The species was first formally described in 1939 by Earl Edward Sherff, based on specimens collected from Waipio Valley in Kohala, Hawaii in 1938.

[2] Sherff named the species after Auckland War Memorial Museum botanist Lucy Cranwell, who was one of the three people who collected the specimen.

[3][4] Phylogenetic analysis of Hawaiian mints has shown that S. cranwelliae is closelyt related to S. calaminthoides, S. macrantha, S. sessilis and S.

[5][6] Stenogyne cranwelliae has elongated stems which measure approximately 1.5–2.5 mm (0.059–0.098 in) in thickness.

[4] The species is endemic to Hawaii, uncommonly found in wet forested areas.