Strychnine tree (Strychnos nux vomica). This tree grows in southern Asia and Australia. Its dried, ripe seeds are the source of the poison strychnine. In the past, strychnine has been used as an antiseptic, circulatory and nervous system stimulant, and as a stomach tonic. However, its use is now limited to being a pest control agent, particularly to eliminate unwanted bird populations.