1. Lemmas 1-3 awned, deeply 3 lobed; glumes much longer than florets (excluding awns) 2
Lemmas awnless or rarely aristulate, 3 toothed or shallowly 3 lobed; glumes much shorter than florets 22


Spikelets up to 8 mm long (excluding awns); lemmas membranous 3
Spikelets more than 8 mm long; lemmas hardened to some degree 5
3. Leaf blades pseudopetiolate T. cremnophila (WA)
Leaf blades not pseudopetiolate  4
4. Inflorescence c. 4 cm wide; central lemma awn c. 4 mm long T. bynoei (NT WA)
Plectrachne bynoei
Inflorescence c. 2 cm wide; central lemma awn to 20 mm long T. bunglensis (WA)
Plectrachne bunglensis
5. Lemma with a transverse line or thickening at base of lobes 6
Lemma without a transverse line or thickening at base of lobes 10
6. Body of lemma at least 4.5 mm long 7
Body of lemma up to 3 mm long 8
7. Body of lemma 4.5-5 mm long; culms to 80cm tall; inflorescence 10-14 cm long T. helmsii (SA WA QLD)
Plectrachne helmsii
Body of lemma 5-7 mm long; culms to 1.5m tall; inflorescence to 25 cm long T. acutispicula (WA)
Plectrachne caroliniana
8. Glume 15-20 mm long T. schinzii (NT SA WA QLD)
Plectrachne schinzii
Glumes up to 12 mm long 9
9. Glumes 4.5-6 mm long T. clayonii (WA QLD)
Triodia mollis, Plectrachne mollis
Glumes 7-12 mm long T. bitextura (NT WA QLD)
Plectrachne pungens, P. pungens var. callosum
10. Palea densely pubescent 11
Palea glabrous or lightly pubescent at base and ciliolate on keels 12
11. Spikelets 9-13 mm long T. rigidissima (WA)
Plectrachne rigidissima
Spikelets 15-18 mm long T. desertorum (WA)
Plectrachne desertorum
12. Glumes with long awns 13
Glumes awnless or with short awns 14
13. Lower glume 1-awned, upper with small lateral lobes T. bromoides (WA)
Plectrachne bromoides
Both glumes 3 awned, lateral awns c. 1/2 as long as median T. aristiglumis (NT)
Plectrachne aristiglumis
14. Body of lemma c. 4 mm long 15
Body of lemma 5-8 mm long 20
15. Lower culm internodes with woolly hairs 16
Lower culm internodes glabrous 17
16. Lemmas 1-awned, awns strongly curved or contorted T. contorta (NT)
Plectrachne contorta
Lemmas 3-awned, awns straight or slightly bent T. melvillei (NT SA WA)
Plectrachne melvillei
17. Lemmas 1 awned T. uniaristata (NT)
Plectrachne uniaristata
Lemmas 3 awned 18
18. Culms resinous T. salina (NT WA)
Culms non-resinous 19
19. Panicle 20-30 cm long; aerial roots and stolons absent T. prona (WA)
Panicle 7 -15 cm long; aerial roots and stolons present T. aeria (WA)
20. Lower leaf-sheaths and culm internodes densely covered with woolly hairs T. danthonioides (WA)
Plectrachne danthonioides
Lower leaf-sheaths and culm internodes not covered with woolly hairs 21
21. Glume 11-16 mm long T. longipalea (WA)
Plectrachne drummondii
Glumes 6-8 mm long T. dielsii (WA)
Plectrachne dielsii
22. Leaf blades flat or incurved-tubular T. procera (NT)
Leaf blades terete due to conduplicate folding 23
23. Leaf sheaths resinous; culms laterally flattened 24
Leaf sheaths not resinous nor culms laterally flattened 37
24. Spikelets up to 6 mm long 25
Spikelets more than 6 mm long 29
25. Lemma apex slightly lobed or entire 26
Lemma with equal lobes divided to middle 27
26. Lemma slightly lobed; lemma 9-nerved T. cunninghamii (WA)
Lemma entire; lemma 3-nerved T. biflora (WA)
27. Lemma with 3 small pointed lobes, median being twice as long as laterals T. stenostachya (NT WA QLD)
Lemma with 3 minute teeth 28
28. Spikelets 4-5 mm long; glumes acute; palea not winged T. microstachya (NT WA QLD)
Spikelets 6-8 mm long; glumes emarginate or 2 lobed; palea winged T. radonensis (NT)
29. Palea shorter than total length of lemma (body and lobes) 30
Palea almost as long as total length of lemma 34
30. Lemma lobes 1/3-1/2 lemma length T. triaristata (NT QLD)
Lemma lobes 1/8-1/3 lemma length 31
31. Spikelets 4-8 mm long, 4-7-flowered; lemma lobes less than 1 mm long T. burbidgeana WA)
Spikelets 7-14 mm long, 5-10-flowered; lemma lobes more than 1 mm long 32
32. Spikelets 8-9 mm long T. pungens (NT SA WA QLD)
Spikelets more than 9 mm long 33
33. Lemma 3-nerved; spikelets 1.5-2 mm wide T. latzii (NT)
Lemma 9-nerved; spikelets 3-5 mm wide T. epactia (NT WA)
34. Lemma ±as wide as long T. marginata (NSW QLD)
Lemma longer than wide 35
35. Glumes 5-9-nerved; lemma lobes half as long as the lemma T. longiloba (NT WA)
Glumes 3-nerved; lemma lobes less than half as long as the lemma 36
36. Spikelets narrowly eliptic; glumes mucronate T. hubbardii (NT)
Spikelets ovate; glumes not mucronate T. mitchellii (NSW NT QLD)
T. hostilis
37. Inflorescence a simple or compound raceme or spike 38
Inflorescence an open panicle 50
38. Inflorescence a simple raceme or spike 39
Inflorescence spicate or racemose on lateral branches 41



Lemma 3 lobed apically; inflorescence a simple raceme T. plurinervata (WA)
Lemma not lobed; inflorescence a simple spike 40
Basal lemma 5-8 mm longwith midrib hirsute in lower half T. spicata (NT WA)
Basal lemma 4.5-5 mm long with midrib glabrous T. fissura (WA)
41. Lemma with 3 groups of 3 nerves; leaf sheaths hairy or tomentose at base 42
Lemma with 3 strong nerves; leaf sheaths glabrous 44
42. Plants with scattered droplets of secretion T. roscida (NT WA)
Plants without secretion 43
43. Spikelets 17-25 mm long T. integra (NT)
Spikelets 10-14 mm long T. molesta (QLD)
44. Palea not winged on nerves 45
Palea winged on nerves 47
45. Lemma hairy on back and margins T. secunda (WA)
Lemma glabrous or with a few basal hairs 46
46. Spikelets at least 6 mm long T. angusta (WA)
Spikelets 2-3 mm long T. pascoeana (WA)
47. Lemma membranous T. fitzgeraldii (WA)
Lemma leathery 48
48. Spikelets 4.5-6 mm long T. racemigera (NT WA)
Spikelets more than 6 mm long 49
49. Glumes 1-nerved; lemma minutely toothed T. longiceps (NT SA WA QLD)
Glumes 3-nerved; lemma 3 lobed T. triticoides (WA)
50. Lemma lobes as long as or longer than base 51
Lemma lobes shorter than base 52
51. Lateral lemma lobes acuminate and hairy T. lanigera (WA)
Lateral lemma lobes obtuse and glabrous T. basedowii (NSW NT SA WA QLD)



Inflorescence very open; glumes shortly awned 53
Inflorescence loosely narrow or small; glumes not shortly awned 54
Spikelets 3.5-4.5 mm long; lemma 9-nerved T. barbata (WA)
  Spikelets 6-7 mm long; lemma 3-nerved T. plectrachnoides (NT)
Spikelets 9-13 mm long; lemma 5-nerved T. aurita (NT)
54. Lemma 3 lobed or 3 toothed apically; palea nerves winged 55
Lemma notched or truncate apically; with a mucro or short awn in notch; palea nerves not winged 62
55. Leaf sheath orifice and base of blade with erect or spreading hairs 56
Leaf sheath orifice and base of blade with woolly tangled or short hairs 58
56. Median lobe longer than laterals T. inaequiloba (WA)
Median lobe equal in length to laterals 57
57. Lemmas 3 toothed apically T. intermedia (NT WA)
Lemmas 3 lobed to 1/4-1/3 of lemma length T. wiseana (NT WA)
58. Leaf sheath orifice with very short hairs T. longiceps (NT SA WA QLD)
Leaf sheath orifice with woolly, tangled hairs 59
59. Lemma with a fringe of hairs between lateral nerve group and margin T. brizoides (NT WA QLD)
T. burkensis, T. clelandii
Lemma without a marginal fringe of hairs 60
60. Lemma 3 toothed T. concinna (WA)
Lemma 3 lobed 61
61. Spikelets ovate; palea wings distinct T. molesta (QLD)
Spikelets narrowly elliptic; palea wings very narrow T. inutilis (NT WA)
62. Glumes ±equal to spikelet length T. irritans (NT SA WA)
Glumes ± half spikelet length 63
63. Leaf sheath and orifice with woolly hairs 64
Leaf sheath and orifice glabrous, scabrid or with short, soft hairs 65
64. Glumes glabrous, 11-12 mm long; lemma 9-10 mm long T. tomentosa (WA)
Glumes hairy, 7-10 mm long; lemma 6-8 mm long T. lanata (SA)
65. Spikelets 8-12-flowered T. compacta (SA)
Spikelets 4-8-flowered 66
66. Lemma apex broadly truncate, with a distinct apical mucro T. scariosa (NSW VIC SA WA QLD)
T. truncata
Lemma apex emarginate, with or without a slender mucro between lemma lobes 67
67. Spikelets 6-8mm long; lemma hairs woolly and interwoven T. vella (QLD)
Spikelets 8-10mm long; lemma hairs not woolly, and straight 68
68. Glumes and lemmas cartilaginous; florets tightly imbricate T. bunicola (SA VIC)
Glumes and lemmas scarious; florets loosely imbricate at maturity T. scariosa (NSW VIC SA WA QLD)
T. truncata

Key to Triodia derived from Lazarides 1997, Barrett et al 2005, Barrett & Barrett 2011

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith