It should also be pointed out that this might not be the only centre of variation. Some species can produce a series of variations during the process of range expansion because of adaptation to the complex site and environmental conditions. Thus, they form secondary centre of origin for some species. For instance, in Sheng Long Jia mountainous region, Hupeh Province, the variation of Paulownia tomentosa is quite complex. This might be considered as another centre for this species.
Similar situations exist in other mountain areas.
Distribution of various Paulownia species. Some of the morphological variations of the genus Paulownia are quite interesting. For example, the inflorescence development may prolong for almost one year. The development begins in late summer lasts through autumn, usually overwinters and finally blossoms in the following spring. The juvenile leaves both on seedlings and immature branchlets are large and occasionally exceed 1 m in length.