26.17   SCHIZACHYRIUM Nees
J.K. Wipff

Plants annual or perennial; cespitose or rhizomatous, sometimes both cespitose and shortly rhizomatous. Culms 7-210 cm, branched above the bases, often purplish near the nodes. Leaves not aromatic, sheaths open; auricles usually absent; ligules membranous; blades flat, folded, or involute, those of the uppermost leaves often greatly reduced. Inflorescences axillary and terminal, of 1, rarely 2, rames, peduncles subtended by a modified leaf; rames not reflexed, with spikelets in heterogamous sessile-pedicellate spikelet pairs, internodes more or less flattened, filiform to clavate, without a median groove, apices cupulate or fimbriate; disarticulation in the rame axes, below the sessile spikelets. Spikelets somewhat dorsiventrally compressed. Sessile spikelets with 2 florets; glumes exceeding the florets, lanceolate to linear, membranous; lower glumes enclosing the upper glumes, convex, weakly 2-keeled, with several (sometimes inconspicuous) intercostal veins; lower florets reduced to hyaline lemmas; upper florets bisexual, lemmas hyaline, bilobed or bifid to 7/8 of their length (rarely entire), awned from the sinuses; anthers 3. Pedicels free of the rame axes, usually pubescent. Pedicellate spikelets usually shorter than to as long as the sessile spikelets, occasionally longer, sterile or staminate, with 1 floret, often disarticulating as the rame matures; lemmas present in staminate spikelets, hyaline, unawned or with a straight awn of less than 10 mm. x = 10. Name from the Greek schizo, split, and achyron, chaff, referring to the divided lemma.

Schizachyrium is a genus of approximately 60 species that are native to tropical and subtropical regions of the world; nine are native to the Flora region. In North America, the best known species is S. scoparium, which was one of the major constituents of the grasslands that used to cover the central plains. Hitchcock (1951) included both Schizachyrium and Bothriochloa in Andropogon. Most species of Schizachyrium differ from species of the other two genera in having only one rame per peduncle, but S. spadiceum has two. More reliable, but less conspicuous distinguishing features of Schizachyrium are the cupulate tips of the rame internodes, the convex lower glumes, and the presence of veins between the keels of the lower glumes. A few species of Andropogon have solitary rames, but they do not have these other features.


SELECTED REFERENCES Bruner, J.L.1987. Systematics of the Schizachyrium scoparium (Poaceae) complex in North America. Ph.D. dissertation, Ohio State University, Columbus, Ohio, U.S.A. 167 pp.; Gandhi, K.N. 1989. A biosystematic study of the Schizachyrium scoparium complex. Ph.D. dissertation, Texas A&M University, College Station, Texas, U.S.A. 188 pp.; Grelen, H.E. 1974. Pinehills bluestem, Andropogon scoparius Anderss. ex Hack., an anomaly of the A. scoparius complex. Amer. Midl. Naturalist 91:438-444; Hatch, S.L. 1975. A biosystematic study of the Schizachyrium cirratum-Schizachyrium sanguineum complex (Poaceae). Ph.D. dissertation, Texas A&M University, College Station, Texas, U.S.A. 112 pp.; Hitchcock, A.S.1951 [title page 1950]. Manual of the Grasses of the United States, ed. 2, rev. A. Chase. U.S.D.A. Miscellaneous Publication No. 200. U.S. Government Printing Office, Washington, D.C., U.S.A. 1051 pp.; Wipff, J.K. 1996. Nomenclatural combinations in Schizachyrium (Poaceae: Andropogoneae). Phytologia 80:35-39.

1
Peduncles with 2 rames .....1.S. spadiceum
Peduncles with only 1 rame (2)
2
Leaf blades 0.5-2 mm wide, with a longitudinal stripe of white, spongy tissue (formed of bulliform cells) on their adaxial surfaces; plants cespitose; pedicellate spikelets about as long as the sessile spikelets ..... 6. S. tenerum
Leaf blades (1)1.5-9 mm wide, without a longitudinal stripe of white, spongy tissue on their adaxial surfaces; plants cespitose or rhizomatous; pedicellate spikelets equal to or smaller than the sessile spikelets (3)
3
Plants rooting and branching at the lower nodes and at aerial nodes in contact with the soil; leaf collars usually elongate and narrow; plants of sandy coastal habitats (4)
Plants not rooting or branching at the lower nodes; leaf collars neither elongate nor particularly narrow; plants of varied habitats (5)
4
Ligules 0.5-1 mm long, pedicellate spikelets 4.5-8.5 mm long ..... 4. S. maritimum
Ligules 1.5-2 mm long, pedicellate spikelets 1.5-5 mm long ..... 5. S. littorale
5
Pedicel bases 0.2-0.5 mm wide, gradually widening to 0.3-1 mm distally, straight, often somewhat stiff, not tending to curve outward; rames appearing linear (6)
Pedicel bases 0.1-0.2 mm wide, flaring above midlength to about 0.5 mm wide, tending to curve outward; rames appearing somewhat open (8)
6
Pedicellate spikelets 6-8 mm long, about as long as the sessile spikelets, usually staminate, sometimes sterile, unawned ..... 9. S. cirratum
Pedicellate spikelets 0.7-10 mm long, usually shorter than the sessile spikelets, sterile, unawned or awned, the awns up to 6 mm long (7)
7
Upper lemmas cleft for 2/3-7/8 of their length; lower glumes glabrous or pubescent .... 8. S. sanguineum
Upper lemmas cleft for up to 1/2 of their length; lower glumes glabrous ..... 2. S. scoparium
8
Upper lemmas indurate at the base, cleft 3/4-7/8 of their length; leaf blades 2.5-10 cm long; pedicellate spikelets 0.5-2 mm long; plants cespitose; known only from peninsular Florida ..... 7. S. niveum
Upper lemmas membranous at the base, cleft for up to 1/2 of their length; leaf blades 7-105 cm long; pedicellate spikelets 0.7-10 mm long; plants cespitose or not; widespread, including Florida (9)
9
Plants cespitose, not or shortly rhizomatous ..... 2. S. scoparium
Plants not cespitose, strongly rhizomatous (10)
10
Pedicellate spikelets awned, awns to 4 mm; leaf blades usually 3.5-9 mm wide; culms usually 1-3 mm thick; plants of sandy soils ..... 2. S. scoparium
Pedicellate spikelets unawned or the awns less than 1 mm; leaf blades 1-3 mm wide; culms usually less than 1 mm thick; plants of oölitic soil ..... 3. S. rhizomatum


1.   Schizachyrium spadiceum (Swallen) Wipff
Honey Bluestem

Plants cespitose. Culms 60-95 cm, slender, erect, glabrous. Leaves glaucous; sheaths compressed, scabridulous, glabrous or almost so; ligules 1-1.5 mm, truncate, erose-ciliate; blades 10-25 cm long, 2-2.5 mm wide, flat, scabrous, young blades ciliate basally. Peduncles 5-9 cm, mostly erect, often included in the subtending leaves, with 2 rames; rames 3.5-5 cm, enclosed or exerted at maturity; internodes 4-6.3 mm, ciliate proximally, densely villous on the distal 1/2-2/3, hairs 4-7 mm. Sessile spikelets 7-8 mm; calluses 0.2-0.5 mm, hairs 1-2 mm; lower glumes glabrous, keels scabridulous distally; awns 14.5-17.5 mm, once-geniculate. Pedicels 5-6 mm, hairs 5-7 mm. Pedicellate spikelets 0.8-4 mm, sterile, unawned. 2n = unknown.

Schizachyrium spadiceum was once thought to be a Mexican endemic, but it is now known from limestone slopes in Brewster County, Texas.


2.   Schizachyrium scoparium (Michx.) Nash

Plants cespitose or rhizomatous, green to purplish, sometimes glaucous. Culms 7-210 cm tall, usually 1-3 mm thick, not rooting or branching at the lower nodes. Sheaths rounded or keeled, glabrous or pubescent, sometimes glaucous; ligules 0.5-2 mm, collars neither elongate nor narrowed; blades 7-105 cm long, 1.5-9 mm wide, without a longitudinal stripe of white, spongy tissue. Peduncles 0.8-10 cm; rames 2.5-8 cm, partially to completely exserted, usually somewhat open; internodes 3-7 mm, usually arcuate at maturity, ciliate on at least the distal 1/2 (sometimes throughout), hairs 1.5-6 mm. Sessile spikelets 3-11 mm; calluses 0.5-1(2) mm, hairs 0.3-4 mm; lower glumes glabrous; upper lemmas membranous throughout, cleft to 1/2 their length; awns 2.5-17 mm. Pedicels 3-7.5 mm long, 0.1-0.2 mm wide at the base, flaring above midlength to 0.3-0.5 mm, straight or curving outwards. Pedicellate spikelets 0.7-10 mm, sometimes shorter than the sessile spikelets, sterile or staminate, unawned or awned, awns to 4 mm, when sterile, the lemma usually absent. 2n = 40.

Schizachyrium scoparium is a widespread grassland species, extending from Canada to central Mexico. It is one of the principal grasses in the tallgrass prairies that used to dominate the central plains of North America. It exhibits considerable variation, much of it clinal. The following varieties are recognized because they are morphologically, ecologically, and geographically distinctive.

1
Plants not cespitose, strongly rhizomatous; pedicellate spikelets sterile ..... var. stoloniferum
Plants usually cespitose, not or shortly rhizomatous; pedicellate spikelets staminate or sterile (2)
2
Pedicellate spikelets of the proximal spikelet units on each rame staminate, 5-10 mm long, with a lemma, pedicellate spikelets of the distal units usually smaller (1-4 mm) and sterile; sheaths and blades densely tomentose to glabrate ..... var. divergens
Most pedicellate spikelets sterile, 1-6 mm long, without a lemma; sheaths and blades usually glabrous, occasionally pubescent ..... var. scoparium


Schizachyrium scoparium var. divergens (Hack.) Gould
Pinehill Bluestem

Plants cespitose. Culms 7-180 cm. Sheaths densely tomentose initially, sometimes glabrate, margins usually pilose distally; blades 12-30 cm long, 3.5-5 mm wide; initially densely tomentose, becoming glabrous. Rames 3-5 cm, with 7-12 spikelets, usually partially to wholly exserted, sometimes appearing linear; internodes 3.5-6 mm, often sparsely pubescent, hairs 1.5-3 mm. Sessile spikelets 6-10 mm; calluses about 0.3 mm, hairs to 2 mm; awns 9-15 mm. Pedicels 3.5-6.5 mm, curving out at maturity. Pedicellate spikelets on the proximal portion of the rames 5-10 mm, mostly staminate, with lemmas, distal spikelets often smaller (1-4 mm) and sterile, unawned or awned, awns to 2 mm.

Schizachyrium scoparium var. divergens is common in the south central pinelands of the United States. The pubescence of the leaves varies across its range, western plants having longer and more villous leaves than those in the east and, towards Mississippi, the pubescence is confined to the sheaths. Schizachyrium scoparium var. divergens intergrades with var. scoparium.

Grelen (1974) found that plants of S. scoparium var. divergens from western Louisiana, Oklahoma, and Arkansas produced mostly staminate pedicellate spikelets, plants from southeastern Louisiana and southeastern Mississippi produced mostly sterile pedicellate spikelets, and plants from western Mississippi varied in this character.


Schizachyrium scoparium (Michx.) Nash var. scoparium
Little Bluestem, Broom Beardgrass, Broom Bluestem, Schizachyrium à Balais

Plants usually cespitose, sometimes producing short rhizomes. Culms 30-210 cm. Sheaths usually glabrous, keeled; blades 9-45 cm long, 1.5-9 mm wide, flat, usually glabrous, occasionally pubescent. Peduncles to 10 cm; rames 2-8 cm, with 6-13 spikelets, exserted. Sessile spikelets 6-11 mm; calluses about 0.5 mm, hairs to 2.5 mm, awns 2.5-17 mm; Pedicels 3-7.5 mm, straight or curving out at maturity. Pedicellate spikelets usually 1-6 mm, sterile, without lemmas, occasionally staminate and with a lemma, unawned or awned, awns to 4 mm.

Schizachyrium scoparium var. scoparium grows in a variety of soils and in open habitats. It was once a dominant component of the prairie grasslands that extended through the central plains of North America and into Mexico, but it has largely been replaced by fields of maize, wheat, sorghum, sunflowers, and field mustard. It is the most variable of the varieties recognized within S. scoparium, with morphological features that vary independently and continuously across its range, coming together in distinctive combinations in some regions. Some of these phases have been named as varieties, or even species, but they have proven to be untenable taxonomic entities when plants from throughout the range of the species are considered.


Schizachyrium scoparium var. stoloniferum (Nash) Wipff
Creeping Bluestem

Plants not cespitose, with long, scaly rhizomes. Culms 58-210 cm. Sheaths usually pubescent near the collars; blades 10-39 cm long, 3.5-9 mm wide, pubescent near the collars. Rames 2-6.5 cm, with 6-14 spikelets, usually partially to fully exserted; internodes pubescent, hairs to 4.5 mm. Sessile spikelets 5-10 mm; calluses with hairs to 2.5 mm; awns 6-14 mm. Pedicels 3.5-5 mm, curving out at maturity. Pedicellate spikelets 0.75-4 mm, sterile, awned, awns 1-3 mm.

Schizachyrium scoparium var. stoloniferum grows in sandy soils of woodland openings and roadsides from southern Alabama and Georgia south to the Everglades. Northern populations consist of widely spaced, weak culms growing in rather bare sand; southern populations consist of dense, vigorous stands with taller, more robust culms growing primarily along roadsides, possibly spread by grading equipment. Some clones, particularly in the south, are largely sterile.


3.   Schizachyrium rhizomatum (Swallen) Gould
Florida Little Bluestem

Plants with short, scaly rhizomes. Culms 50-90 cm tall, usually less than 1 mm thick, not rooting or branching at the lower nodes, usually glabrous. Ligules about 0.5 mm; blades 9.5-25 cm long, 1-3 mm wide, usually folded, without a longitudinal stripe of white, spongy tissue. Peduncles 3-7 cm; rames 2-5.5 cm, with 5-14 spikelets, partially to fully exserted, collars neither elongate nor particularly narrow. Sessile spikelets 4-7.5 mm; calluses sparsely pubescent, hairs to 1.5 mm; awns 2.5-10 mm; upper lemmas membranous throughout, apices cleft for about 1/4 of their length. Pedicels 3.5-5 mm, ciliate, hairs to 2.3 mm, pedicel bases 0.1-0.2 mm wide, flaring above midlength to about 0.5 mm wide, tending to curve outward, rames appearing somewhat open. Pedicellate spikelets 2.5-5.5 mm, unawned or with awns to 1 mm.

Schizachyrium rhizomatum grows in open glades and on the margins of pine woodlands, and is endemic to Florida. It is restricted to thin, oölitic soils that are often saturated with water and is a common species in marl prairies of Monroe and Dade Counties, Florida. On the Florida Keys, it forms sparse stands, occasionally mixed with Andropogon gracilis. Modifed May 30, 2009 on basis of literature review by Ann Johnson for the Florida Natural Are Inventory.


4.   Schizachyrium maritimum (Chapm.) Nash
Gulf Bluestem

Plants often appearing rhizomatous. Culms 35-80 cm, solitary, decumbent, branching at the lower nodes, often rooting from nodes in contact with the soil. Leaves glaucous throughout; sheaths shorter than the internodes, keeled; collars constricted, elongate; ligules 0.5-1 mm; blades 11-142 cm long, 3.5-5.5 mm wide, folded, without a longitudinal stripe of white, spongy tissue. Peduncles 1-6 cm; subtending leaf sheaths 3.2-6.6 cm long, 3-6.5 mm wide; rames 2.5-6.5 cm, flexuous, usually partially exserted, appearing somewhat open; internodes 4-5.5 mm, straight, pubescent for 1/2-3/4 of their length, hairs 2.5-6 mm. Sessile spikelets 9-11 mm; calluses 0.3-0.5 mm; hairs to 1 mm; awns 8-13 mm. Pedicels 5-7 mm, as conspicuously villous as the rachis. Pedicellate spikelets 4.5-8.5 mm, staminate, unawned or awned, awns to 3.5 mm. 2n = 40.

Schizachyrium maritimum is endemic to the southeastern United States, growing in sandy areas, usually at the ocean waterline but also along roads in low, dune areas, from Louisiana to the Florida panhandle.

The plants often appear rhizomatous because the lower, decumbent portions of the culms are frequently covered by sand. It is an effective sand binder and can withstand frequent inundation by sea water, the constricted collar permitting the blades to sway freely when subjected to wind or wave action.


5.   Schizachyrium littorale (Nash) E.P. Bicknell
Shore Bluestem, Dune Bluestem

Plants cespitose, sometimes appearing rhizomatous, glaucous. Culms 39-160 cm, branching at the lower nodes, often rooting from nodes in contact with the soil; lower internodes usually shortened and compressed. Leaves glaucous; collars usually constricted, elongate; auricles flexible, yellow; ligules 1.5-2 mm; blades 10-30 cm long, 3.5-6.5 mm wide, without a longitudinal stripe of white, spongy tissue. Peduncles 0.5-5 mm; rames 3-9 cm, with 13-19 spikelets, arcuate at maturity; internodes 4-6 mm, densely villous, hairs 3-7.5 mm. Sessile spikelets 6-10 mm; calluses 0.2-0.5 mm, glabrous; lower glumes glabrous; awns 9-20 mm. Pedicels 5-7 mm, hairy distally, hairs 5-7 mm. Pedicellate spikelets 1.5-5 mm, often staminate, unawned or awned, awns to 3.5 mm. 2n = 40.

Schizachyrium littorale is restricted to shifting, coastal sand dunes of the Gulf, Atlantic, and Great Lakes coasts of the United States. It often appears rhizomatous because the lower nodes are frequently covered by sand.


6.   Schizachyrium tenerum Nees
Slender Bluestem

Plants cespitose. Culms 60-100 cm, sometimes reclining or decumbent, glabrous. Collars not elongate, about as wide as the blade; ligules to 0.5 mm, ciliolate; blades 5-15 cm long, 0.5-2 mm wide, involute or flat, glabrous or sparsely hairy basally, with a wide central zone of bulliform cells evident on the adaxial surfaces as a longitudinal stripe of white, spongy tissue. Rames 2-6 cm, eventually long-exserted; internodes 2-4 mm, straight, glabrous. Sessile spikelets 3.5-4.5 mm; calluses 0.5-1 mm, hairs to 1.2 mm; lower glumes glabrous; upper lemmas acute, entire; awns 6-10 mm. Pedicels 3-5 mm, glabrous. Pedicellate spikelets usually as long as or slightly longer than the sessile spikelets, sterile, unawned. 2n = 60.

Schizachyrium tenerum is an uncommon species in the southeastern United States, where it grows on sandy soils in pine forest openings and coastal prairies. Its range extends hrough Central America into South America.


7.   Schizachyrium niveum (Swallen) Gould
Pinescrub Bluestem

Plants cespitose. Culms 49-90 cm, not rooting or branching at the lower nodes. Leaves usually completely glabrous; sheaths keeled; ligules 0.5-1 mm; blades 2.5-10 cm long, (1)2-4 mm wide, flat, without a longitudinal stripe of white, spongy tissue. Peduncles 2-4.6 cm; subtending leaf sheaths 2.5-4 cm long, 1.5-3.5 mm wide; rames 2.5-4.5 cm, somewhat open and usually partially exserted, varying from included to completely exserted; internodes 3-7 mm, straight, densely villous for their full length, hairs 0.5-2.5 mm, silvery-white. Sessile spikelets 5-6.5 mm; calluses with 0.5-1 mm hairs; lemmas slightly indurate at the base (unique among the species treated here in this respect), cleft for 3/4-7/8 of their length; awns 10.5-15 mm. Pedicels 5-6.5 mm long, 0.1-0.2 mm wide at the base, flaring beyond midlength to about 0.5 mm, densely villous. Pedicellate spikelets 0.5-2 mm, sterile, unawned or awned, awns 1-2 mm. 2n = 40.

Schizachyrium niveum is an endangered, rare species known only from central peninsular Florida, where it occurs in openings and sandhills of Ceratiola-pine-oak woodlands. It has been reported from south central Georgia, but Bruner (1987) found no evidence for the report. Of the two recent collections in Florida, he relocated one, in an area favored by real estate developers.


8.   Schizachyrium sanguineum (Retz.) Alston

Plants cespitose. Culms 40-120 cm, erect, not rooting or branching at the lower nodes, glabrous. Sheaths glabrous, rounded; ligules 0.7-2 mm; blades 7-20 cm long, 1-6 mm wide, usually with long, papillose-based hairs basally, glabrous elsewhere, sometimes scabrous, without a longitudinal stripe of white, spongy tissue. Peduncles 4-6 cm; rames 4-15 cm, not open, usually almost fully exserted at maturity; internodes 4-6 mm, straight, from mostly glabrous with a tuft of hairs at the base to densely hirsute all over. Sessile spikelets 5-9 mm; calluses 0.5-1 mm, hairs to 2 mm; lower glumes glabrous or densely pubescent; upper lemmas cleft for (2/3)3/4-7/8 of their length; awns 15-25 mm. Pedicels 3-6 mm long, 0.3-0.5 mm wide at the base, gradually widening to about 0.6-0.8 mm at the top, straight. Pedicellate spikelets 3-5 mm, usually evidently shorter than the sessile spikelets, sterile or staminate, awned, awns 0.3-6 mm.

Schizachyrium sanguineum extends from the southern United States to Chile, Paraguay, and Uruguay.

1
Lower glumes of the sessile spikelets glabrous or scabrous; pedicels ciliate on 1 edge ..... var. sanguineum
Lower glumes of the sessile spikelets pubescent to hirsute; pedicels ciliate on both edges ..... var. hirtiflorum


Schizachyrium sanguineum var. hirtiflorum (Nees) S.L. Hatch
Hairy Crimson Bluestem

Culms 40-120 cm, branching at the upper nodes, glaucous. Ligules 1-2 mm; blades 10-20 cm long, 1.5-5 mm wide. Rames 4-10(12) cm; internodes scabrous, glabrous or hirsute. Sessile spikelets 5-9 mm; lower glumes sparsely to densely hirsute on the back; awns 15-25 mm. Pedicels arcuate at maturity, ciliate on both edges distally. Pedicellate spikelets 3-5 mm, staminate or sterile, awns 0.3-5 mm. 2n = 40, 60, 70, 100.

In the Flora region, Schizachyrium sanguineum var. hirtiflorum grows on rocky slopes and well-drained soils from Arizona to southwestern Texas and Florida, and is considered a good forage species. Its range extends through Central America to Chile, Paraguay, and Uruguay.


Schizachyrium sanguineum (Retz.) Alston var. sanguineum
Crimson Bluestem

Culms 60-120 cm. Ligules 0.7-1.5 mm; blades usually 1-6 mm wide. Rames 5-8 cm; internodes 4-6 mm, glabrous except for a tuft of hairs at the base. Sessile spikelets: glumes glabrous or scabrous; awns 15-25 mm. Pedicels straight, ciliate on 1 edge distally. Pedicellate spikelets about 3 mm, sterile, awns 3-6 mm. 2n = 40, 50, 60, 70, 80.

Schizachyrium sanguineum var. sanguineum grows in tropical and subtropical regions of America, Africa, and Asia. Within the Flora region, it is known only from the pine woods of Alabama and Florida.


9.   Schizachyrium cirratum (Hack.) Wooton & Standl.
Texas Schizachyrium, Texas Beardgrass

Plants cespitose or shortly rhizomatous. Culms 31-75 cm, often decumbent, not rooting or branching at the lower nodes, glabrous, glaucous, sometimes purplish. Ligules 1-2.5 mm; blades 6-17 cm long, 2-4 mm wide, glabrous, without a longitudinal stripe of white, spongy tissue. Rames 4-6 cm, usually exerted, straight, often somewhat stiff, not flexuous, appearing linear; internodes straight, with a tuft of hairs near the base, elsewhere glabrous or ciliate on the margins. Sessile spikelets 8-10 mm; calluses 0.3-0.6 mm, hairs 0.5-1.2 mm; glumes glabrous or scabrous; awns 13-24 mm. Pedicels 3.5-5 mm long, 0.2-0.5 mm wide at the base, widening to 0.5-1 mm, straight, with a tuft of hairs at the base, distal 1/2 usually ciliate on 1 side, sometimes on both sides. Pedicellate spikelets 6-8 mm, about as long as the sessile spikelets, usually staminate, sometimes sterile, unawned. 2n = 20 (for var. cirratum).

Schizachyrium cirratum grows on rocky slopes, mostly at elevations of 5000 feet or higher, from southern California to western Texas into Mexico, and is known from South America. It is an excellent forage grass. Plants in the Flora region differ from those in central Mexico in being essentially non-rhizomatous and in having glabrous rame axes and pedicels that are ciliate only on the distal half.