This species is characterized by medium-sized to somewhat robust, elliptic-oblong to elliptic-ovate leaves, pedicellate 5(6)-merous flowers, white to pale green or yellowish green corollas with the tube 18-25 mm long, and rather short cylindrical capsules. The leaves vary in size and form, from rather short and stiff-textured with truncate to cordate bases, to longer and thin-textured with cuneate bases. Both forms can be found on the same plant (e.g., McPherson 11153, MO), and the shorter leaves seem to be more often associated with the inflorescence while the vegetative leaves are frequently much more robust. (e.g., Rueda et al. 10048). Only one species can be found in this group based on flower and fruit characters. One specimen from western Colombia with relatively small stiff-textured leaves was separated by Anunciação (2004) as Fernandusa lorentensis, but that specimen matches other specimens of Ferdinandusa panamensis from Panama and Colombia and is here included in this latter species.
This species has been confused at times with a plant treated by Weddell as Gomphosia goudotiana, which was a name based on Cinchona dissimiliflora and thus typified by the original material of that other name. The original name, Cinchona dissimiliflora, was based on Mutis material of Macrocnemum roseum and is a synonym of that. Weddell's Gomphosia name was a superfluous illegitmate replacement name for Cinchona dissimilis, so it is also a synonym of Macrocnemum roseum. However, Weddell also cited in his protologue a Goudot collection from central Colombia, which is a Ferdinandusa. Several later authors have assumed that Weddell's name was typified by the Goudot collection, and noted that this specimen is a species of Ferdinandusa and have then inaccurately treated Weddell's species in this other genus, variously as Ferdinandusa dissimiliflora (Standley, 1930; Delprete & Cortés-Ballén, 2016) or with the unpublished name "Ferdinandea goudotiana " (Anunciação, 2004).