Cryptocoryne erwinii superficially resembles C. lingua in the leaves, but the leaf blade is more horizontally oriented, with the abaxial surface distinctly lighter than the adaxial one. The 6–9 cm long spathe is exceptional and differs from all other Cryptocoryne species in being white, with the distal part of the limb subulate and purple inside, first bent backward to upright, later bending forward over the white, widely expanded, funnel-shaped entrance, which lacks a collar. Its chromosome number of 2n = 26 has hitherto only been reported for the recently described C. aura.