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. strigosum). 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...D. portoricense (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. Ligule (at least part of it) > 2 mm long...D. acuminatum

3. Ligule < 2 mm long...4

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

4. Leaf blades mostly wider than 4 mm OR < 6 cm long…5

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

5. Mid-stem leaf blades usually 3 mm wide or wider; bases often auriculate, or subcordate to cordate basally…7

6. Lower glume 1/3 the spikelet length. Leaf blade with cartilaginous margin; ligule < 0.7 mm…D. chamaelonche (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)

6. Lower glume ¼ the spikelet length. Leaf blade with green margin; ligule 1 mm. Lower glume blunt or pointed…D. ensifolium

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…D. erectifolium

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

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…D. dichotomum

9. Spikelets 1.8-2.9 mm. Ligule 2-layered. Leaf blades 5-10 mm wide. Culms and abaxial leaf surface pubescent…D. ovale (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…D. laxiflorum

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…D. strigosum