This species is characterized by its rather robust oblanceolate leaves, lax racemiform to pyramidal inflorescences with yellowish green pink axes and numerous medium-sized flowers, tubular green to pink corollas with the anthers partially exserted, and medium-sized obovoid capsules. The inflorescences were described as "secundiflorous" by Delprete (1999), meaning that the axes are held horizontally and the flowers are all pendulous. The corollas are bright greenish yellow or green, and often flushed with pink on the basal portions. The corollas are angled to acute bud, and at anthesis have cylindrical tubes 15-25 mm long and well developed lobes 9-13 mm long. The length of the corolla lobes is not on evident on many buds, where they appear to be quite short but then their split apparently developed basipetally as the bud matures. The fruits on the infructescences are less evidently secund.

Rustia schunkeana is similar to Rustia rubra, Rustia viridiflora, and Rustia thibuadioides.