The area of Tashirobaru, also called "Oku-Unzen (Deep Unzen)", is the grasslands located at an altitude of 600 meters. Cattle and hourses have been pastured here since the Edo period (1603-1867). If not tended, Japanese grasslands would eventually transition into forests. Since cattle and hourses do not eat Yama-tsutsuji (mountain azalea), they have been excellent gardeners and maintained the grasslands and the colony of Yama-tsutsuji and Miyama-kirishima (Kyushu azalea).