1. Primary branches of inflorescence not divided, bearing only terminal racemes 2
Primary branches of inflorescence divided, bearing terminal and lateral racemes 3

2. Spikelets awnless S. nitidum f. nitidum (QLD)
Spikelets awned S. nitidum f. aristatum (QLD)

S. serratum

3. Inflorescence axis much thicker than branches; grains large, exposed at maturity *S. bicolor (NSW VIC NT SA WA QLD)
Inflorescence axis slightly thicker than branches; grains small, enclosed by glumes at maturity 4

4. Rhizome present 5
Rhizome absent 6

5. Sessile spikelet 5-6.5 x 2-5mm *S. x almum (NSW NT WA QLD)
Sessile spikelet 4.5-6 x 1.8-2mm *S. halepense (NSW VIC SA WA QLD)

S. halepense forma muticum, S. miliaceum

6. Sessile spikelet breaking clean from apex of rachis internode *S. arundinaceum (QLD)

S. bicolor subsp. arundinaceum, S. verticilliflorum
Sessile spikelet breaking together with upper portion of rachis internode *S. x drummondii (NSW WA QLD)

S. bicolor subsp. drummondii, S. sudanense

Key to Sorghum derived from Garber 1950; Simon 1979; Lazarides et

al. 1991; Spangler

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