Isodon japonicus

Isodon japonicus (synonyms Rabdosia japonica, Plectranthus japonicus), known in Japan as hikiokoshi, is a perennial herb or subshrub in the mint family (Lamiaceae) native to East Asia, including Japan, Korea, and China. It develops erect, square (four-angled) stems usually 50–150 cm tall arising from a woody rootstock, often branched in the upper part and finely hairy. The opposite leaves are ovate to broadly egg-shaped with serrate margins, a pointed tip, and a narrowed, winged base, and are intensely bitter to the taste. Small two-lipped flowers, pale violet to bluish, are borne in many-flowered, loosely branched panicled cymes in late summer and autumn; each flower has the characteristic mint corolla with the stamens and style enclosed or slightly exserted. The plant produces small, smooth nutlets. It grows in mountain woodland margins, thickets, grassy slopes, and clearings in temperate East Asia.