“Double-flowered” describes varieties of flowers with extra petals, often containing flowers within flowers. Yaezakura in Japanese means double-flowered cherry blossoms and Prunus ‘Kanzan’ is a representative cultivar of the Yaezakura cherry blossoms. Kazan is a double flower cultivar with with 20 to 50 petals.
Double-flowered: https://en.wikipedia.org/wiki/Double-flowered; Prunus ‘Kanzan’: https://en.wikipedia.org/wiki/Prunus_%27Kanzan%27; https://www.southern.edu/arboretum/plant/view?id=514#slide-id-3804; https://www.nps.gov/subjects/cherryblossom/types-of-trees.htm
Yaezakura cherry blossoms, Arakura Sengen Park, Fujiyoshida-shi, Yamanashi, 4/24/2026