The varieties are difficult to distinguish as there appear to be a wide range of trichome types and degree of glaucous covering, the latter perhaps a result of different preserving and drying techniques.
Key to the Varieties of N. duidae
1. Lower surface of leaves cinereous-lepidote .......................................... var. duidae
1. Lower surface of leaves minutely punctulate-lepidote, glaucous, not cinereous var glabrior —SeeSteyermark, Holst et al. 1989
