| 1. | Awns 4-6 cm long | *B. diandrus (NSW VIC TAS NT SA WA QLD) B. gussonii, B. rigidus |
| Awns up to 3 cm long or absent | 2 | |
| 2. | Awn arising from back of lemma 3/4 way from base | *B. alopecuros (NSW VIC TAS SA WA QLD) B. alopecuroides, B. lanceolatus |
| Awn arising at or near lemma apex | 3 | |
| 3. | Lemmas laterally compressed and sharply keeled | 4 |
| Lemmas not compressed, rounded on back | 7 | |
| 4. | Inflorescence ±compact with rigid branches | *B. brevis (NSW TAS) |
| Inflorescence ±loose with flexuous branches | 5 | |
| 5. | Glumes spreading, awned | *B. cebadilla (NSW VIC TAS) B. stamineus |
| Glumes nor spreading or awned | 6 | |
| 6. | Lemma awns less than 3 mm long or lemmas awnless; spikelets glabrous | *B. catharticus (NSW VIC TAS SA WA QLD) B. unioloides, B. wildenowii |
| Lemma awns 5-7mm long; spikelets pubescent | *B. lithobius (NSW VIC TAS) B. fonkii, B. cebadilla auct. |
|
| 7. | Lower glume 3-7-nerved; upper glume 5-9-nerved | 8 |
| Lower glume usually 1-nerved; upper glume 1-3-nerved | 11 | |
| 8. | Lower leaf-sheaths glabrous or weakly hairy | *B. secalinus (NSW) |
| Lower leaf-sheaths distinctly hairy | 9 | |
| 9. | Most pedicels longer than their spikelets; inflorescence ±lax | *B. racemosus (NSW VIC) |
| Most pedicels shorter than their spikelets; inflorescence ±dense | 10 | |
| 10. | Awns flattened at base | *B. hordeaceus subsp. molliformis (NSW QLD) B. molliformis |
| Awns terete at base | *B. hordeaceus subsp. hordeaceus (NSW VIC TAS SA WA QLD) B. mollis |
|
| 11. | Lemmas awnless or with short awns to 3 mm long | *B. inermis (NSW) |
| Lemmas awned with awns more than 4 mm long | 12 | |
| 12. | Inflorescence open and loose | 13 |
| Inflorescence contracted | 14 | |
| 13. | Awns straight | *B. sterilis (NSW VIC TAS WA) |
| Awns curving away from spikelet | B. arenarius (NSW VIC TAS SA WA QLD) B. japonicus |
|
| 14. | Inflorescence very dense; lemma teeth 2-4 mm long | *B. rubens (NSW VIC SA WA QLD) |
| Inflorescence moderately dense; lemma teeth 1-2 mm long |
15 | |
| 15. | Spikelets 2.5-3.5 cm long (including awns) | *B. tectorum (NSW VIC) B. tectorum var. hirsutus |
| Spikelets 3.5-6 cm long | *B. madritensis (NSW VIC TAS SA WA QLD) |
Key to Bromus derived from Wheeler, Jacobs and Norton 1990
Taxonomic name: