While plants may seem innocuous, some of them are surprisingly lethal to humans who may come into contact with them. Because plants cannot run away from predators such as animals, they can develop toxicity as a defence to protect them selves. Often the shoots of the pants are very high in concentrated with poison and can be more harmful if consumed. The toxicity of a plant usually increases with rising carbon dioxide and plants are more toxic during a drought.
There are about a 1000 species of plants in Australia alone that are known to be toxic to both animals and humans. With plenty more with the ability to cause skin and eye irritation, rashes or discomfort.
About 10% of plants in Australia even make cyanide. Plants may vary from region to region, but no matter where you are you should know what to keep an eye out for.
However, it is very difficult to determine what plants may pose risks to humans due to a lack of information about the diverse range of effect many plant species have on humans. A lot of literature refers to plants poisonous to animals, however while it's something to go by this doesn’t necessarily mean that the same rules will apply to humans.
There are also many different variables that make identifying poisonous plants and their risks very difficult. There is a seasonal variation in plants, in terms of the content of the poisons in the different parts of plants. The leaves and flowers of these plants may also have different amounts of poison or toxins is a perfect example.
There are a few well-known toxic plant species that humans should avoid these include:
• Black bean trees
• Strychine tree
• Angel's trumpet
• Deadly nightshade
• Milky mangrove
• Nettle family