キク科シオン属の多年草で、学名は Aster ageratoides var. ageratoides (syn. Aster leiophyllus var. leiophyllus)。英名はありません。
The "Shiro-yomena" (Aster ageratoides var. ageratoides) belongs to Asteraceae (the Aster family). It is a perennial herb that is distributed from Honshu to Shikoku and Kyushu, as well as Taiwan and the Korean Peninsula. This herb grows in mountain forest edges and roadsides, and can reach 30-100 cm in height. The leaves are oblong-lanceolate with short petioles. The surface of leaf is glossy and the abaxial side can be found prominent three veins. The white flower-heads bloom in corymbs-like clusters at the terminal branched stems from August to November. It resembles to "Inaka-giku" (Aster semiamplexicaulis), though it is defined by narrower ray flowers, dark green tubular bracts and flaccid plant body. In Taiwanese Chinese, it is called "山白蘭".