stavesacre

noun

staves·​acre ˈstāv-ˌzā-kər 

1

: a Eurasian plant of the genus Delphinium (D. staphisagria) having purple flowers

2

: the ripe seeds of the stavesacre that contain delphinine, are violently emetic and carthartic, and have been used to kill head lice

called also staphisagria