Key to the species of Trithecanthera

1Leaves alternate, opposite or scattered
1'Leaves verticillate in whorls of 4 or more
2Leaves mostly alternate, petiolate; inflorescence axis c. 55 mm long, bearing c. 20 flowers; corolla yellow
2'Leaves opposite, sessile or nearly so; inflorescence axis 140-190 mm long, bearing 40 or more flowers; corolla red
3Inflorescence axis 20-40 mm long
3'Inflorescence axis more than 200 mm long
4Leaves in whorls of c. 8; inflorescence axis lacking a sterile tip; flowers yellow
4'Leaves in whorls of 4; inflorescence axis with a sterile tip more than 150 mm long; flowers pink or red