Its distinctive features are the very glaucous, sessile, opposite leaves which are fused around the stem. The only other species with leaves fused around the stem are E. tenuiramis (some juvenile leaves only) and E. perinniana. The tips of the leaves of E. risdonii are pointed, whereas E. perinniana has blunt juvenile leaves. E. risdonii is very closely related to E. tenuiramis (in fact, these two species probably represent extreme forms of a continuum with E. tenuiramis developing adult leaves whereas E. risdonii remains in the juvenile form through its life. Intermediate forms exist).