A tall, coarse plant (Inula helenium) native to central Asia, having rayed yellow flower heads. The roots are used medicinally.

土木香大型粗糙的植物(土木香旋覆花属)，原产于中亚，花黄色，头状花序呈辐射状向四周延伸，根入药。

youdao

Early forms of teeth whitening include using the herb elecampane (Inula helenium) to scrub the teeth and taking sage leaves and making a powder of them and salt.

BBC: Medieval teeth 'better than Baldrick's'