| 1. | Lemma with prominent awn | 2 |
| Lemma awnless, mucronate or shortly awned | 29 | |
| 2. | Awn at least twice spikelet length | 3 |
| Awn shorter than, as long as or slightly longer than spikelet length | 17 | |
| 3. | Palea awns separate, almost as long as lemma awns | E. triseta (NT WA QLD) |
| Palea awns absent or fused for some distance of their length and much shorter than lemma awns | 4 | |
| 4. | Inflorescence ±loose | 5 |
| Inflorescence dense | 12 | |
| 5. | Palea without awns | 6 |
| Palea with awns, fused somewhere along their length |
10 | |
| 6. | Spikelets (without awns) less than 5 mm long | 7 |
| Spikelets 7-8 mm long | 8 | |
| 7. | Spikelets c. 2 mm long | E. minuta (NT) |
| Spikelets 3-4 mm long | E. agrostidea (NT QLD) | |
| 8. | Inflorescence less than 5cm long | E. pauciflora (NT WA) |
| Inflorescence more than 5cm long | 9 | |
| 9. | Annual; leaf blades with vesicles on upper surface | E. basalis (NT QLD) |
| Perennial; leaf blades scabrous or glabrous on upper surface | E. burkittii (NT WA QLD) E. burkittii var. hirsutissima, E. laidlawii |
|
| 10. | Leaf-blades vesicular on upper surface | E. vesiculosa (NT QLD) |
| Leaf-blades not vesicular on upper surface | 11 | |
| 11. | Palea awns fused along most of their length | E. rara (NSW NT WA QLD) |
| Palea awns fused only at base | E. stipacea (NT QLD) | |
| 12. | Annual; palea awns fused only at base | E. armitii (NT WA QLD) |
| Perennial; palea awns fused for most of their length | 13 | |
| 13. | Glumes more than 8 mm long | 14 |
| Glumes 4-5 mm long | 16 | |
| 14. | Lemma obtuse without lateral grooves apically; culm internodes hairy to some degree | E. squarrosa (QLD) |
| Lemma acute, with lateral grooves apically; culm internodes glabrous | 15 | |
| 15. | Lemma hairy all over; palea c. 9 mm long | E. schultziana (NT) |
| Lemma hairy in lower half; palea c. 7 mm long | E. sulcata (NT WA) | |
| 16. | Nodes glabrous | E. glauca var. glauca (NT WA QLD) |
| Nodes bearded | E. glauca var. barbinodis (NT WA QLD) | |
| 17. | Spikelets (without awns) longer than 6 mm | 18 |
| Spikelets (without awns) to 5 mm long | 21 | |
| 18. | Annual | E. aristidea (NSW NT SA WA QLD) E. aristidea var. minor |
| Perennial | 19 | |
| 19. | Awns strongly recurved in mature spikelets | E. festucacea (NT WA QLD) |
| Awns straight in mature spikelets | 20 | |
| 20. | Lemma pilose on margins; awn shorter than lemma; leaf-blades filiform | E. avenacea (NT WA) E. setacea |
| Lemma pilose all over back; awn as long as lemma; leaf-blades flat to involute | E. triodioides (NT WA QLD) | |
| 21. | Perennial | 22 |
| Annual | 24 | |
| 22. | Lemma with a groove in the upper glabrous part near both margins |
E. imbricata (WA) |
| Lemma without grooves | 23 | |
| 23. | Spikelets normally 1-flowered | E. pallescens var. gracilis (QLD) E. anomala |
| Spikelets normally 2-flowered | E. pallescens var. pallescens (QLD) E. muelleri, E. yarrabensis |
|
| 24. | Inflorescence very open; leaf-blades usually flat; spikelets (excluding awns) up to 3.5 mm long | 25 |
| Inflorescence contracted to some degree; leaf-blades usually involute; spikelets 3.5 mm or more long | 27 | |
| 25. | Spikelets c. 2.5 mm long; awns shorter than lemma | E. sp. C (Dugald River, Simon 3007) (NT WA QLD) |
| Spikelets 3-3.5 mm long; awns as long as lemma | 26 | |
| 26. | Glumes acuminate, longer than wide; florets slightly shorter than glumes; lemma ciliate on margins for their entire length; hairs on culms and foliage chiefly antrorse |
E. ciliata (NT WA QLD) |
| Glumes obtuse, almost as wide as long; florets equal to glumes or slightly longer; lemma glabrous on margins near apex; hairs on culms and foliage chiefly retrorse | E. semiciliata (NT WA) | |
| 27. | Inflorescence in tight clusters | E. compacta (NT) |
| Inflorescence loosely contracted | 28 | |
| 28. | Lemma (excluding awn) 2-3 mm long, with awn longer than lemma | E. filiformis (NT QLD) |
| Lemma 3.25-4 mm long, with awn shorter than lemma | E. humilis (NT QLD) | |
| 29. | Spikelets to 2 mm long | E. capillaris (NT) |
| Spikelets more than 2 mm long | 30 | |
| 30. | Lemma more than 10 mm long | E. nervosa (WA NT QLD) |
| Lemma less than 10 mm long | 31 | |
| 31. | Annual | 32 |
| Perennial | 37 | |
| 32. | Inflorescence a spicate panicle | 33 |
| Inflorescence an open panicle | 35 | |
| 33. | Lemma not ciliate on margins | E. fastigiata (WA NT) |
| Lemma ciliate on margins | 34 | |
| 34. | Inflorescence densely spicate, up to 3.5 cm long when mature |
E. pulchella subsp. pulchella (NSW NT SA WA QLD) E. insigniana |
| Inflorescence loosely spicate, more than 3.5 cm long when mature | E. pulchella subsp. dominii (NT WA QLD) | |
| 35. | Spikelets less than 3.5 mm long | E. axillaris (NT) |
| Spikelets more than 3.5 mm long | 36 | |
| 36. | Spikelets c. 7 mm long | E. melicacea (NT WA QLD) |
| Spikelets c. 5 mm long | E. nodosa (NT WA) | |
| 37. | Inflorescence reduced to 1-2 spikelets; culm internodes woolly and completely covered by leaf sheaths | E. scleranthoides (NT WA QLD) |
| Inflorescence of few to numerous spikelets; culm internodes not as above | 38 | |
| 38. | Butt distinctly thickened and very woolly | 39 |
| Butt, if thickened and/or woolly, only slightly so | 40 | |
| 39. | Inflorescence open | E. helmsii (NSW NT SA WA QLD) |
| Inflorescence densely spicate | E. basedowii (NT) | |
| 40. | Lemma 7-9 mm long | 41 |
| Lemma less than 7 mm long | 47 | |
| 41. | Lemmas distinctly longer than glumes | 42 |
| Lemmas subequal or slightly longer than glumes |
44 | |
| 42. | Lemmas glabrous | E. tenuiculmis (WA) E. pallida |
| Lemmas pilose | 43 | |
| 43. | Glumes 9-11-nerved; lemmas grooved; panicle branches not capillary |
E. benthamii (NT SA WA QLD) |
| Glumes 7-nerved; lemmas not grooved; panicle branches capillary | E. bleeseri (NT) | |
| 44. | Inflorescence ±loose | E. gardneri (WA) |
| Inflorescence congested | 45 | |
| 45. | Inflorescence with swollen yellowish glands on rachis | E. glandulosa (NT WA) |
| Inflorescence without glands | 46 | |
| 46. | Panicle usually ovate and dense | E. ovata (SA WA) E. ovata var. villosa |
| Panicle often irregular | E. flaccida (NT WA) | |
| 47. | Lemma with an acute apex | 48 |
| Lemma with a mucronate apex | 50 | |
| 48. | Lemmas glabrous | E. glabrata (NSW QLD) |
| Lemmas hairy | 49 | |
| 49. | Glumes 3/4 spikelet length; panicle open |
E. lanata (WA) |
| Glumes ±as long as spikelet; panicle ±congested |
E. obtusa (NT WA QLD) E. obtusa var. major, E. major |
|
| 50. | Spikelets c. 3 mm long; panicle open | E. insularis (QLD) |
| Spikelets 5-6 mm long; panicle ±congested | 52 | |
| 52. | Culms 4-6 noded; leaf-blades to 4cm long |
E. mucronata typical form (NSW NT SA WA QLD) |
| Culms more than 6 noded; leaf-blades less than 1.5 cm long |
E. mucronata desert form (NT QLD) |
Key to Eriachne derived from Bentham 1878; Lazarides 1995; Lazarides et al 2005
Taxonomic name: