Generally, poisoning is unlikely unless a plant is highly toxic or large quantities are ingested (for example, if the leaves or other components are concentrated into a paste or brewed into a tea)
Highly toxic and potentially fatal plants include castor beans and jequirity beans, poison hemlock and water hemlock, and oleander and foxglove
Only a few plant poisons have specific antidotes, so doctors usually just treat people's symptoms.
(See also Overview of Poisoning Overview of Poisoning Poisoning is the harmful effect that occurs when a toxic substance is swallowed, is inhaled, or comes in contact with the skin, eyes, or mucous membranes, such as those of the mouth or nose... read more .)
Many other plants cause less serious toxic effects (see table Moderately Poisonous Plants Moderately Poisonous Plants 
).
Castor and jequirity beans
Castor beans contain ricin, an extremely potent poison. Ricin has been used in assassination attempts and as a mass-casualty weapon Toxins as Weapons "Toxin" is often loosely used to refer to any poison but technically refers only to a poisonous chemical produced by an organism (although some toxins can now also be produced synthetically)... read more . Castor bean seeds have a very tough shell so the bean must be chewed to release the poison.
Jequirity beans contain abrin, a related and even more potent toxin than ricin. The beans can be fatal if swallowed. Children can die after chewing only one bean.
Poisoning from castor beans or jequirity beans may cause severe vomiting and diarrhea (often bloody) after a delayed period. People later become delirious and have seizures. They may become comatose and die.
Doctors sometimes try to flush the beans out of the stomach and intestines before they are absorbed. There is no antidote but doctors give people fluids by vein (intravenous) and other care to treat their symptoms.
Hemlock
Hemlock poisoning can cause symptoms within 15 minutes. People develop a dry mouth and later a rapid heartbeat, tremors, sweating, seizures, and muscle weakness. Water hemlock may cause vomiting and diarrhea, delirium, seizures, and coma. There is no antidote but doctors give people care to treat their symptoms.
Oleander, foxglove, and lily of the valley
Oleander, foxglove, and lily of the valley contain a substance very similar to the heart drug digoxin. These plants can cause vomiting and diarrhea, confusion, irregular heartbeat, and high levels of potassium in the bloodstream (hyperkalemia Hyperkalemia (High Level of Potassium in the Blood) In hyperkalemia, the level of potassium in blood is too high. A high potassium level has many causes, including kidney disorders, drugs that affect kidney function, and consumption of too much... read more ). Doctors sometimes treat people with DIGIFab, a drug used to treat digoxin overdose.
More Information
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
American Association of Poison Control Centers: Represents the US-based poison centers that provide 24/7 free, confidential services through the Poison Help Line (1-800-222-1222)
