"Iwa-ume" (Diapensia lapponica var. obovata) belongs to the Diapensiaceae family. It is an evergreen shrub that is distributed from Chubu district of Honshu to Hokkaido, and Northeast Asia. This tree grows on the rocky area of the alpine zone, and its height is 2-5 cm. It creates a dense mat-like community. The leaves are small obovate, entire, and alternate each other closely. The pale greenish yellowish flowers come in July to August. The corolla is 5 split apart, short bell-shaped with a diameter of about 1 cm, and often reddish when it is overgrown.