This species is characterized by medium-sized stiff-textured leaves, subsessile to shortly pedicellate 4-merous flowers, a dentate calyx limb ca. 0.5-1 mm long, and green to whitened or yellowish green corollas with the slender tube 12-19 mm long. The corolla tubes are weakly funnelform, and the lobes are somewhat well developed and and form an subglobose portion on the top of the bud. The inflorescence axes are glabrous in most specimens seen, but on occasional plants from throughout the range of the species are puberulous to pilosulous. Fedinandusa chlorantha is quite commonly collected in the western Amazon basin. It is similar to Ferdinandusa uaupensis, and these have been extensively confused as discussed below, and these are separately partially differently here than by some authors. Sterile material from the western Amazon basin is here included in Ferdinandusa chlorantha because the leaves match only this confirmed species in this region, but those identifications should be considered provisional. 

Ferdinandusa uaupensis is much less common, and has 5-merous corollas with the lobes relatively shorter and the tube a bit more slender and cyoindrical in bud, and generally longer calyx lobes.Ferdinandusa uaupensis also often has leaves with the secondary veins more pronounced and the surface even sometimes weakly bullate, but the separation of species of Ferdinandusa based on vegetative characters is problematic for all the species except Ferdinandusa elliptica. Anunciação reported Ferdinandusa uaupuensis only from the Rio Negro basin, but she annotated various MO specimens from the Ecuador and Peru with this name, but did not cite them in her treatment; hese all have four-merous flowers, and are here included in Ferdinandusa chlorantha.