Inflorescence of slender spike-like racemes digitately or subdigitately arranged.
Spikelets in groups of 2 or 3, 1 subsessile and the other(s) shortly pedicellate, alternate in 2 rows on 1 side of the axis, closely appressed to it, dorsally compressed, falling entire; florets 2, the lower sterile, the upper bisexual. Glumes not alike, the lower minute, sometimes absent, the upper 3–5-nerved, rarely 1-nerved or nerveless. Lemmas 2, the lower usually as large as the upper lemma, 7- or 8-nerved, rarely 3-nerved, usually hairy, nerves parallel and prominent; upper lemma firm with hyaline margins, covering most of the back of the palea, faintly 3-nerved. Paleas 2, the lower minute, the upper equal to the upper lemma,
| | Key to the species | |
| 1 | Racemes very long, rigid, spreading and diverging at maturity, the basal 2–12 cm of each raceme without spikelets (rarely with a few spikelets at the base then bare for several cm), lower branches whorled | 2 |
| Racemes long or short, usually not stiff, with spikelets at the base, rarely bare for a few mm (or up to 2 cm in D. brownii); lower branches ± whorled | 6 |
| 2 | Spikelets 2–3.5 mm long; spikelets with silky hairs up to 2.5 mm long that obscure the outline; leaves greyish-pubescent | 3 |
| Spikelets 3.5–5 mm long, hairs present but not usually obscuring the spikelet outline; leaves ± greyish-pubescent
Back to 1 | 4 |
| 3 | Spikelets c. 2.5 mm long; upper glume and sterile lemma villous (with long wavy hairs) on the back, both base and apex being obscured by hairs | Digitaria ammophila |
| Spikelets c. 3–3.5 mm long with hairs on the sides and back of the upper glume and lower lemma but not obscuring the base and apex, stiff bristles also present
Back to 2 | Digitaria hystrichoides |
| 4 | Spikelets 3.75–5 mm long, acute, upper glume slightly shorter and narrower than the spikelet and not conspicuously separated from the lower glume; short hairs 0.5 mm long in raceme axils | Digitaria divaricatissima |
| Spikelets c. 5 mm long, appearing obtuse because of the spreading hairs; upper glume subequal to the spikelet and arising a little above the lower glume; hairs in branch axils 1–3 mm long; foliage greyish-pubescent
Back to 2 | 5 |
| 5 | Racemes not branched | Digitaria coenicola |
| Lower whorled racemes often unilaterally branched
Back to 4 | Digitaria porrecta |
| 6 | Sterile lemma with two prominent tufts of silky hairs a little below the middle of each side of the mid-nerve; upper glume silky-hairy | Digitaria hubbardii |
| Sterile lemma without conspicuous hair tufts; upper glume ± hairy
Back to 1 | 7 |
| 7 | Spikelets almost concealed by long silky hairs on the upper glume and lower lemma | 8 |
| Spikelets ± hairy but hairs not concealing the spikelets, hairs shorter than the spikelet and not usually silky
Back to 6 | 9 |
| 8 | Lower glume minute and hyaline or absent | Digitaria leucostachya |
| Lower glume firm, usually acute, up to 30% as long as the spikelet
Back to 7 | Digitaria brownii |
| 9 | Spikelets mostly ternate (borne in groups of three) pedicels arise at one point but longest pedicel may be partly fused with the rhachis giving the appearance of alternately paired and single arrangement | 10 |
| Most spikelets borne in pairs; spikelets may appear ternate if one pedicel is branched
Back to 7 | 13 |
| 10 | Spikelets <2 mm long; fertile lemma pale to purplish-black at maturity; pedicels without a ring of hairs at the apex; racemes digitate or subdigitate; spikelet hairs usually verrucose (sprinkled with tiny grains) | 11 |
| Spikelets 2 mm or longer, fertile lemma purplish-black at maturity; ring of hairs often present at the top of the pedicel; some hairs on upper glume and lower lemma with club-shaped or coiled tips, not verrucose; racemes variously arranged
Back to 9 | 12 |
| 11 | Fertile floret purplish-black, racemes 2–13 | Digitaria violascens |
| Fertile floret pale or brown, not purplish-black, racemes 2–3 (rarely more)
Back to 10 | Digitaria longiflora |
| 12 | Pedicels with a ring of short hairs at the apex (visible when the spikelets have fallen) | Digitaria ternata |
| Ring of hairs not present at the top of the pedicel
Back to 10 | Digitaria ischaemum |
| 13 | Upper glume equal to or subequal to the spikelet | 14 |
| Upper glume up to 75% the length of the spikelet
Back to 9 | 16 |
| 14 | Spikelets 2.5–3.5 mm long; lower glume absent; racemes digitate of subdigitate (the common axis up to 1 cm long) | Digitaria aequiglumis |
| Spikelets 1.5–2.2 mm long; lower glume minute to 25% the length of the spikelets; racemes arising from a common axis 3–10 cm long
Back to 13 | 15 |
| 15 | Spikelets glabrous on internerves and margins of upper glume and lower lemma with a few appressed hairs; tufted perennial with culms to c. 1.5 m tall | Digitaria parviflora |
| Spikelets with hairs between the nerves of upper glume and lower lemma, at first appressed but later spreading and conspicuous, white or purple; delicate plants rooting at lower nodes, culms up to 40 cm tall
Back to 14 | Digitaria diffusa |
| 16 | Upper glume <50% as long as the spikelet (usually up to 30% as long) | 17 |
| Upper glume >50% the length of the spikelet (if<50% then the spikelet at least 2.5 mm long)
Back to 13 | 18 |
| 17 | Lower glume absent, upper glume 10–25% as long as the spikelet | Digitaria orbata |
| Lower glume present, often very small; upper glume 25–35% as long as the spikelet
Back to 16 | Digitaria breviglumis |
| 18 | Spikelets not more than 2.75 mm long; perennials | 19 |
| Spikelets 2.75–3.5 mm long; hairy annuals
Back to 16 | 22 |
| 19 | Racemes digitate, 2–3; slender stoloniferous perennial often forming a dense turf | Digitaria didactyla |
| Racemes 3–15 on a primary axis 3–10 cm long
Back to 18 | 20 |
| 20 | Upper glume acute; sterile lemma as long as spikelet | Digitaria velutina |
| Upper glume obtuse; sterile lemma usually slightly shorter than spikelet
Back to 19 | 21 |
| 21 | Margins and internerves of upper glume and lower lemma glabrous or with very short hairs; short hairs in axils of racemes | Digitaria ramularis |
| Margins and internerves of upper glume and lower lemma hairy; long hairs in axils of branches
Back to 20 | Digitaria sp. aff.ramularis |
| 22 | Upper glume 30–50% as long as the spikelet; nerves of the lower lemma scaberulous (sometimes with bristles) and evenly spaced | Digitaria sanguinalis |
| Upper glume 50–75% as long as the spikelet; nerves of the lower lemma smooth, usually with a wide interspace on each side of the mid-nerve; spikelets often with a ciliate frill (hard to distinguish from D. sanguinalis)
Back to 18 | Digitaria ciliaris |
