[6] Containing 80 - 117 species, it includes both deciduous and evergreen types and is distributed in Japan, China and northeastern Asia.

[citation needed] Tsutsusi are characterised by the presence of terminal buds that contain both floral and vegetative shoots.

[5] The section has traditionally included two subsections,[5][7] classified on the basis of their leaves, young twigs and corolla.

[4] The results of molecular analyses reveal that morphological features such as flower colour, corolla size, or whether leaves are mono- or dimorphic, appear to not be very useful in sorting out the phylogenetic relationships within section Tsutsusi.

Temperate and subtropical regions of China and Japan, but also found occasionally in Korea, Thailand, Burma, Laos and India.