Top 5 Poisonous Plants To Watch Out For

Some plants have developed compounds in their structure that act as defence mechanisms from herbivorous animals. Some of these substances have the ability to cause significant harm to humans if consumed or simply even touched. Here is a small selection of the poisonous plants and deadly varieties you should look out for.


From the same family as carrot and fennel this small umbrella shaped plant grows throughout North America and Europe. Its small green and white flowers grow from a highly toxic thick main stem that grows up to 7 feet tall. The flowers each have five petals and 5 stamens; this gives it its distinctive umbrella formation. The plant is found in wetland, typically pastures or along streams and was used by Native Americans to poison the tips of their arrows whilst hunting. It was also used, soaked in guaze, along with opium as a surgical anaesthetic.

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If the root is ingested it is so quickly toxic that an animal is unlikely to be saved. In humans seizures occur along with tachypnoea and tachycardia (rapid pulse and breathing) and must be halted with immediate administration of barbiturates (anticonvulsants). The metabolic acidosis caused may require treatment in an intensive care unit with artificial ventilation and haemodialysis.

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This intensely sweet bushy herb gets its name from a time venetian women would drop the toxic alkaloid juices from the ripe berry into their eyes in order to dilate their pupils, making them appear more attractive. A member of the Solanaceae family, its relatives include eggplant, potatoes and tomatoes and whilst it is native to Europe, North Africa and parts of Asia it has been introduced artificially to Canada and the United States. The atropine, hyocynamine and scopolamide are found in all parts of the plant with the highest concentrations being in the fruit and leaves.

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Ingestion causes an anti-cholinergic syndrome by blocking the muscarinic receptors in the central nervous system, a similar action to Parkinson’s medication. Signs and symptoms depend on the volume of toxin consumed and begin with dilated pupils, raised heart rate, flushed skin and progress to hallucinations, ataxia and seizures. Poisoning will not always present in the same way and it is important to recognise symptoms in children who may be attracted to the enticing berry with a high index of suspicion with slurred, meaningless speech and extreme tiredness or decreased conscious level.

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Treatment should include IV fluids to prevent muscle cell death and benzodiazepines to prevent seizures. Activated charcoal & bowel irrigation is useful when large amounts have been ingested and physostigmine can be used in severe cases.


From the same family as the harmless buttercup, the poisonous roots of this plant are absorbed through the skin causing numbness and tingling, which rapidly spreads to the rest of the body. Found in the moisture-retentive soils of the Northern Hemisphere the cowled hood of this plant is so distinctive and sinister it is easily distinguished from other species. Keen gardeners regularly grow the plant purposefully as an attractive garden border throughout all seasons with different varieties flowering throughout spring, summer and autumn. Alkaloids such as aconite have developed as a defence mechanism to insects and animals attracted to the beautiful purple and white flowers. The unpleasant taste make poisoning of humans unlikely but small amounts are capable of causing diarrhoea and vomiting.

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Ancient tribes used the toxins to kill wolves and leopards giving the variety the popular nickname wolf’s bane. Gardeners or florists working with the plant should ensure they adhere to strict hygiene regimes, wearing gloves and vigorously washing their hands after handling the plant.

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The Spanish call it the little apple of death, and for good reason. Merely a touch to your skin can leave you scalded and even the diluted sap falling with rainwater could give you a nasty rash. Growing throughout South America, through the Caribbean to the everglades of southern Florida this plant causes severe dehydration and death to anyone who contacts it. Don’t try to burn it down it an attempt to rid yourself of this devil, the smoke will burn your lungs and partially blind you.

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The phorbol in the sap is known for tumour promoting it causes a painful burning sensation and ulceration of the oral, oesophageal and gastric mucosa, which may be fatal in extreme cases. In mild cases, the application of Benadryl cream has been known to resolves skin rashes, as have mild corticosteroids. Ingestion of the fruit can cause severe symptoms and in many case reports a tightening of the throat and burning sensation are characteristic. Milk will ease the pain and oral steroids will reduce the inflammatory effect. This deadly tree does have its uses; it helps prevent beach erosion and acts as a windbreak amongst mangroves.


Found in temperate regions around the world particularly southeast Asia and India, these bright red seeds contain abrin toxin which can be lethal to humans. Luckily, the toxin is found within a hard shell which is undigestible by the human GI tract, however, if the shell is broken or well chewed the presence of abrin can cause death within 72hours. Poisoning is much more likely after ingestion of the immature seed in fall because immature plants have softer shells and the toxin is more easily absorbed in the GI tract leading to nausea, vomiting, diarrhoea and dehydration. Symptoms are often delayed in onset so gastric lavage or activated charcoal can be used as remedies.

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The plant itself is weedy and invasive, growing among trees, shrubs and hedges aggressively sucking nutrients from the soil. The black and red beans have been used in aborigine jewellery and used to ward off evil spirits.

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Do you know of any more deadly plants? Please comment below.

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Some plants have developed compounds in their structure that act as defence mechanisms from herbivorous animals. Some of these substances have the ability to...
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