S. spectabilis was long placed in Cassia, or in the non-monophyleticCathartocarpus assemblage, or separated - together with its relative Senna peralteana - in Pseudocassia. In addition, is has been variously treated under a range of taxa, some of which were also used for related plants:
Cassia amazonica <small>Ducke</small>
Cassia carnaval <small>Speg.</small>
Cassia edulis <small>Posada-Ar.</small>
Cassia excelsa <small>Schrad.</small> var. acutifolia <small>Hassl.</small>
Cassia excelsa <small>Kunth</small> is a synonym of Cassia fistula. See also below.
Cassia acutifolia <small>Delile</small> and Senna acutifolia <small>(Delile) Batka</small> are synonyms of Senna alexandrina <small>Mill.</small>
Cassia humboldtiana <small>DC.</small>
Cassia speciosa <small>Kunth</small>
Senna speciosa <small>Roxb.</small> is a synonym of Senna surattensis <small>(Burm. f.) H.S.Irwin & Barneby</small>. See also below.