26.15   ANDROPOGON L.
Christopher S. Campbell

Plants perennial; usually cespitose, sometimes rhizomatous. Culms 20-310 cm, erect, much-branched distally. Leaves not aromatic; ligules membranous, sometimes ciliate; blades linear, flat, folded, or convolute. Inflorescences terminal and axillary or a false panicle; inflorescence units 1-600+ per culm; peduncles initially concealed by the subtending leaf sheaths, sometimes exserted beyond the sheaths at maturity, with (1)2-5(13) rames; rames not reflexed at maturity, axes slender, terete to flattened, not longitudinally grooved, usually conspicuously pubescent, with spikelets in heterogamous sessile-pedicellate pairs (the terminal spikelets sometimes in triplets of 1 sessile and 2 pedicellate spikelets), apices of the internodes neither cupulate nor fimbriate; disarticulation in the rames, below the sessile spikelets. Sessile spikelets bisexual, awned, with short, blunt calluses; lower glumes 2-keeled, flat or concave, usually not veined between the keels, sometimes 2-9-veined; anthers 1, 3(2). Pedicels usually longer than 3 mm, similar to the rame internodes in shape, length, and pubescence color, not fused to the rame axes. Pedicellate spikelets usually vestigial or absent, sometimes well-developed and staminate. x = 10. Name from the Greek andro, man, and pogon, beard, referring to the pubescent pedicels of the staminate spikelets.

Andropogon is a cosmopolitan genus of tropical and temperate zones, comprising approximately 120 species. Thirteen species are native to the Flora region. Andropogon bicornis has been found in the region, but is not known to be established. All but A. hallii grow in the southeastern United States.

Several taxa are ecologically important in North America. Andropogon gerardii is one of the most important native grasses in North America, being one of the dominant species in the tallgrass prairies that used to cover the center of the continent. Many varieties of A. glomeratus and A. virginicus aggressively colonize abandoned fields, cutover timberlands, and roadsides. Some species are used in restoration and landscaping.

Species of Andropogon with solitary rames are easily confused with Schizachyrium but, in Andropogon, the lower glumes of the sessile spikelets are flat or concave and the rame internodes are not cupulate, whereas Schizachyrium has convex glumes and rame internodes with strongly cupulate apices. Successful identification of species in Andropogon sect. Leptopogon (numbers 3-14) requires mature, complete specimens and careful field study (Campbell 1983, 1986).


SELECTED REFERENCES Barnes, P.W. 1986. Variation in the big bluestem (Andropogon gerardii)-sand bluestem (Andropogon hallii) complex along a local dune/meadow gradient in the Nebraska sandhills. Amer. J. Bot. 73:172-184; Campbell, C.S. 1983. Systematics of the Andropogon virginicus complex (Gramineae). J. Arnold Arbor. 64:171-254; Campbell, C.S. 1986. Phylogenetic reconstructions and two new varieties in the Andropogon virginicus complex (Poaceae: Andropogoneae). Syst. Bot. 11:280-292; Clayton, W.D. 1964. Studies in the Gramineae: V. New species of Andropogon. Kew Bull. 17:465-470.

1
Pedicellate spikelets usually well-developed, (3.5)6-12 mm long, usually staminate; sessile spikelets 5-12 mm long (sect. Andropogon) (2)
Pedicellate spikelets usually vestigial or absent, those of the terminal spikelet units occasionally well-developed and staminate; sessile spikelets 2.6-8.4 mm long (sect. Leptopogon) (3)
2
Sessile spikelets with awns 8-25 mm long; ligules 0.4-2.5 mm long; hairs of the rame internodes 2.2-4.2 mm long, sparse to dense; rhizomes sometimes present, the internodes usually less than 2 cm .... 1. A. gerardii
Sessile spikelets unawned or with awns less than 11 mm long; ligules (0.9)2.5-4.5 mm long; hairs of the rame internodes 3.7-6.6 mm long, usually dense; rhizomes always present, the internodes often more than 2 cm long ..... 2. A. hallii
3
Peduncles with solitary rames; plants of southern Florida ..... 3. A. gracilis
Peduncles with (1)2-13 rames; plants of varied distribution, including southern Florida (4)
4
Rames not or scarcely exserted at maturity; peduncles mostly less than 15 mm long at maturity (5)
Rames sometimes exserted above their subtending sheaths at maturity; 1 or more peduncles more than 15 mm long at maturity (8)
5
Culms 30-140 (usually about 80) cm tall; blades 0.8-5 (usually about 2.5) mm wide; inflorescence units 2-31 per culm ..... 9. A. gyrans
Culms 20-250 (usually more than 90) cm tall; blades 1.7-9.5 (usually more than 3) mm wide; inflorescence units 3-600 per culm (6)
6
Blades pubescent, most hairs appressed; callus hairs 1.5-5 mm long ..... 13. A. longiberbis
Blades glabrous or with spreading (rarely appressed) hairs; callus hairs 1-3 mm long (7)
7
Blades 11-52 cm long; sheaths smooth, rarely somewhat scabrous; ligules 0.2-1 mm long; keels of the lower glumes usually smooth below midlength, scabrous distally ..... 12. A. virginicus
Blades 13-109 cm long; sheaths usually scabrous; ligules 0.6-2.2 mm long; keels of the lower glumes sometimes scabrous below midlength ..... 14. A. glomeratus
8
Anthers 3 (9)
Anthers 1 (rarely 3) (10)
9
Sessile spikelets 4.5-8.4 mm long; pedicellate spikelets 1.5-3.6 mm long, sterile; plants common and widespread in the southeastern United States ..... 4. A. ternarius
Sessile spikelets 3-4 mm long; pedicellate spikelets mostly vestigial or absent, those of the terminal spikelet units well-developed and staminate; in the Flora region, known only from southern Florida ..... 5. A. bicornis
10
Peduncles with 2-13 rames ..... 8. A. liebmannii
Peduncles usually with 2 (infrequently up to 4) rames or (in A. gyrans var. gyrans and A. virginicus var. virginicus), 2-5 (infrequently up to 7) rames (11)
11
Culms 30-120(140) (usually less than 100) cm tall; blades 0.8-5 (usually less than 3) mm wide; inflorescence units 2-31 per culm (12)
Culms (20)90-310 (usually more than 100) cm tall; blades 1.7-9.5 (usually more than 3) mm wide; inflorescence units 5-210 per culm (13)
12
Peduncles with 2-5 rames; anthers 0.6-1.7 mm long; sessile spikelets (3)4.1-4.4(5.7) mm long ..... 9. A. gyrans
Peduncles with 2 rames; anthers 1.2-2 mm long; sessile spikelets (4)4.8-5(5.5) mm long ..... 10. A. tracyi
13
Upper portion of the plants open, the branches conspicuously arching ..... 11. A. brachystachyus
Upper portion of the plants dense, the branches usually straight and erect to ascending (14)
14
Rame internodes usually densely and uniformly pubescent over their entire length; anthers 1.3-3.5 mm long; sessile spikelets (3.8)4-6.1 mm long (15)
Rame internodes sparsely pubescent basally, more densely pubescent distally; anthers 0.5-1.5 mm long; sessile spikelets 2.6-4(5) (16)
15
Blades 15-35 cm long, often more or less pubescent; sheaths smooth, very rarely somewhat scabrous; anthers 2-3.5 mm long; inflorescence units 5-45 per culm ..... 6. A. arctatus
Blades 32-61 cm long, usually glabrous; sheaths often scabrous; anthers 1.3-2 mm long; inflorescence units usually at least 50 (9-210) per culm ..... 7. A. floridanus
16
Blades 11-52 cm long; sheaths smooth, rarely somewhat scabrous; ligules 0.2-1 mm long; keels of the lower glumes usually smooth below midlength, scabrous distally ..... 12. A. virginicus
Blades 13-109 cm long; sheaths usually scabrous, sometimes smooth; ligules 0.6-2.2 mm long; keels of the lower glumes sometimes scabrous below midlength ..... 14. A. glomeratus


Andropogon L. sect. Andropogon

Inflorescences usually only terminal, axillary inflorescences absent or few. Lower glumes thinly coriaceous, with 3-9 veins between the keels; keels often winged. Pedicellate spikelets usually well-developed, staminate.


1.   Andropogon gerardii Vitman
Big Bluestem, Barbon de Gerard

Plants often forming large clumps, rhizomes, if present, with internodes shorter than 2 cm. Culms 1-3 m, often glaucous. Sheaths glabrous or pilose; ligules 0.4-2.5 mm; blades 5-50 cm long, (2)5-10 mm wide, usually pilose adaxially, at least near the collar. Inflorescence units usually only terminal; peduncles with 2-6(10) rames; rames 5-11 cm, exserted at maturity, usually purplish, sometimes yellowish; internodes sparsely to densely pubescent, hairs 2.2-4.2 mm, usually white, rarely yellowish. Sessile spikelets 5-11 mm, scabrous; awns 8-25 mm; anthers 3, 2.5-4.5 mm. Pedicellate spikelets 3.5-12 mm, usually well-developed and staminate. 2n = 20, 40, 60 (usually), 70, 80, 90.

Andropogon gerardii grows in prairies, meadows, and generally dry soils. It is a widespread species, extending from southern Canada to Mexico, and was once dominant over much of its range. It is frequently planted for erosion control, restoration, or as an ornamental; the records from Washington and central Montana reflect such plantings. It hybridizes with A. hallii, the two sometimes being treated as conspecific subspecies.


2.   Andropogon hallii Hack.
Sand Bluestem

Plants strongly rhizomatous, rhizome internodes often longer than 2 cm. Culms (40)60-150(200) cm, strongly glaucous. Ligules (0.9)2.5-4.5 mm, ciliate; blades 3-40(51) cm long, (1.5)2-10 mm wide, often pilose, at least near the collar. Inflorescence units usually only terminal; peduncles with 2-7 rames; rames 4-7(9) cm, exserted at maturity; internodes usually densely pubescent, hairs 3.7-6.6 mm, often strongly yellowish. Sessile spikelets (5)6.5-12 mm; lower glumes often ciliate; awns absent or to 11 mm; anthers 3, (2.3)4-6 mm. Pedicellate spikelets 3.5-12 mm, usually well-developed and staminate. 2n = 60 (usually), 70, 100.

Andropogon hallii grows on sandhills and in sandy soil. Its range extends through the central plains into northern Mexico. It is similar to A. gerardii, differing primarily in its rhizomatous habit, more densely pubescent rames and pedicels, and greater drought tolerance. Andropogon hallii and A. gerardii are sympatric in some locations. The two species can hybridize and are sometimes treated as conspecific subspecies.


Andropogon sect. Leptopogon Stapf

Inflorescences false panicles; inflorescence units numerous. Lower glumes membranous; keels not winged, intercostal region usually not veined or with inconspicuous veins. Pedicellate spikelets usually vestigial or absent.


3.   Andropogon gracilis Spreng.
Wire Bluestem

Plants densely cespitose. Culms 20-60 cm, wiry, glabrous. Sheaths smooth; ligules to 1.4 mm; blades to 45 cm long, to 4 mm wide, involute and filiform, or folded. Inflorescence units 3-50+ per culm; peduncles 2-13.2 cm, with 1 rame; rames 2-4 cm, usually long-exserted at maturity; internodes densely pubescent, hairs to 8 mm. Sessile spikelets 4-6 mm; lower glumes scabrous in the distal 1/2; awns 11-20 mm. Pedicellate spikelets reduced to an awned or unawned glume, sterile. 2n = 40.

Andropogon gracilis grows on oölite in openings and rocky margins of pine woodlands of southern Florida and the West Indies. Although not uncommon, it is frequently overlooked. It has sometimes been placed in Schizachyrium because of its solitary rames.


4.   Andropogon ternarius Michx.
Split Bluestem

Plants cespitose. Culms 70-150 cm. Sheaths smooth or scabrous, sometimes pilose; ligules 0.4-1.5 mm, ciliate; blades 1-3 mm wide, pubescent or glabrous and glaucous. Inflorescence units 2-30+ per culm; peduncles usually 5-20 mm, with (1)2 rames; rames 3-4 cm, exserted at maturity, terminating in a sessile-pedicellate spikelet pair; internodes sparsely to densely villous, hairs from as long as to twice as long as the sessile spikelets. Sessile spikelets 4.5-8.4 mm; callus hairs to 8 mm; awns 10-25 mm; anthers 3, 1.2-2.3 mm. Pedicellate spikelets 1.5-3.6 mm, sterile. 2n = 40, 60.

Andropogon ternarius grows in the southeastern United States and northern Mexico. It is planted as an ornamental and for erosion control on slopes in poor and sandy soils, and is tolerant of coastal conditions.

Andropogon ternarius is similar to A. arctatus, but differs in its possession of three anthers and usually in its longer spikelets, both sessile and pedicellate.

1
Rames densely villous, with hairs about twice as long as the sessile spikelets and more or less obscuring them; lower glumes of the sessile spikelets sometimes scabrous, without conspicuous veins between the keels ..... var. cabanisii
Rames sparsely villous, with hairs about as long as the sessile spikelets, but not obscuring them; lower glumes of the sessile spikelets scabrous, often conspicuously 2-veined between the keels ..... var. ternarius


Andropogon ternarius var. cabanisii (Hack.) Fernald & Griscom

Rames densely villous; internode hairs about twice as long as and more or less obscuring the sessile spikelets. Lower glumes of sessile spikelets glabrous, sometimes scabrous, not conspicuously veined between the keels.

Andropogon ternarius var. cabanisii grows in dry pine woods and scrublands of peninsular Florida.


Andropogon ternarius Michx. var. ternarius

Rames sparsely villous; internode hairs about as long as, but not obscuring, the sessile spikelets. Lower glumes of sessile spikelets scabrous, often with 2 conspicuous veins between the keels.

Andropogon ternarius var. ternarius grows in dry, sandy woods, fields, openings, and roadsides of the southeastern United States and Mexico.


5.   Andropogon bicornis L.
Barbas de Indio

Plants densely cespitose, upper portion dense, obovate to obpyramidal. Culms60-250 cm; internodes not glaucous. Sheaths smooth; ligules 0.6-1 mm; blades 20-70 cm long, 2-7 mm wide, usually glabrous or scabrous on the margins. Inflorescence units 50-500; subtending sheaths 2.5-4.5 cm long, 2-3 mm wide; peduncles 20-70 mm, with 2(3) rames; rames 2-4 cm, exserted at maturity; internodes filiform, densely and evenly pubescent, hairs 3-9 mm. Sessile spikelets 3-4 mm; unawned; callus hairs 0.5-1 mm; keels of lower glumes scabrous above the midpoint; anthers 3, 1-1.4 mm. Pedicellate spikelets mostly vestigial or absent, 1-2 of those in the terminal units on each rame 3-5 mm and staminate. 2n = 60, 120.

Andropogon bicornis is a widespread species of the Western Hemisphere tropics. It was collected in the early 1960s in Dade County, Florida, near the track of a major hurricane, but may not be established in the Flora region.


6.   Andropogon arctatus Chapm.
Pinewoods Bluestem

Plants cespitose or somewhat rhizomatous, upper portion dense, oblong to ovate. Culms 90-170 cm; internodes occasionally somewhat glaucous just below the nodes; branches straight, erect to ascending. Sheaths smooth, rarely somewhat scabrous; ligules 0.3-0.9 mm, sometimes ciliate, cilia to 0.5 mm; blades 15-35 cm long, 3-8 mm wide, glabrous or densely pubescent, hairs spreading. Inflorescence units 5-45 per culm; subtending sheaths (3.3)3.8-6.8(9) cm long, (2.5)3.2-4(5) mm wide; peduncles (9)26-66(115) mm, with 2(4) rames; rames (2.2)2.6-4.3(5.3) cm, usually exserted at maturity, pubescence either evenly distributed or more dense distally within each internode. Sessile spikelets (4.3)4.9-5.4(6.1) mm; callus hairs 1.5-2.5 mm; keels of lower glumes scabrous from below the midpoint; awns 5-16 mm; anthers 1(3), 2-3.5 mm, red. Pedicellate spikelets vestigial or absent. 2n = 20.

Andropogon arctatus grows in flatwoods, bogs, and scrublands of southern Alabama and Florida. Its flowering appears to be stimulated by fire but, unlike other members of sect. Leptopogon in the Flora region, the effect lasts only one or two years, the plants then remaining vegetative until the next fire occurs. It is similar to A. ternarius, but differs in its long, usually solitary anther and shorter spikelets.


7.   Andropogon floridanus Scribn.
Florida Bluestem

Plants cespitose, usually densely obpyramidal to oblanceolate above. Culms 70-210 cm; internodes occasionally somewhat glaucous just below the node; branches straight, mostly erect to ascending. Sheaths often scabrous, sometimes smooth; ligules 0.4-1.2 mm, ciliate, cilia 0.2-1.3 mm; blades 32-61 cm long, 2.9-5 mm wide, glabrous, rarely sparsely pubescent. Inflorescence units (9)50-210 per culm; subtending sheaths (3)4-5.9(7) cm long, (1.5)2-2.7(3.6) mm wide; peduncles (10)19-48(93) mm, with 2(4) rames; rames (2)2.5-3.7(4.5) cm, usually exserted at maturity, internodes evenly pubescent. Sessile spikelets (3.8)4.4-4.8(5.5) mm; callus hairs 1-3 mm; keels of lower glumes glabrous below midlength; awns 5-15 mm; anthers 1(3), 1.3-2 mm, usually yellow (sometimes purple). Pedicellate spikelets vestigial or absent. 2n = 20.

Andropogon floridanus grows on sandy soils in southeastern Georgia and Florida, being most abundant in Pinus clausa scrublands. It usually occurs in small stands, but stands of about a hundred individuals have been observed.


8.   Andropogon liebmannii Hack.
Liebmann's Bluestem, Mohr's Bluestem

Plants cespitose, cylindrical to oblong above. Culms 20-170 cm; internodes not glaucous; branches mostly erect, straight. Sheaths smooth; ligules 0.7-1.2 mm, sometimes ciliate, cilia to 0.4 mm; blades 3-35 cm long, 2.5-7.5 mm wide, sparsely to densely pubescent with spreading, shaggy hairs. Inflorescence units 7-50 per culm; subtending sheaths (4)4.9-7.4(10) cm long, (3)4.2-6.1(10.1) mm wide; peduncles (10)24-68(130) mm, at least some extending beyond the subtending sheaths at maturity, with 2-13 rames; rames (2)2.4-4(5) cm, usually exserted at maturity, pubescence increasing in density distally within each internode. Sessile spikelets (3)4-4.5(6.9) mm; keels of lower glumes scabrous above (and sometimes below) the midpoint; awns 17-24 mm; anthers 1, 0.7-1.4 mm, yellow. Pedicellate spikelets vestigial or absent. 2n = 20.

Andropogon liebmannii has two varieties. Andropogon liebmannii var. pungensis (Ashe) C.S. Campb., the variety found in the Flora region, differs from A. liebmannii Hack. var. liebmannii, which grows in Mexico, in having culms that are usually more than 80 cm tall, leaves that are more than 15 cm long, and sessile spikelets that are more than 4.2 mm long; in var. pungensis the culms are usually less than 90 cm tall, the leaves less than 15 cm long, and the sessile spikelets less than 4.2 mm long.

Andropogon liebmannii var. pungensis grows along the coastal plain of the southeastern United states in bog, swamp, savannahs, and flatwoods. It used to be treated as a species, which was known as A. mohrii (Vasey) Hack. The English name 'Mohr's Bluestem' reflects this treatment.


9.   Andropogon gyrans Ashe

Plants cespitose, cylindrical to ovate above. Culms 30-100(140) cm; internodes usually glaucous; branches mostly erect, straight. Sheaths smooth; ligules 0.3-1.5 mm, sometimes ciliate, cilia to 0.7 mm; blades 6-48 cm long, 0.8-5 mm wide, glabrous or densely pubescent with spreading hairs. Inflorescence units 2-31 per culm; subtending sheaths (2.6)4.1-4.5(13.5) cm long, (1.5)2.7-4.7(8) mm wide; peduncles (1)5-31(195) mm, with 2-5 rames; rames (1.5)2.8-4.2(6) cm, exserted or not at maturity, pubescence increasing in density distally within each internode. Sessile spikelets (3)3.9-4.7(5.7) mm; callus hairs 1-5 mm; keels of lower glumes scabrous only beyond midlength; awns 8-24 mm; anthers 1, 0.6-1.4(1.7) mm, yellow or purple. Pedicellate spikelets vestigial or absent. 2n = 20.

Andropogon gyrans extends from the southeastern United States to the Caribbean and Central America.

1
Ligules 0.3-1.1 mm long; rames usually hidden within the more or less overlapping and inflated upper sheaths at maturity; plants usually of well-drained soils ..... var. gyrans
Ligules 0.8-1.5 mm long; rames usually exposed at maturity; plants of wet habitats ..... var. stenophyllus


Andropogon gyrans Ashe var. gyrans
Elliott's Beardgrass

Ligules 0.3-0.8(1.1) mm. Inflorescence units usually with 2-5 rames; rames usually concealed at maturity.

Andropogon gyrans var. gyrans generally grows in dry, sandy soil of roadsides, embankments, fields, and pine or oak woods, occasionally in moister soil. Its range extends south from the United States to the Caribbean and Central America. Plants from Florida and Mississippi do not have inflated sheaths.


Andropogon gyrans var. stenophyllus (Hack.) C.S. Campb.

Ligules (0.8)1.1-1.5 mm. Inflorescence units usually with 2 rames; rames usually exposed at maturity.

Andropogon gyrans var. stenophyllus grows in ditches, bogs, savannahs, and pond margins of the coastal plain, from eastern Texas to North Carolina.


10.   Andropogon tracyi Nash
Tracy's Bluestem

Plants cespitose, upper portion dense, cylindrical. Culms 50-120 cm; internodes not glaucous; branches mostly erect, straight. Sheaths smooth; ligules 0.2-0.5 mm, ciliate, cilia 0.2-0.8 mm; blades 10-22 cm long, 1.2-2.6 mm wide, glabrous or sparsely pubescent, with spreading hairs. Inflorescence units 3-11 per culm; subtending sheaths (2.8)4.1-5.8(7.2) cm long, (3)4-4.7(5.8) mm wide; peduncles (9)14-31(65) mm, with 2 rames; rames (1.5)2.4-3.6(4.2) cm, usually exserted at maturity, pubescence increasing in density distally within each internode. Sessile spikelets (4)4.8-5(5.5) mm; callus hairs 1.5-3.5 mm; keels of lower glumes scabrous only above the midpoint; awns 11-23 mm; anthers 1, 1.2-2 mm, yellow. Pedicellate spikelets vestigial or absent. 2n = 20.

Andropogon tracyi grows on sandhills, sandy pinelands, and scrublands of the southeastern United States. It resembles A. longiberbis, but usually differs in having sparsely pubescent blades and a more slender appearance.


11.   Andropogon brachystachyus Chapm.
Shortspike Bluestem

Plants cespitose, open and ovate to obpyramidal above. Culms 1.1-3.1 m; internodes not glaucous; branches arching. Sheaths smooth; ligules 0.2-0.5 mm, ciliate, cilia 0.6-1.5 mm; blades 21-54 cm long, 2.3-6 mm wide, glabrous or sparsely pubescent, with spreading hairs. Inflorescence units 12-190 per culm; subtending sheaths (2.1)2.4-3.5(4.1) cm long, (2.3)2.6-3(3.8) mm wide; peduncles (13)20-31(43) mm, with 2(3) rames; rames (1.2)1.5-2.1(2.6) cm, usually exserted at maturity, pubescence increasing in density distally within each internode. Sessile spikelets (4.1)4.4-4.6(5) mm; callus hairs 1-1.5 mm; keels of lower glumes scabrous only above the midpoint; awns 2-11 mm; anthers 1, 1.4-2.4 mm, red. Pedicellate spikelets vestigial or absent. 2n = 20.

Andropogon brachystachyus grows in sandy, often seasonally wet soils of flatwoods, savannahs, pond margins, and scrublands of the southeastern United States. It sometimes forms large populations, but does not invade disturbed sites as do some morphologically similar forms of A. virginicus var. virginicus.


12.   Andropogon virginicus L.
Broomsedge Bluestem

Plants cespitose, dense and cylindrical to obpyramidal above. Culms 40-210 cm; internodes glaucous or not; branches erect to ascending, usually straight, sometimes arching. Sheaths usually smooth, rarely somewhat scabrous; ligules 0.2-1 mm, ciliate, cilia 0.2-1.3 mm; blades 11-52 cm long, 1.7-6.5 mm wide, smooth and glabrous or sparsely to densely pubescent with spreading hairs. Inflorescence units 6-195 per culm; subtending sheaths (2.1)3.1-4.6(6.7) cm long, (1.7)3-3.8(5.6) mm wide; peduncles usually (1)4-6(30) mm, with 2-7 rames; rames (0.5)1.7-2.8(4.4) cm, sometimes exserted at maturity, pubescence sparse basally and increasing in density distally within each internode. Sessile spikelets (2.6)3.5-3.8(4.7) mm; callus hairs 1-3 mm; keels of lower glume usually smooth below midlength, scabrous distally; awns 6-21 mm; anthers 1(3), 0.6-1.5 mm, yellow or purple. Pedicellate spikelets vestigial to absent. 2n = 20.

Andropogon virginicus is native from the southeastern United States to northern South America, but has become established outside its native range in California, Hawaii, Japan, and Australia. Three varieties are recognized, two of which contain morphologically distinct variants. Andropogon virginicus hybridizes with A. glomeratus and A. longiberbis (Campbell 1986).

1
Leaves bluish-green, more or less strongly glaucous ..... var. glaucus
Leaves green, sometimes somewhat glaucous (2)
2
Sheaths subtending the inflorescence units (1.7)2.4-3.1(4) mm wide; inflorescences units usually with 2 rames; rames (1.3)1.5-2.3(3) cm long; peduncles (1) 4-9 (30) mm long ..... var. decipiens
Sheaths subtending the inflorescences units (2.2)3.3-4.4(5.6) mm wide; inflorescence units with 2-5(7) rames; rames (0.5)1.9-3.3(4.4) cm long; peduncles (2)3-6(12) mm long ..... var. virginicus


Andropogon virginicus var. decipiens C.S. Campb.

Culms 70-170 cm. Leaves green, sometimes slightly glaucous. Inflorescence units usually with 2 rames; subtending sheaths (1.7)2.4-3.1(4) mm wide; peduncles (1) 4-9 (30) mm; rames (1.3)1.5-2.3(3) cm.

Andropogon virginicus var. decipiens grows in flatwoods, scrublands, and disturbed sites, such as roadsides and cleared timberlands, of the southeastern coastal plain.


Andropogon virginicus var. glaucus Hack.

Culms 60-180 cm. Leaves bluish-green, more or less strongly glaucous. Inflorescence units with 2(3) rames; subtending sheaths (2.7)3.1-3.8(5.5) mm wide; peduncles (2)3-4(10) mm; rames (1.4)1.7-3(4) cm, not exserted.

Andropogon virginicus var. glaucus grows on moist or dry soils of the coastal plain, from southern New Jersey to eastern Texas. Plants growing on sandy, well-drained soils differ from those on poorly drained slopes in being glabrous (rather than pubescent) beneath the subtending sheaths of the inflorescence units, and in tending to have shorter rames.


Andropogon virginicus L. var. virginicus

Culms 40-210 cm; internodes green. Leaves green or slightly glaucous, glabrous or pubescent, at least on the margins near the collar. Inflorescence units with 2-5(7) rames; subtending sheaths (2.2)3.3-4.4(5.6) mm wide; peduncles (2)3-6(12) mm; rames (0.5)1.9-3.3(4.4) cm, not exserted.

Andropogon virginicus var. virginicus is the widespread and weedy variety of A. virginicus that grows as a native species from the central plains through Mexico and Central America to Colombia and, as a naturalized species, in California, Hawaii, Japan, and Australia. Plants colonizing openings in mature vegetation created by disturbance have green culms and green, pubescent leaves. Those growing in poorly drained soils of pond margins, swales, and cutover flatwoods have glaucous culms and glabrous, green to somewhat glaucous leaves. Glaucous plants of A. virginicus var. virginicus differ from those of var. decipiens in having no exposed rames and, often, wider sheaths subtending the inflorescence units.


13.   Andropogon longiberbis Hack.
Hairy Bluestem

Plants cespitose; cylindrical to oblong and more or less open in the upper portion. Culms 50-100(150) cm; internodes green, sometimes somewhat glaucous just below the node; branches mostly erect, straight. Sheaths not scabrous; ligules 0.2-0.6 mm, ciliate, cilia 0.3-0.6 mm; blades 11-50 cm long, 2-5.5 mm wide, sparsely to densely pubescent, most hairs appressed. Inflorescence units 7-97 (usually about 45) per culm; subtending sheaths (2.5)3-4.5(6) cm long, (2.5)3.2-4.1(5.5) mm wide; peduncles (1)3-4(13) mm, with 2(3) rames; rames (1.3)1.8-2.6(4) cm, not exserted at maturity, pubescence increasing in density distally within each internode. Sessile spikelets (3.5)4.1-4.5(5) mm; callus hairs 1.5-5 mm; keels of lower glumes scabrous only above the midpoint; awns 10-21 mm; anthers 1, 0.9-1.6 mm, yellow. Pedicellate spikelets vestigial or absent. 2n = 20.

Andropogon longiberbis grows in sandy or rocky soils of roadsides, dunes, sandhills, pinelands, and fields, from the southeastern United States to the Bahamas. It resembles A. tracyi, but usually differs in having more densely pubescent blades and a less slender appearance.

Andropogon longiberbis appears to hybridize with both A. virginicus var. virginicus and A. glomeratus var. pumilus.


14.   Andropogon glomeratus (Walter) Britton, Sterns & Poggenb.
Bushy Bluestem, Bushy Beardgrass

Plants cespitose, upper portion dense, oblong to oblanceolate or obpyramidal. Culms 20-250 cm; internodes green, sometimes glaucous; branches mostly erect, straight. Sheaths usually scabrous, sometimes smooth; ligules 0.6-2.2 mm, sometimes ciliate, cilia to 0.9 mm; blades 13-109 cm long, 2.9-9.5 mm wide, glabrous or sparsely to densely pubescent, hairs usually spreading, rarely appressed. Inflorescence units 10-600 per culm; subtending sheaths (2.0)2.9-4.4(6.5) cm long, (1.5)2.3-3.4(4.4) mm wide; peduncles (1)6-14(60) mm, with 2(4) rames; rames (1)1.7-2.5(3.5) cm, exserted or not at maturity, pubescence sparse basally and increasing in density distally within each internode. Sessile spikelets 3-5 mm; callus hairs 1-2.5 mm; keels of lower glumes sometimes scabrous below midlength, usually scabrous distally; awns 6-19 mm; anthers 1(3), 0.5-1.5 mm, yellow, red, or purple. Pedicellate spikelets vestigial or absent, sterile. 2n = 20.

Andropogon glomeratus hybridizes with both A. longiberbis and A. virginicus. Some of its varieties are morphologically similar to the latter species.

1
Blades glaucous, glabrous, and smooth ..... var. glaucopsis
Blades green, often pubescent or scabrous (2)
2
Sheaths subtending the inflorescence units 1.5-3 mm wide; leaf sheaths usually smooth; ligules ciliate, the cilia 0.2-0.9 mm long ..... var. pumilus
Sheaths subtending the inflorescence units (1.5)2.3-3.4(4.4) mm wide; leaf sheaths often scabrous; ligules, when ciliate, with the cilia no more than 0.5 mm long (3)
3
Keels of the lower glumes scabrous below and beyond midlength ..... var. scabriglumis
Keels of the lower glumes usually smooth below midlength, scabrous distally (4)
4
Upper portion of the plants oblong to obpyramidal; mature peduncles (4)11-35(60) mm long; anthers eventually falling ..... var. glomeratus
Upper portion of the plants cylindrical to oblong; mature peduncles 2-5(8) mm long; withered remnants of anthers retained within the spikelets ..... var. hirsutior


Andropogon glomeratus var. glaucopsis (Elliott) C. Mohr

Plants usually oblong in the upper portion, sometimes cylindrical. Culms 1.2-2.2 m; internodes glaucous. Sheaths (1.3)2.3-3.1(4.7) mm wide, usually smooth; ligules ciliate or not, cilia to 0.2 mm; blades glaucous, glabrous, smooth. Subtending sheaths of inflorescence units usually 2-2.5 mm wide; peduncles shorter than 10 mm; rames usually shorter than 2 cm, not exserted at maturity. Keels of lower glumes usually scabrous beyond midlength.

Andropogon glomeratus var. glaucopsis grows in flatwoods, bogs, ditches, swamps, pond margins, and swales of the southeastern coastal plain.


Andropogon glomeratus (Walter) Britton, Sterns & Poggenb. var. glomeratus

Plants oblong to pyramidal in the upper portion. Culms 60-160 cm; internodes not glaucous. Sheaths (2)2.5-3.4(4.7) mm wide, scabrous; ligules sometimes ciliate, cilia to 0.3 mm; blades green, usually scabrous. Subtending sheaths of inflorescence units usually 2.5-3.4 mm wide; peduncles (4)11-35(60) mm; rames usually 2.1-2.9 cm, exserted. Keels of lower glumes usually smooth below midlength, scabrous distally; anthers eventually deciduous.

Andropogon glomeratus var. glomeratus grows in bogs, swamps, savannahs, flatwoods, and ditches of the southeastern United States.


Andropogon glomeratus var. hirsutior (Hack.) C. Mohr

Plants usually oblong in the upper portion, sometimes cylindrical. Culms 1-2 m; internodes not glaucous. Sheaths scabrous; ligules ciliate or not, cilia to 0.3 mm; blades green, usually pubescent. Subtending sheaths of inflorescence units (2)2.4-3.1(4) mm wide; peduncles 2-5(8) mm; rames usually 1.7-2.8 cm, not exserted at maturity. Keels of lower glumes usually smooth below midlength, scabrous distally; anthers often retained within the spikelets.

Andropogon glomeratus var. hirsutior grows in ditches, swales, bogs, flatwoods, and savannahs of the southeastern coastal plain, often forming very large populations in cleared, low ground.


Andropogon glomeratus var. pumilus (Vasey) L.H. Dewey

Plants oblanceolate to obpyramidal in the upper portion. Culms to 2.5 m, but as short as 20 cm in poor soils; internodes not glaucous. Leaf sheaths usually smooth; ligules ciliate, cilia 0.2-0.9 mm; blades green, smooth or pubescent. Subtending sheaths of inflorescence units (2)2.9-4.3(5.2) cm long, 1.5-3 mm wide; peduncles (2)8-15(40) mm; rames 1.3-3 cm, exserted. Keels of lower glumes usually smooth below midlength, scabrous distally; anthers often retained within the spikelets.

Andropogon glomeratus var. pumilus is weedy and grows in disturbed, wet or moist sites. It is abundant and widespread, extending from the southern United States through Central America to northern South America.


Andropogon glomeratus var. scabriglumis C.S. Campb.

Plants oblanceolate to obpyramidal in the upper portion. Culms 80-150 cm; internodes not glaucous. Sheaths usually scabrous; ligules ciliate, cilia 0.2-0.5 mm; blades green, smooth or pubescent. Subtending sheaths of inflorescence units (2.3)2.9-4.5(6.3) cm long, (1.5)2.3-3.3(4.4) mm wide; peduncles (2)5-10(16) mm; rames (1.7)1.9-2.3(2.8) cm, exserted. Keels of lower glumes usually scabrous below and above the midpoint.

Andropogon glomeratus var. scabriglumis grows in moist soils of seepage slopes and the edges of springs, from California to New Mexico and southward into Mexico.