparingly branching from the lower and middle nodes after the maturity of the primary panicle, less freely branching than in P. villosissimum; upper surface of the reduced blades usually glabrous except along the margins and at the base; winter leaves as in P. villosissimum.
Type i,ocauty: Auburn, Alabama.
Distribution : Connecticut to Illinois, and south to Florida and Mississippi ; San Luis Potost

Panicum praecocius Hitchc. & Chase; Hitchc. Rhodora
8: 206. 1906.
Vernal culms tufted, 15-25 cm. high, early branching and elongating, sometimes to 45 cm., at first erect, soon becoming geniculate and spreading, very slender, wiry, abundantly papillose-pilose with weak spreading hairs 3-4 mm. long; leaf -sheaths, even the lowest, much shorter than the very long internodes, those of the branches usually but 1-2 cm. long, pilose like the culm, more prominently papillose; ligule 3-4 mm. long; blades rather firm, erect or ascending, 5-9 cm. long, 4-6 mm. wide, the margins parallel about two thirds their length, acuminate, long-pilose on both surfaces, the hairs of the upper surface 4^5 mm. long, erect from the plane of the blade, the under surface prominently papillose; panicles at first usually overtopped by the upper leaf, but at or past maturity exserted, 4-6 cm. long, about as wide, loosely flowered, the axis pilose, the branches flexuous, spreading or ascending; spikelets 1.8-1.9 mm. long, 1 mm. wide, obovate, turgid, obtuse, pilose; first glume one third to half the length of the spikelet, .triangular ; second glume and sterile lemma subequal, the glume slightly shorter than the fruit at maturity; fruit 1.6 mm. long, 1 mm. wide, broadly elliptic.
Autumnal phase ascending from a geniculate base, or in prairie sod erect, forming close bunches 10-20 cm. high, the upper portion of the primary culms early deciduous, the branches appressed, the scarcely reduced blades erect or narrowly ascending, much exceeding the reduced panicles; winter rosette appearing late, the blades 2-3 cm. long, long-pilose.
Type locality: Wady Petra, Illinois.
Distribution: Michigan to Minnesota and eastern Texas.

Panicum thurowii Scribn. & Smith; Scribn. Circ. U. S. Dep
Agr. Agrost. 16: 5. 1899.
Vernal form bluish-green, but drying olive; culms tufted, 35-70 cm. high, erect or ascending, villous, the nodes bearded with spreading hairs, usually a glabrous ring below; leaf -sheaths long, the lower often overlapping, the upper shorter than the internodes, sparsely or rather densely villous; ligule 4 mm. long; blades rather stiff, ascending or spreading, 7-12 cm. long, or the uppermost only 2-3 cm. long, 6-10 mm. wide, acuminate, often somewhat involute toward the apex, narrowed toward the rounded base, the upper surface sparingly pilose toward 261
the base and margins, the lower surface densely vel vety-villous ; panicles short-exserted, 7-11 cm. long, nearly as wide, rather densely flowered, the axis sparingly villous near the base, the branches spreading; spikelets 2 mm. long, 1 mm. wide, elliptic, somewhat obovate at maturity, obtuse, pubescent with soft, spreading hairs; first glume one fifth the length of the spikelet, obtuse or obscurely pointed; second glume and sterile lemma equal, scarcely equaling the fruit at maturity, obtuse or slightly pointed; fruit 1.7 mm. long, 1 mm. wide, elliptic, subacute.
Autumnal form erect, after the maturity of the primary panicle bearing at the middle nodes a few appressed or ascending fascicled branches scarcely longer than the primary internodes, the reduced blades flat or somewhat involute at the tips, ciliate.
Type locality: Waller County, Texas. Distribution : Southern Alabama to eastern Texas

Panicum meridionale Ashe, Jour. Elisha Mitchell Soc. 15: 59
1898.
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Panicum filiculme Ashe, Jour. Elisha Mitchell Soc. 15: 59. 1898.
? Panicum microphyllum Ashe, jour. Elisha Mitchell Soc. 15: 61. 1898.
Panicum unciphyllum meridionale Scribn. & Merr. Rhodora 3: 123. 1901.
Vernal phase tufted; culms 15-40 cm. high, pilose below, the upper portion and the axis of the panicle appressed-pubescent, or the latter often nearly glabrous; lower leaf -sheaths pilose, upper minutely appressed-pubescent; ligule 3-4 mm. long; blades 1.5-4 cm. long, 2-4 mm. wide, long-pilose on the upper surface, the hairs erect, less dense than in P. implicatum; panicles 1.5-4 cm. long, nearly or quite as wide, ovate or rhombic, the branches ascending; spikelets 1.3-1.4 mm. long, 0.8 mm. wide, obovate, obtuse, minutely papillose-pubescent; first glume one fourth to one third the length of the spikelet, acute or subacute; second glume and sterile lemma equal, as long as the fruit at maturity; fruit 1.2 mm. long, 0.8 mm. wide, broadly elliptic, obscurely pointed.
Autumnal phase erect or nearly so, with fascicled branchlets from all the nodes; leaves and panicles not greatly reduced, the latter included late in the season ; winter leaves lanceolate, long-pilose toward the base, the rosette formed rather late.
Type locality: Chapel Hill, North Carolina.
Distribution: Rhode Island to Wisconsin, and south to Alabama.

Perennials, Terrestrial, not aquatic, Rhizomes present, Stems nodes swollen or brittle, Stems erect or ascending, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem nodes bearded or hairy, Plants conspicuously hairy, grayish, or wooly, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath hairy, hispid or prickly, Leaf sheath hairy at summit, throat, or collar, Leaf sheath and blade differentiated, Leaf blades lanc eolate, Leaf blades ovate, Leaf blades 2-10 mm wide, Leaf blades 1-2 cm wide, Leaf blades mostly flat, Leaf blades more or less hairy, Ligule present, Ligule a fringe of hairs, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence a contracted panicle, narrowly paniculate, branches appressed or ascending, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence branches more than 10 to numerous, Flowers bisexual, Spikelets pedicellate, Spikelets dorsally compressed or terete, Inflorescence or spikelets partially hidden in leaf sheaths, subtended by spatheole, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets with 2 florets, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating below the glumes, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes d istinctly unequal, Glumes equal to or longer than adjacent lemma, Glume equal to or longer than spikelet, Glumes 3 nerved, Glumes 4-7 nerved, Lemma similar in texture to glumes, Lemma coriaceous, firmer or thicker in texture than the glumes, Lemma becoming indurate, enclosing palea and caryopsis, Lemma 3 nerved, Lemma 5-7 nerved, Lemma 8-15 nerved, Lemma glabrous, Lemma apex truncate, rounded, or obtuse, Lemma awnless, Lemma margins inrolled, tightly covering palea and caryopsis, Lemma straight, Palea present, well developed, Palea about equal to lemma, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis.

Dichanthelium lanuginosum is a species of rosette grass native to North America. It is most common in the central and eastern United States. It is found in a variety of habitats, mostly in open, dry areas.

A variety, D. lanuginosum var. thermale, grows in geothermal areas of Yellowstone National Park, United States. It is able to withstand high temperatures and high acidity in its rhizosphere. In 2007 it was found that the heat tolerance is conferred to the grass by a symbiosis between a fungus and a virus. When it is colonised by the fungus Curvularia protuberata and the fungus is in turn colonised by a particular virus, the grass is able to tolerate soil temperatures of up to 65 °C that would otherwise be lethal. Due to the distinctiveness and isolation of this taxon, it is sometimes considered to be a separate species: Dichanthelium thermale.