| 1. | Lateral awns less than 1/3 as long as median awn or absent | 2 |
| Lateral awns as long as median awn or more than 1/3 its length | 5 | |
| 2. | Awns relatively thick, the central c. 5 mm long; lemma convolute | A. thompsonii (QLD) |
| Awns relatively thin, the central at least 7 mm long; lemma involute | 3 | |
| 3. | Lower internodes glabrous; leaf blades setaceous | A. spuria (NSW QLD) |
| Lower internodes hairy; leaf blades flat | 4 | |
| 4. | Lemma to 12mm long; glumes to 12 mm long | A. utilis var. utilis (NT QLD) A. streptachne |
| Lemma more than 17 mm long; glumes more than 15 mm long | A. utilis var. grandiflora (QLD) | |
| 5. | Lemma with an articulation | 6 |
| Lemma without an articulation | 13 | |
| 6. | Glumes inverse (lower longer than upper) | A. polyclados (NT WA QLD) |
| Glumes normal (not inverse) | 7 | |
| 7. | Awns dissimilar, median thicker and usually recurved, laterals slender usually erect and up to 2 cm shorter | 8 |
| Awns ± similar and erect, laterals as long as median or shorter by 2-5 mm | 10 | |
| 8. | Lateral awns much thinner than median and c. 1/2 length | A. granitica (QLD) |
| Lateral awns slightly thinner than median and more than 1/2 length | 9 | |
| 9. | Annual plant 35-50 cm tall; lemma 6-7.5 mm long | A. dominii (NT WA QLD) A. hirta auct. |
| Perennial plant 60-120 cm tall; lemma 8-12.5 mm long | A. superpendens (NT QLD) A. hirta |
|
| 10. | Column 5.5-8 cm long, c. 1 mm thick | A. hygrometrica (NT WA QLD) |
| Column usually less than 5 cm long, occasionally longer (to 6.5 cm) but then thinner (to 0.3 mm thick) | 11 | |
| 11. | Culms ± wavy; lemma (including callus) 5-7 mm long, brownish when mature | A. contorta (NSW VIC NT SA WA QLD) A. arenaria |
| Culms ± straight; lemma (including callus) 7-10 mm long, purplish when mature | 12 (A. holathera) |
|
| 12. | Leaf blades to 1.5 mm wide, involute | A. holathera var. holathera (NSW VIC NT SA WA QLD) A. browniana var. browniana, A. muelleri |
| Leaf blades more than 3 mm wide, flattened | A. holathera var. latifolia (NT WA) A. browniana var. latifolia |
|
| 13. | Lemma involute, with a furrow on ventral surface of caryopsis | 14 |
| Lemma convolute, without a furrow on ventral surface of caryopsis | 40 | |
| 14. | Lemma column present | A. perniciosa (NSW WA QLD) |
| Lemma column absent | 15 | |
| 15. | Awns unequal, laterals 1/2-2/3 as long as median | 16 |
| Awns ± equal or laterals more than 2/3 as long as median | 17 | |
| 16. | Culm internodes with pilose hairs, especially at base | A. queenslandica var. queenslandica (NSW NT QLD) |
| Culm internodes glabrous | A. queenslandica var. dissimilis (NSW QLD) A. dissimilis |
|
| 17. | Margins of lemma furrow with one to several rows of tubercles | 18 |
| Margins of lemma furrow smooth or lemma muricate towards apex | 26 | |
| 18. | Glumes inverse | 19 |
| Glumes subequal or normal | 23 | |
| 19. | Glumes differing in length by more than 2 mm | 20 |
| Glumes differing in length by less than 2 mm | 21 | |
| 20. | Lemma with a pseudo-articulation; leaf blades curling up on maturity | A. inaequiglumis (NSW SA WA QLD) |
| Lemma without a pseudo-articulation; leaf blades straight or flexuous | A. pruinosa (NT WA QLD) | |
| 21. | Glumes smooth, (8-)10-14 mm long; lemma 8-10mm long | A. calycina var. praealta (NSW QLD) A. armata, A. prealta |
| Glumes scaberulous, 5-9(-12) mm long; lemma 5.5-7 mm long | 22 | |
| 22. | Lateral awns shorter than median by more than 2 mm | A. benthamii var. spinulifera (QLD) |
| Lateral awns shorter than median by 1-2 mm | A. jerichoensis var. subspinulifera (NSW NT SA QLD) | |
| 23. | Lemma 10-12 mm long | A. biglandulosa (NT SA QLD) A. biglandulosa var. laevis |
| Lemma up to 9 mm long | 24 | |
| 24. | Lemma 4-5.5 mm long, much shorter than glumes, with a pseudo-articulation | A. helicophylla (QLD) |
| Lemma 6-9 mm long, subequal to glumes, without a pseudo-articulation | 25 | |
| 25. | Glumes smooth, (8-)10-14 mm long; lemma 8-10 mm long | A. calycina var. praealta (NSW QLD) A. armata, A. prealta |
| Glumes scaberulous, 5-9(-12) mm long; lemma 5.5-7 mm long | A. jerichoensis var. subspinulifera (NSW NT SA QLD) | |
| 26. | Lemma with a pseudo-articulation | 27 |
| Lemma without a pseudo-articulation | 28 | |
| 27. | Glumes differing in length by more than 3 mm | A. inaequiglumis (NT SA WA QLD) |
| Glumes differing in length by less than 3 mm | A. ingrata (NT WA QLD) | |
| 28. | Lemma muricate towards apex | 29 |
| Lemma smooth | 32 | |
| 29. | Annual or short lived perennial usually less than 30 cm tall; inflorescence a densely congested spike | A. anthoxanthoides (NSW NT SA WA QLD) |
| Perennials more than 50 cm tall; inflorescence a loosely arranged spike | 30 | |
| 30. | Lower glume 3-nerved | A. exserta (NT WA QLD) |
| Lower glume 1-nerved | 31 | |
| 31. | Glumes to 4.5 mm long; lemma awns to 6 mm long |
A. forsteri (QLD) |
| Glumes to 12 mm long; lemma awns to 30 mm long |
A. muricata (NSW QLD) | |
| 32. | Lemma margins distinctly protruding from ventral furrow | A. lazaridis (NT WA QLD) |
| Lemma margins not protruding or if so, not distinctly | 33 | |
| 33. | Glumes more than 13 mm long | 34 |
| Glumes less than 12 mm long | 35 | |
| 34. | Lower glume 3-nerved | A. sciuroides (QLD) A. borealis |
| Lower glume 1-nerved | A. biglandulosa (NT SA QLD) A. biglandulosa var. laevis |
|
| 35. | Lateral awns shorter than median by 1-2 mm | A. jerichoensis var. jerichoensis (NSW QLD) |
| Lateral awns shorter than median by more than 2 mm | 36 | |
| 36. | Lemma 3.5-5.5 mm long | A. benthamii var. benthamii (NSW TAS QLD) |
| Lemma more than 6 mm long | 37 | |
| 37. | Lower glume 3-nerved | A. sciuroides (QLD) A. borealis |
| Lower glume 1-nerved | 38 | |
| 38. | Glumes acuminate to awned; inflorescence branches usually naked in lower 1/2 | A. acuta (NSW QLD) |
| Glumes acute to obtuse; inflorescence branches usually bearing spikelets from base | 39 | |
| 39. | Leaf blades filiform and arranged basally on culm | A. calycina var. filifolia (QLD) |
| Leaf blades not as above | A. calycina var. calycina (NSW VIC NT WA QLD) A. glumaris |
|
| 40. | Lemma with a twisted column (sometimes reduced to a 1/2 spiral) | 41 |
| Lemma without a column | 48 | |
| 41. | Lower glume 3-7-nerved | 42 |
| Lower glume 1-nerved | 43 | |
| 42. | Awns similar | A. schultzii (NT QLD) |
| Awns dissimilar, median thicker and recurved at maturity | A. warburgii (NSW QLD) A. heterochaeta, A. intricata |
|
| 43. | Glumes differing in length by up to 2 mm | A. latifolia (NSW NT SA WA QLD) |
| Glumes differing in length by up to 3-4 mm | 44 | |
| 44. | Inflorescence loose to open with branches naked at base | 45 |
| Inflorescence ± spike-like with branches bearing spikelets from base | 46 | |
| 45. | Column of many spirals | A. macroclada subsp. queenslandica (QLD) |
| Column of 1/2-1 spiral | A. macroclada subsp. macroclada (NT QLD) A. novaeguineae |
|
|
46.
47. |
Column of at least 1 complete spiral; lemma scabrous on margin apically |
A. psammophila (NSW QLD) |
| Column of a 1/2 spiral; lemma scabrous all over apically |
47 |
|
| Lemma scabrous all over apically; lemma awns 15-25 mm long; inflorescence 3-6 mm wide | A. longicollis(NT QLD) | |
| Lemma not scabrous apically or if so only on one margin; lemma awns 9-18 mm long; inflorescence 0.5-2 cm wide |
A. jacobsiana (NT QLD) |
|
| 48. | Spikelet (excluding awns) up to 3 mm long | A. cumingiana (QLD) |
| Spikelet (excluding awns) more than 5 mm long | 49 | |
| 49. | Lemma extended beyond both glumes | 50 |
| Lemma not extended beyond both glumes | 58 | |
| 50. | Lower glume c. 4mm long; upper glume less than 7 mm long | 51 |
| Lower glume more than 5 mm long; upper glume more than 7mm long | 52 | |
| 51. | Inflorescence 3-7 x 1-4 cm, ovate in outline | A. caput-medusae (NSW QLD) |
| Inflorescence larger, irregular in outline | A. vagans (NSW QLD) | |
| 52. | Culms bushy with many fine branches | A. gracilipes (NSW QLD) |
| Culms not bushy, if much branched then robust, otherwise slender with few branches | 53 | |
| 53. | Glumes acute to shortly aristulate | 54 |
| Glumes distinctly aristulate | 56 | |
| 54. | Inflorescence loose to open | A. personata (NSW SA QLD) A. ramosa var. speciosa |
| Inflorescence ± contracted or with branches which are ± contracted | 55 | |
| 55. | Lemma ± twice length of glumes | A. ramosa x A. vagans (NSW) |
| Lemma slightly longer than glumes | A. ramosa (NSW VIC SA WA QLD) | |
| 56. | Lemma scabrous all over apically; culms very robust and woody | A. lignosa (NSW QLD) |
| A. sp. Keep River N.P. | ||
| Lemma scabrous only on margin apically; culms slender to robust | 57 | |
| 57. | Culms 25-45cm tall with inflorescence 5-8 cm long | A. leichhardtiana (NSW QLD) |
| Culms 60-120cm tall with inflorescence 10-30 cm long | A. personata (NSW SA QLD) A. ramosa var. speciosa |
|
| 58. | Lower glume longer than or subequal to upper glume, 3-nerved | A. kimberleyensis (WA) |
| Lower glume shorter than or equal to upper glume, 1-nerved | 59 | |
| 59. | Lemma shorter than or equal to upper glume | 60 |
| Lemma shorter than or subequal to lower glume | 69 | |
| 60. | Upper glume more than 12 mm long | 61 |
| Upper glume less than 12 mm long | 64 | |
| 61. | Inflorescence longer than wide | A. vickeryae (NSW) |
| Inflorescence ± as long as wide | 62 | |
| 62. | Inflorescence 14-25 cm long and almost as wide; spikelets terminal on inflorescence branches | A. leptopoda (NSW QLD) |
| Inflorescence 6-12 cm long and wide; spikelets evenly distributed in inflorescence | 63 | |
| 63. | Peduncle terete; lemma ± smooth | A. behriana (NSW VIC SA) |
| Peduncle compressed; lemma densely scabrous | A. obscura (NSW NT SA WA QLD) | |
| 64. | Lemma tuberculate apically | A. echinata (NSW QLD) A. ramosa var. scaberula |
| Lemma smooth or scabrous to some degree apically | 65 | |
| 65. | Lemma scaberulous apically | A. longicollis (NT QLD) |
| Lemma smooth or slightly or marginally scabrous apically | 66 | |
| 66. | Glumes acute to shortly aristulate | 67 |
| Glumes distinctly aristulate | 68 | |
| 67. | Inflorescence ± contracted | A. ramosa (NT QLD) |
| Inflorescence loose to open | A. personata (NSW SA QLD) A. ramosa var. speciosa |
|
| 68. | Culms 25-45 cm tall with inflorescence 5-8 cm tall | A. leichhardtiana (NT QLD) |
| Culms 60-120 cm tall with inflorescence 10-30 cm tall | A. personata (NSW SA QLD) A. ramosa var. speciosa |
|
| 69. | Lemma smooth or minutely scaberulous or scabrous only along margins | 70 |
| Lemma tuberculate to distinctly scabrous all over apically | 74 | |
| 70. | Inflorescence loose and open; annual | A. annua (QLD) |
| Inflorescence spicate; perennials | 71 | |
| 71. | Lemma smooth with a marginal band of spines | A. burbidgeae (WA) |
| Lemma smooth all over or minutely scaberulous | 72 | |
| 72. | Glumes unequal; leaves flat to convolute, not rigid | A. australis (SA) |
| Glumes ± equal; leaves filiform and rigid | 73 | |
| 73. | Lemma 7-9 mm long with flattened awns | A. latzii (NT) |
| Lemma c. 6 mm long with slender awns | A. burraensis (QLD) | |
| 74. | Inflorescence loose and open | A. blakei (NSW NT QLD) |
| Inflorescence congested to spicate | 75 | |
| 75. | Lemma tuberculate-spiny | 76 |
| Lemma distinctly scabrous | 78 | |
| 76. | Lemma less than 6 mm long; leaf blades flat and curly | A. platychaeta (NSW QLD) |
| Lemma more than 6.5 mm long; leaf blades filiform or conduplicate or if flat not curly | 77 | |
| 77. | Glumes ± equal | A. nitidula (NSW NT SA WA QLD) |
| Glumes unequal | A. arida (NT SA) | |
| 78. | Lemma 8.5-12 mm long; leaf blades conduplicate or flat | A. strigosa (NSW NT SA WA QLD) |
| Lemma 5-8.5 mm long; leaf blades filiform | A. capillifolia (NT SA WA) |
Key to Aristida derived from Lazarides 1980b; Simon 1984b, 1986c, 1992b, 1994; Simon 2005
Taxonomic name: