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slender bluestem, slender little bluestem

bluestem, little bluestem

Habit Plants cespitose. Plants annual or perennial; cespitose or rhizomatous, sometimes both cespitose and shortly rhizomatous.
Culms

60-100 cm, sometimes reclining or decumbent, glabrous.

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.

Pedicels

3-5 mm, glabrous.

free of the rame axes, usually pubescent.

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.

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.

Pedicellate

spikelets usually as long as or slightly longer than the sessile spikelets, sterile, unawned.

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.

2n

= 60.

Schizachyrium tenerum

Schizachyrium

Distribution
from FNA
AL; FL; GA; LA; MS; OK; TX; PR
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NY; OH; OK; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; HI; PR; AB; BC; MB; NB; NS; ON; QC; SK; Virgin Islands
[BONAP county map]
Discussion

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 through Central America into South America.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Peduncles with 2 rames
S. spadiceum
1. 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
S. tenerum
2. 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
4. Ligules 0.5-1 mm long, pedicellate spikelets 4.5-8.5 mm long
S. maritimum
4. Ligules 1.5-2 mm long, pedicellate spikelets 1.5-5 mm long
S. littorale
3. Plants not rooting or branching at the lower nodes; leaf collars neither elongate nor particularly narrow; plants of varied habitats.
→ 5
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
6. Pedicellate spikelets 6-8 mm long, about as long as the sessile spikelets, usually staminate, sometimes sterile, unawned
S. cirratum
6. 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
S. sanguineum
7. Upper lemmas cleft for up to 1/2 of their length; lower glumes glabrous
S. scoparium
5. 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
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
S. niveum
8. 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
S. scoparium
9. 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
S. scoparium
10. 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 oolitic soil
S. rhizomatum
Source FNA vol. 25, p. 672. FNA vol. 25, p. 666.
Parent taxa Poaceae > subfam. Panicoideae > tribe Andropogoneae > Schizachyrium Poaceae > subfam. Panicoideae > tribe Andropogoneae
Sibling taxa
S. cirratum, S. littorale, S. maritimum, S. niveum, S. rhizomatum, S. sanguineum, S. scoparium, S. spadiceum
Subordinate taxa
S. cirratum, S. littorale, S. maritimum, S. niveum, S. rhizomatum, S. sanguineum, S. scoparium, S. spadiceum, S. tenerum
Synonyms Andropogon tener
Name authority Nees Nees
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