Dieffenbachia

Their sap is thick and contains huge quantities of needle-shaped calcium oxalate crystals. When chewed or even just touched, the sap causes swelling and a burning sensation, and a temporary inability to speak. This is why it is called dumb cane. It can cause death if the swelling blocks the airway.

Slaves were sometimes punished by having dieffenbachia put into their mouths.

If you have this plant in your house or yard, wash your hands after handling it.