Dieffenbachia or dumb cane, Dieffenbachia spp.
A tropical South American plant well known for its ability to temporarily inflame vocal cords, leaving people unable to speak. Some species are believed to have been used as an arrow poison in combination with other plants. Most poisonings involve severe irritation of the mouth and throat, swelling of the tongue and face, and stomach problems. The sap is also irritating to the skin, and can cause light sensitivity and pain if it gets in the eyes.
Ficus tree and rubber tree, Ficus benjamina, F. elastica
These two indoor trees are closely related species in the mulberry family. The latex from these plants can provoke severe allergic reactions. One case history describes a woman who developed anaphylactic shock and other frightening symptoms that disappeared promptly after her ficus tree was removed from her home.
Pencil cactus or milkbush, Euphorbia tirucalli
This African plant is actually not a cactus, but it gets its name from the long, skinny stems that resemble a succulent. Pencil cactus has become popular in modern interior design for its striking, architectural shape. But like other euphorbia, it produces a corrosive sap that causes severe rashes and eye irritation. It requires some pruning to keep it down to a reasonable size indoors, and gardeners are often surprised that a single pruning session can bring on such a painful reaction.
Jerusalem cherry or Christmas cherry, Solanum pseudocapsicum
Often sold as an ornamental pepper plant, it is actually more closely related to deadly nightshade. All parts of the plant contain an alkaloid that can bring on weakness, drowsiness, nausea and vomiting, and heart problems.
Reprinted with permission from Wicked Plants: A Book of Botanical Atrocities. Copyright 2009 by Algonquin Books of Chapel Hill