Answer:

ratsbane

AnswerCrossword Clue
RATSBANERattlesnake plantain.
RATSBANEChervil.
RATSBANETropical plant.
RATSBANEPoisonous plant
RATSBANEPoison also called white arsenic
RATSBANERodent-killing poison, old-style
RATSBANERodent pesticide