Leaves either in a basal tuft or mostly on the culms; ligule usually a row of very short hairs; blade rolled in the bud.
Spikelets pedicellate, narrow, 1 bisexual floret, rachilla disarticulating above the glumes. Glumes equal or unequal, narrow, acute, acuminate or subulate, 1–3-nerved, keeled, mucronate or entire. Lemma hardened, convolute or apparently involute, narrow, 3-nerved, callus sharp and shortly bearded, apex terminating in a 3-branched awn with or without a distinct column. Palea small, 2-nerved.
Not valuable to fodder except during droughts. The 'seeds' (diaspores or units of dispersal) with a very sharp callus cause damage to animal hides and contaminate wool. Note: relative length of the glume applies to the condition in the intact spikelet, not with the glumes removed and length compared.
| | Key to the species | |
| 1 | Lateral awns less than 30% as long as the central awn, different in texture from it and thin | Aristida spuria |
| Lateral awns well-developed or, if shorter, over 30% as long as the central awn and similar in texture to it | 2 |
| 2 | Articulation (swollen joint) present between lemma and awn or column of awn | 3 |
| Articulation absent on the lemma (awn persistent or breaking at no particular place)
Back to 1 | 4 |
| 3 | Column 10–18(–25)mm long; lemma 5–7 mm long, brownish when mature; plants 10–30(–50) cm high | Aristida contorta |
| Column (16–)28–40 mm long; lemma 7–10 mm long, purplish when mature; plants 30–60 cm high
Back to 2 | Aristida holathera |
| 4 | Lemma involute, with a furrow on the ventral surface (sometimes the margins shows tendency to be convolute but the ventral furrow is distinct); grain with a well-developed ventral furrow | 5 |
| Lemma convolute, without a ventral furrow; grain with or without a very shallow furrow
Back to 2 | 14 |
| 5 | Awns unequal in length, laterals 30–65% as long as median | Aristida queenslandica |
| Awns more or less equal in length, or laterals more than 70% as long as median
Back to 4 | 6 |
| 6 | Margins of involute lemma with rows of distinct short spines (tubercles) more prominent in the upper part of the groove | 7 |
| Margins of the lemma furrow smooth or scabrous but without tubercles
Back to 5 | 9 |
| 7 | Glumes inverse i.e. the lower longer than the upper (var. praealta) | Aristida calycina |
| Glumes subequal or normal (lower shorter than upper), rarely inverse
Back to 6 | 8 |
| 8 | Lemma 6–9 mm long, subequal to glumes, without a pseudo-articulation (var. subspinulifera) | Aristida jerichoensis |
| Lemma 4–5.5 mm long, much shorter than the glumes, with a pseudo-articulation
Back to 7 | Aristida helicophylla |
| 9 | Lemma muricate (with protuberances) towards the apex | 10 |
| Lemma smooth
Back to 6 | 11 |
| 10 | Inflorescence a dense, spike-like panicle; plants usually less than 30 cm high, annuals | Aristida anthoxanthoides |
| Inflorescence more loosely arranged; plants usually more than 50 cm high, perennials
Back to 9 | Aristida muricata |
| 11 | Lateral awns shorter than the central awn by 1–2 mm; upper glume 8 mm long with an acute, entire apex (var. jerichoensis) | Aristida jerichoensis |
| Lateral awns shorter than the central awn by more than 2 mm; upper glume more or less acute, entire
Back to 9 | 12 |
| 12 | Lemma 3.5–5.5 mm long; upper glume 5–6 mm long with a 2-fid apex and a mucro between the lobes | Aristida benthamii |
| Lemma more than 6 mm long, upper glume entire
Back to 11 | 13 |
| 13 | Glumes acuminate to awned, distinctly inverse | Aristida acuta |
| Glumes acute to obtuse, subequal, normal; inflorescence branches bearing spikelets from near their bases
Back to 12 | Aristida calycina |
| 14 | Column of half to several spirals between the lemma apex and the awns | 15 |
| Column absent, the awns borne directly on lemma apex
Back to 4 | 17 |
| 15 | Lower glume 3-nerved | Aristida warburgii |
| Lower glume 1-nerved
Back to 14 | 16 |
| 16 | Lower glume less than 8 mm long, glumes differing in length by up to 2 mm | Aristida psammophila |
| Lower glume more than 8 mm long, glumes differing in length by 3–4 mm
Back to 15 | Aristida latifolia |
| 17 | Lemma extended beyond both glumes | 18 |
| Lemma not extended beyond both glumes
Back to 14 | 24 |
| 18 | Lower glume c. 4 mm long, upper glume less than 7 mm long | 19 |
| Lower glume more than 5 mm long, upper glume more than 7 mm long
Back to 17 | 20 |
| 19 | Inflorescence 3–7 cm long, 1–4 cm wide, oblong-ovate in outline | Aristida caput-medusae |
| Inflorescence larger, irregular in outline
Back to 18 | Aristida vagans |
| 20 | Culms bushy with many fine branches | Aristida gracilipes |
| Culms not bushy, if much-branched then robust, otherwise slender with few branches
Back to 18 | 21 |
| 21 | Glumes acute to shortly aristulate | Aristida ramosa |
| Glumes prominently aristulate
Back to 20 | 22 |
| 22 | Lemma scabrous-tuberculate; culms very robust | Aristida lignosa |
| Lemma scabrous only on the margins near the apex; culms slender to robust
Back to 21 | 23 |
| 23 | Culms 25–45 cm high; inflorescence 5–11 cm long | Aristida leichhardtiana |
| Culms 60–120 cm high; inflorescence 10–30 cm long (var. speciosa)
Back to 22 | Aristida ramosa |
| 24 | Lemma shorter than or subequal to the upper glume | 25 |
| Lemma shorter than or subequal to the lower glume
Back to 17 | 33 |
| 25 | Upper glume more than 12 mm long | 26 |
| Upper glume less than 12 mm long
Back to 24 | 29 |
| 26 | Inflorescence longer than wide | Aristida vickeryae |
| Inflorescence about as wide as long
Back to 25 | 27 |
| 27 | Inflorescence 14–30 cm long and almost as wide; spikelets terminal in inflorescence branches | Aristida leptopoda |
| Inflorescence 6–12 cm long and wide; spikelets evenly distributed on the branches
Back to 26 | 28 |
| 28 | Peduncle terete (cylindrical), inflorescence dense; lemma almost smooth | Aristida behriana |
| Peduncle compressed (flattened), inflorescence more open; lemma densely scabrous
Back to 27 | Aristida obscura |
| 29 | Lemma apex tuberculate (var. scaberula) | Aristida ramosa |
| Lemma smooth or scabrous at the apex, not tuberculate
Back to 25 | 30 |
| 30 | Lemma distinctly scabrous in the upper 60% | Aristida longicollis |
| Lemma smooth or scabrous only on the apical margins
Back to 29 | 31 |
| 31 | Glume tips acute to shortly aristulate (var. speciosa) | Aristida ramosa |
| Glume tips prominently aristulate
Back to 30 | 32 |
| 32 | Culms 25–45 cm high; inflorescence 5–8 cm long | Aristida leichhardtiana |
| Culms 60–120 cm high; inflorescence 10–30 cm long
Back to 31 | Aristida ramosa |
| 33 | Inflorescence loose and open | Aristida blakei |
| Inflorescence dense or spike-like
Back to 24 | 34 |
| 34 | Lemma to 6.5 mm long; leaves with blade flat and curly, not stiff; plants rather delicate | Aristida platychaeta |
| Lemma usually more than 6.5 mm long; leaves with blade stiff and usually folded; robust, wiry plants
Back to 33 | 35 |
| 35 | Glumes subequal; lemma 6–8.5 mm long; awns 8–15 mm long | Aristida nitidula |
| Glumes unequal; lemma 8.5–12 mm long; awns 13–18 mm long
Back to 34 | Aristida strigosa |
