Earlier authors placed a number of "Sedum" species outside of these clades, such as "S. spurium", "S. stellatum" and "S. kamtschaticum" (Telephium clade), that has been segregated into "Phedimus" (tribe Umbiliceae). Given the substantial taxonomic challenges presented by this highly polyphyletic genus, a number of radical solutions have been proposed for what is described as the "Sedum problem", all of which would require a substantial number of new combinations within Sempervivoideae. Nikulin and colleagues (2016) have recommended that, given the monophyly of Aeonieae and Semperviveae, species of "Sedum" outside of the tribe Sedeae (all in subgenus "Gormania") be removed from the genus and reallocated. However this does not resolve the problem of other genera embedded within "Sedum", in Sedeae. In the largest published phylogenetic study (2020), the authors propose placing all taxa within Sedeae in genus "Sedum", and transferring all other Sedum species in the remaining Sempervivoideae clades to other genera. This expanded "Sedum" "s.l." would comprise about 755 species.