Chinese quince (Pseudocydonia sinensis) is a small tree and has smooth, serrated leaves and single flowers, while Japanese quince (Chaenomeles japonica or Chaenomeles speciosa) is a thorny shrub and has glossy leaves and often has thorny branches with clustered flowers. Both fruits are aromatic and must be cooked, but the Chinese quince fruit resembles a true quince more closely, while the smaller Japanese quince fruit has a stronger, more sour flavor.
Chinese quince (Pseudocydonia sinensis): https://en.wikipedia.org/wiki/Pseudocydonia; https://specialtyproduce.com/produce/Chinese_Quince_24437.php; https://plants.ces.ncsu.edu/plants/pseudocydonia-sinensis/
Chinese quince, CMIC Yatsugatake Medical Plant Garden, Kobuchisawa, Hokuto, Yamanashi, 11/13&11/2025
Japanese quince (Chaenomeles japonica): https://en.wikipedia.org/wiki/Chaenomeles_japonica
Japanese quince, CMIC Yatsugatake Medical Plant Garden, Kobuchisawa, Hokuto, Yamanashi, 11/13/2025
CMIC HOLDINGS Co., LTD. https://en.cmicgroup.com/?cl=navi, CMIC Yatsugatake Medical Plant Garden (In Japanese) https://yatsu-garden.sakura.ne.jp/index.html
FYI: Quince (Cydonia oblonga) https://en.wikipedia.org/wiki/Quince