Poisonous silence: the dumb cane
Any sap from the dumb cane plant that gets into a human mouth will make the tongue swell, causing speechlessness in adults and sometimes killing children. This effect was used by slave-owners to torture unruly slaves working in Caribbean sugar plantations.

The dumb cane growing at The Living Rainforest
Despite its violent history and the dangerous chemicals found in its leaves and stems, the dumb cane is a very popular houseplant.