Limonia acidissima is the only species within the monotypic genus Limonia. It belongs in the monotypic genus Nasalis. The species is monotypic with no living subspecies. It is the sole species in the monotypic genus Cnicus. It is the sole species in the monotypic genus Watasenia. It is the only species in the monotypic genus Lablab. It is the only species in the monotypic genus Zootoca. It is the only species in the monotypic genus Olneya. It is the only species in the monotypic genus Ixoreus. It is monotypic within the genus Trichobatrachus. The other genera are largely monotypic or oligotypic. He placed it in the monotypic subgenus "Anourosperma". This resulted in a proliferation of monotypic genera. The saguaro is the only species in the monotypic genus "Carnegiea". It is the sole species in the monotypic genus, Ricinus, and subtribe, Ricininae.