The four known species of Philibertia that lack a corona, with a stylar head that rises above the anthers, and with flowers over 1.5 cm long can be differentiated using the following key.

1. Corolla tube internally pubescent .............................................................................................................................. 2

1. Corolla tube internally glabrous ................................................................................................................................. 3

2(1). Corolla lobes held more or less erect; flowers nodding ....................................................................... P. longistyla

2. Corolla lobes spreading; flowers not nodding ............................................................................................. P. latiflora

3(1). Corolla tube 25-30 mm long; stylar head appendage included within the corolla tube; corpusculum at least 2.5 mm long ................................................................................................................................................................. P. speciosa

3. Corolla tube less than 15 mm long; stylar head appendage generally exserted from the mouth of the corolla; corpusculum 1.4-2 mm long .............................................................................................................................. P. woodii