Since 1973, Zhu Zhao Hua and other scientists of the Paulownia Research Group in the Chinese Academy of Forestry, have done a systematic survey of Paulownia resources and have accumulated many technical details which provide further information for the taxonomic revision of the genus and correct identification of species. However, the relationship of this genus is still argued. Some contend that the genus should be in the Bignoniaceae while others believe that Paulownia should be in a separate family, but most favour placing it in the Scrophulariaceae. Following the opinions of most taxonomists we consider Paulownia as a genus of the family Scrophulariaceae. Often, all the parts, except the old branches, are covered with mucilaginous glandular hairs, multiplenoded thick hairs, and dendritic or stellate hairs.
Most Paulownia species have pseudo-dichotomous branches whose terminal buds dry up after winter.
P. fortunei is exceptional in that the terminal buds sometimes grow into new branches. In young trees representing juvenile phase the leaves are large with long petioles, serrate margin, opposite and sometimes whorled in arrangement. The inflorescence is a cyme of two to five flowers may be pedunculate or subsessile. They are produced in the axils of diminutive or smaller leaves in summer and autumn. Flowers are pedicellate and articulate at the apical end.