Species Key

Note:  If you do not know to which genus your grass belongs, start with the .  The information contained under "Species Key" is a collection of the keys found on individual genera pages.  This comprehensive species key page is intended to be a supplementary resource which can be printed and serve as a field reference.

Andropogon, Bothriochloa, Schizachyrium

Schizachyrium is similar but differs by having the ultimate inflorescence axes (racemes or rames of some authors) single rather then paired.  Also similar, Bothriochloa pertusa has a conspicuous pit on each spikelet.

1. Spikelets with a conspicuous gland or pit (visible with a hand lens) on the lower glume… (Spikelets 3-4 mm long; awn 10-17 mm long)

1. Spikelets glandless…2

2. Ultimate branches of the inflorescense (rames) single, zig-zag…9

2. Rames paired...3

3. Peduncles exposed, curved or drooping; ultimate inflorescence branches (rames) < 2.1 cm long…...

3. Peduncles hidden, or exposed and straight; rames of variable lengths, usually (but not always) exceeding 2.1 cm long...4

4. Sessile spikelets usually (4.5)5-8.4 mm long.  Pedicellate spikelets well developed … (plants usually in dry pine woods, with few [easily counted] inflorescence units [vs crowded and numerous in A. floridanus],  rames 3-6 cm, on  long exposed straight peduncles; anthers 3; awns to 25 mm)

4. Sessile spikelets usually < 4.5 mm long.  Pedicellate spikelets absent or vestigial…6

5. Plants < 1 m tall...6

5. Plants > 1 m tall (there may be small individuals in a population generally > 1 m tall)...7

6. Inflorescence with expanded sheath(s) (inflated and out of proportion to the small size of the plant).  Leaf blades and sheaths usually glabrous.  Rames 2.8-4.2 cm long, usually exserted on peduncles 5-31 mm long.  Ligule 0.3-1.5 mm...

6. Inflorescence sheath not expanded; leaf blades and sheaths usually pubescent.  Rames 1.8-2.6 cm long, usually enclosed in leaf sheath or the peduncle < 4 mm...

7. Peduncles often > 14 cm.  Inflorescence branches (rames, racemes) 2.5-3.7 cm long.  Usually in scrub.  Inflorescence units numerous and crowded......

7. Peduncles usually < 14 cm.  Rames 1.7-2.8 cm long...8

8.  Inflorescense highly branched and dense.  Ligules 0.6-2.2 mm, ciliate.  Sheaths usually scabrous, < 2 mm wide.....

8. Inflorescence usually diffuse, not a dense mass at the top of the plant.  Ligules 0.1-1 mm,  membranous to sometimes ciliate.  Sheaths usually smooth, > 2 mm wide...

9. Lower glume pubescent or glabrous.  Upper glume cleft for > half its length.  Awn on sessile spikelet 15-25 mm….

9.  Lower glume glabrous.  Upper glume cleft for< half its length; awn on sessile spikelet < 17 mm…. 10

10. Awns on pedicellate spikelet absent-4 mm.  Blade 1.5-9 mm…

10. Awns on pedicellate spikelet to 1 mm.  Blade 1-6 mm wide…S. rhizomatum (syn. of S. scoparium in Wunderlin)

Aristida

1.  Lateral awns < 12 mm long, < half as long and half as thick as the central awn...

1.  Lateral awns 10 or more mm, > half the length of the central awn…2

2.  Inflorescence a dense foxtail > 15 mm wide (excluding awns) wide…

2.  Inflorescence otherwise…3

3.  Wetland grass with well developed scaly rhizome; upper glume with awn > (3)-7 mm… (basal sheath shredding) (central awn 15-30 mm long, horizontal to reflexed; lateral awn 13-20 mm)

3.  Wetland or dry habitat grass without strongly developed rhizome; upper glume with no awn or with awn < 3 mm long…4

4.  Leaf blades predominantly flat toward the base of the plant…5

4.  Leaf blades involute…6

5.  Leaf blades curled; lower glume < 9 mm long; ligule < 0.1 mm long; central awn 8-25 mm…

5.  Leaf blades usually not curled; lower glume > 9 mm long; ligule 0.2 mm long; central awn 15-40 mm long…

6.   Awns contorted (also true in A. purpurascens var. tenuispica with flat leaves and   equal glumes); glumes unequal; callus usually > 1 mm long; leaf collars glabrous; awns nearly equal…

6.   Awns not contorted; glumes nearly equal; callus usually 0.4-0.6 mm; leaf collars pubescent; lateral awns a little shorter than central awn…

 Axonopus

First glume missing (vs. Urochloa) but consistent with Digitaria.   Inflorescence nearly Y-shaped or with an extra branch or more below the Y (or the Y with 3 branches). Spikelets solitary (vs. usually in 2s or 3s in Digitaria); fertile lemma margins only weakly inrolled (vs. wrapped around in Digitaria)

Spikelets 1.6-3.5 mm; upper glume with pilose margin, 2-veined…

Spikelets > 3.5 mm; upper glume with glabrous margins, 5-7-veined… 

Bothriochloa

B. pertusa has a pit in the glume

B. ischaemum resembles Dichanthium, but Bothriochloa has a translucent groove in the rame axes.

Cenchrus

Recognize Cenchrus as the familiar painful beach sandspurs...grasses with porcupine burrs that stick in dog fur and human flesh! 

1. Spines with antrorse barbs, and setose...

1. Spines with retrorse barbs...2

2.  Spines of two distinct types: one type being a whorl of terete bristles at the base of the burr; the other bristles flat in one or more apparent whorls…

2.  Spines all flattened and not with a distinct ring of terete bristles at the base of the spikelet (can have some round in C. tribuloides, but this with a raceme 2 cm in diam. vs. smaller)…3

3.  Racemes > 2 cm diam…. (spikelet 1[2], 8-9 mm long)

3.  Racemes 1 cm diam….4

4.  Leaf blades usually 2(3.5) mm wide (well above the divergence from the sheath), glabrous; racemes usually not nestled in a subtending leaf sheath; ligule < 0.6 mm long; burrs uncrowded, with pubescence mostly confined to the spines, 3.5 mm diam…

4. Some leaf blades > 3 mm wide, often pubescent adaxially, the racemes often (not always) nestled in a leaf sheath; ligule > 0.5 mm long; burrs crowded or  uncrowded, usually pubescent on the outside at the base, 4-6 mm diam.…(C. pauciflora, C. longispinus)

Coelorachis

Rottboellia similar but with hispid nodes and sheaths

Hemarthria with similar but flattened (vs. cylindric) pencil-like raceme

1. Spikelets strongly rugose; rachis adjacent to the sessile spikelet bent; flowering spring-summer…

1. Spikelets smooth or nearly so; rachis adjacent to the sessile spikelet straight; flowering summer-autumn…

Dichanthelium

Dichanthelium resembles Panicum and is interpreted by many authors as belonging within Panicum.  Dichanthelium differs (with the exception of two species) by tending strongly toward two growth phases (which in South Florida are not always crisply differentiated):  an autumn-winter production of ground-hugging rosettes and a spring-summer production of bushy upright stems that branch and rebranch with fascicles of leafy shoots.  Interestingly, Dichanthelium has C3 photosynthesis and Panicum C4 photosynthesis with its associated Kranz anatomy.  In Dichanthelium the palea tips have papillae in regular rows, in contrast with irregularly arranged papillae in Panicum.  A full discussion of the differentiation of Dichanthelium is in the Gould & Clark reference in the Introduction.

1. Plants basal rosettes with little or no branching above the base even in the summer phase.  Leaf blades soft,  the margins ciliate for the entire length (the cilia pustule-based in D. strigosa).  Leaf sheath strongly pubescent…10

1. Plants usually branched above the base (Note: these species may form basal rosettes, and seasonally [winter phase] may exist in a rosette form, but usually substantial cauline branching is apparent,)  Leaf blades stiff, the margins usually entire or scabrous, or ciliate basally (but rarely ciliate for the entire length).  Leaf sheath glabrous, a little pubescent (or infrequently strongly pubescent)…2

2.  Lower glume 1/3 the spikelet length, truncate.  Leaf blades usually ciliate marginally toward the base; (2)2.5-7 cm long, 2-6 mm wide.  Spikelets 1.5-2.6 mm long; the comparatively long truncate glume is distinctive...  (The blunt lower glume is distinctive; D. ensifolium can also have a blunt glume)

2.  Plants not with the above combination of characters.  Lower glume broadly to sharply pointed...3

3. Leaf blades mostly 2-4(6) mm wide AND > 6 cm long.  Spikelets 1.7-3 mm long…

3. Leaf blades mostly wider than 4 mm OR < 6 cm long…4

4. Mid-stem leaf blades usually narrower than 3 mm (but rarely to 6 mm in D. aciculare), rounded to attenuate basally…5

4. Mid-stem leaf blades usually 3 mm wide or wider; bases often auriculate, or subcordate to cordate basally…6

5. Lower glume 1/3 the spikelet length.  Leaf blade with cartilaginous margin; ligule < 0.7 mm… (treated by Wunderlin as synonym of D. ensifolium)

(If D. tenue accepted as distinct, it differs from D. chamaelonche by having cauline blades flat vs. involute)

5. Lower glume ¼ the spikelet length (pointed or blunt).  Leaf blade with green margin; ligule 1 mm.  Lower glume blunt or pointed…

6. Leaves > 1 cm wide.  Culm > 0.5 m… (ligule membranous)

6. Leaves and culms smaller…7

7. Leaf blades mostly > 8 mm wide (at least at base of plant, others ranging to smaller sizes), often cordate…8

7. Leaf blades mostly 8 mm wide or narrower, the bases usually rounded to tapered…9

8. Spikelets < 1.4 mm long.  First glume1/5 the spikelet length…

8. Spikelets usually 2.2-2.8 mm long.  Ligule nearly absent or at least partly membranous…

9. Spikelets > 1.5-2 (rarely larger) mm long.  Ligule consisting solely of hairs.  Leaves usually about 8(14) mm wide.  Culms and abaxial leaf surfaces glabrous…

9. Spikelets 1.8-2.9 mm.  Ligule 2-layered.  Leaf blades 5-10 mm wide.  Culms and abaxial  leaf surface pubescent… (Culms and undersides of leaves glabrous in D. acuminatum and D. dichotomum)

 NOTE:  The following two species tend toward unusually soft leaves, ciliate along the margins, mostly tufted near ground level or not (or minimally) branched above the tuft.  Depending on the season and species, the other species in the present account are not usually (but can be) confined to ground-hugging tufts.

 10. Spikelets (1.7) 2.2-2.3 mm long, the hairs papillose-based.  Leaf sheaths with retrorse hairs (often strikingly hirsute). Uppermost stem leaves > ¾ as long as the basal leaves.  Blade margins ciliate with usually non-papillose cilia…

10. Spikelets 1.1-2.1 mm long, the pubescence not papillose-based;  leaf sheaths with ascending hairs (or glabrous); uppermost leaf blades < ¾ the length of the basal leaves; blade margins with papillose-based cilia…

Digitaria

(Note: Lower glume absent or very small)

1. Spikelets silky, 4.2-5.9 mm long…

1. Spikelets variably pubescent or not, < 4 mm long…2

2. Spikelets ≤ 2 mm long…3

2. Spikelets > 2 mm long…5

3.  Inflorescence branches 3-25 cm long.  Leaf blades to 40 cm long (but often much smaller).  Lower glume present.  Spikelet hairs glandular-capitate…

3.  Inflorescence branches 2-9 cm long.  Leaf blades 1.5-9 cm long.  Lower glume absent.  Spikelet hairs not glandular-capitate…4

4.  Spikelets 1.2-1.5 mm long.  Upper (only) glume as long as the spikelet or nearly so.  Leaf sheaths glabrous… (Looks like Paspalum conjugatum)

4. Spikelets 1.5-1.8 mm long.  Upper (only) glume 1/3 the spikelet length.  Leaf sheaths pubescent…

5. Spikelets 2.1-2.4 mm long…

5. Spikelets > 2.5 mm long…6

6. Upper glume < 1/3 the spikelet length…D. setigera (sheath with papillose-based hairs.  Lower glume absent;  recorded for Miami-Dade County,  unlikely in our area)

6. Upper glume > 1/3 the length of the spikelet…7

7. Lower lemma with the veins evenly spaced on the sessile spikelet.  Fresh young pedicellate spikelet margins with stiff, protruding bristles distinguished from smaller, thinner, softer hairs; not stoloniferous…

7. Lower lemma with the lateral veins crowded near the margin on the sessile spikelet.  Spikelet margins with soft cilia but no stiff protruding bristles.  Plants stoloniferous or not…8

8. Plants usually strongly stoloniferous with long runners.  Anthers > 1 mm long.  Ligule erose-cilioate.  Upper glume 1.7-1.9 mm long … (D. pentzii)

8. Plants stoloniferous or not stoloniferous.  Anthers < 1 mm long.  Ligules erose or entire and eciliate.  Upper glume (1.2)1.5-2.7 mm…

Echinochloa

(ligules absent in ours)

 1. Awn usually > 10 mm…5

1. Awn usually < 10 mm long, or absent…2

2. Lower floret usually staminate… (large grasses often > 1 m tall, having short awns)

2. Lower floret sterile…3

3. Spikelets with no awn (or second glume or sterile lemma with pointed caudate apex to 2 mm long).  Spikelet hairs not papillose-based; inflorescence branches not secondarily branches… (sheaths glabrous)

3. Spikelets awned; spikelet hairs papillose based or not; inflorescence branches with  secondary branchlets (at least in E. muricata)…4

4. Spikelet hairs with papillose bases… (sheaths glabrous)

4. Spikelet hairs not papillose…5

5. Sheaths usually glabrous or with soft hairs; awns 0-50 mm mm.  Fertile lemma with ring or tuft of trichomes near the tip, which tends to wither…(spikelet hairs may be papillose in extra-regional material)

5. Sheaths usually hispid; awn usually 10-25 mm.  Fertile lemma with no ring of trichomes near the tip, which is membranous but not withered..

 Eragrostis

In this genus, for keying it is important to use mature spikelets.  The spikelets continue to grow significantly after emergence of the inflorescence.

1.  Plants (sheaths, glumes, lemmas) glandular OR with long cilia on the paleas.  Inflorescences pencil-shaped or cylindric, usually < 4 cm in diameter…2

1. Plants not glandular, and paleas without long conspicuous marginal cilia (or with tiny cilia < 0.1 mm long). Inflorescences elliptic or ovate, usually (but not always) > 4 cm in diameter…4

2.  Leaf sheaths, glumes, and lemmas usually with glands.  Spikelets very wide (2-4 mm).  Lemmas > 2.5 mm long.  Paleas without long comblike cilia…(rare in our area if present at all)

2.  Leaf sheaths, glumes and lemmas without glands.  Spikelets usually < 2.5 wide; lemmas with long comblike cilia…3

3. Inflorescence narrow, so tightly congested as to hide the branches and pedicels, the shape and size of a pencil to cigar, resembling a furry tail (usually < 2 cm diam.)…

3. Inflorescence usually 1- 5(7) cm wid, cylindric … (usually encountered as a small weed in open, sandy, highly disturbed places)

4. Spikelet 2-4.6 mm X 0.9-2 mm.  Lemma 1-1.3 mm; anthers 2…

4.  Spikelet dimensions ranging above the above limits.  Anthers 2 or 3…5

5.  Glumes equal or nearly so, both glumes slightly longer than 1 mm (usually ca. 1.3 mm).  Leaf blades 3-8 mm wide. (Note:  glumes subequal also in E. atrovirens but its glumes 1.2-1.7 mm and the pulvinus glabrous. Glumes subequal may occur in E. scaligera but this with the inflorescence < 15 cm vs. > 25 cm long)… (Inflorescences often purplish, branch bases with a tuft of hairs, the bases often included in subtending leaf base.  Anthers 2)

5.  Glumes unequal, or if equal not ca. 1.3 mm long; leaf blades usually < 5 mm wide…6

6. Lower glume 0.3-0.6 mm… (glumes extremely unequal; spikelet usually < 6 mm long; anthers 3)

6. Lower glume > (0.5)0.7 mm…7

7. Pedicels longer than spikelets AND spikelets erect on branches…

7. Pedicels shorter than or equal to spikelets; spikelets usually appressed to branches (spikelets may angle our from branch but then the pedicels shorter than or equal to the spikelets)…8

8. Main inflorescence branches with long hairs at the base…

8. Main inflorescence branches glabrous (or nearly so) at the base…9

9. Culms > 75 cm tall with the lowest inflorescence branch > 30 cm above the basal leaves.  Leaf blades adaxially pilose.  Bases of inflorescences branches bare… (anthers 3)

9. Culms usually < 75 cm tall with the lowest inflorescence branches usually < 30 cm above the basal leaves. Leaf blades adaxially glabrous to ciliate.  Bases of inflorescence branches often hidden by spikelets, or bare) …10      [Eragrostis bahiensis infrequently exceeds 75 cm tall, but differs by having 2 vs.3 anthers, by ranging to more florets per spikelet (8-30 vs. 10-22 florets),  and by ranging to larger leaf blades less likely to be adaxially pilose: 12-40 cm X 2-5 mm vs. 8-20 cm vs. 2-3 mm.]

10. Spikelets overlapping along branches only basally (tip-to-tail, or not overlapping).  Inflorescence branches not branched (except occasionally at base).  Anthers 3…   [E. pectinacea differs from similar E. atrovirens by having adaxial leaf surfaces glabrous as opposed to ciliate.  Inflorescence usually as long as its own scape (vs. scape several times longer than the branching portion of the inflorescence).  Lemma 0.4-0.6 mm margin-to-keel vs. 0.6-0.8(0.9) mm.]

10. Spikelets overlapping along the inflorescence branches to the spikelet centers or beyond.  Anthers 2…11

11. Leaf blades 4-8 cm X 1-2 mm.  Lower glume > 1.4 mm.  Upper glume (1.6) > 1.7 mm. Inflorescence   5-15 cm X 2-10 cm…    (lemma 0.6-0.9 mm margin-to-keel vs. < 0.6 mm in E. pectinacea)

11. Leaf blades 12-40 cm X 2-5 mm.  Lower glume < 1.4 mm.  Upper glume < 1.7 mm; inflorescence 15-30 cm X 8-17 cm… (E. gangetica similar but with smaller spikelets (2-4.6 mm  vs. > 6 mm)