This species is characterized by its rather robust habit, well developed triangular stipules that are divided into several triangular segments, medium-sized petiolate leaves, shortly pedunculate inflorescences with the flowers subsesssile in one to several small heads, its medium-sized fruits, and its remarkably long corollas. The corolla tubes are about 45-80 mm long.

Rudgea graciliflora is similar to Rudgea obtusa, Rudgea lanceifolia, and Rudgea klugii. Prolonged corolla tubes are also found in Rudgea longiflora and species similar to it. Zappi (2006) circumscribed Rudgea graciliflora to include plants from the northern and western Amazon basin, in Ecuador and Peru, that have sometimes been separated as Rudgea klugii. However the plants described as Rudgea klugii differ from Rudgea graciliflora of the eastern Amazon basin in their longer calyx limbs (2--3.5 mm) and corolla lobes (12--15 mm) along with their generally brown drying color, vs. shorter calyx limbs (ca. 0.5 mm) and corolla lobes (6--8 mm) and generally green drying color in Rudgea graciliflora. Zappi (2004) did recognized Rudgea klugii as distinct species apparently distinct from Rudgea graciliflora, and it is provisionally separated on this web page.