The world’s most poisonous plants (2024)

This beautiful shrub is native to Europe, North Africa, and West Asia. It is one of the best-known poisonous plants from ancient Egypt to the Middle Ages up until now. It is the ancient Egyptians they were responsible for promoting its use as a powerful narcotic.

The toxins responsible for its effects are atropine and scopolamine. In poorly administered doses it can affect the nervous system paralyzing even the nerve endings of involuntary muscles of the body such as the heart itself or blood vessels (which can lead to coma or death). Low doses can cause delusions and hallucinations. High doses of 10 to 20 berries are more than enough to kill a person.

Ricin or the infernal fig tree is a bush native to Africa with a thick, woody stem, whose leaves may be red or dark purple (hence its common name) and is usually covered with a white powder, ricin, which is highly toxic. Contact with this substance causes nausea, abdominal cramps, vomiting, internal bleeding and kidney failure, resulting in death 10 days after contact. Ricin interferes with human cellular metabolism; by blocking the chemical process that sustains life, cells die and organs begin to fail little by little until death is provoked. A lethal dose for an adult would represent five castor beans; for a child, only one.

Castor oil is extracted from its seeds.

Also known as matalobos or devil's helmet, this herbaceous plant originates from mountainous areas of the northern hemisphere of the planet. It is a very poisonous plant (considered the most toxic in Europe) because it contains aconitin, one of the most active and toxic alkaloids that, after a slight contact, can slow the heart to death and just 1mg of this plant is enough to kill an adult of 80kgs. The symptoms that occur after touching or ingesting aconite are burns in the mouth, salivation, vomiting, diarrhoea, heart problems, coma and, in some cases, death.

It grows in humid and cool environments (river banks, streams and on the edges of roads and fields); it is native to Europe and North Africa. This invasive species that can grow up to 2 meters high, contains all toxic substances such as cicutin that inhibits the functioning of the central nervous system producing the so-called "cicutism" (cyanosis, midriasis, convulsions and coma) that begins with vertigo, headaches, lower body temperature and reduction of muscle strength ending in paralysis. In order to kill a human being, only a few grams of its green fruits are necessary. The most famous historical figure who died after condemning him in a trial to drink a glass of hemlock, was the philosopher Socrates in 399 BC.

The oleander, also known as laurel of flower or trinitaria, is a shrub plant (of Mediterranean origin and therefore, resistant to droughts) with intensely green leaves and whose leaves, flowers, stems, branches and seeds are all highly poisonous, hence it is also known as "the most poisonous plant in the world". It takes first place because of its potent poison that contains several toxins (such as oleandrin) that act on the heart. The mistaken intake of this plant causes nausea, vomiting, vertigo, bowel movements, excitement and depression, convulsions, arrhythmias, tachycardias and finally cardiac arrest.

A historical fact: during the Spanish War of Independence (1808), a platoon of Napoleon's soldiers stopped to roast meat using oleander stakes found around the temporary camp. This caused 8 soldiers to die and the other four to be severely intoxicated.

With hallucinogenic properties, this poisonous plant grows naturally in warm areas around the world; present on riverbanks, stables, dunghills or garbage dumps, this versatile plant is able to adapt to all types of soil. The toxic substances that characterize it are the tropical alkaloids (atropine and scopolamine). In high doses, they can cause aggressive behaviour, coma and even death.

Their association with voodoo and witchcraft comes because shamans used to smoke its leaves along with tobacco to enter a trance. A small dose of four or five grams of leaves is enough to kill a child.

It was believed that its seeds calmed down symptoms of epilepsy, the possessed and also broke the spells that prevented a man from having sex with a certain woman. With a more stable scientific base, it is known to grow from February to June in areas close to a sea level of up to 1500 meters of altitude. In Spain it is present in different terrains. The particularity that makes it highly toxic and irritating is its aristolochic acid, which at high doses can produce respiratory paralysis.

It’s one of the most popular houseplants, as it is attractive and easy to grow. The unknown problem with this plant is that it contains calcium oxalate crystals, which are toxic to humans and animals. The intake of philodendron causes dermatitis, swelling of the mouth and digestive tract in humans, but in cats and dogs, its effect can be more serious and cause spasms, convulsions, pain and swelling.

This particular plant inhabits in dry and shaded areas. Its scientific name, Chelidonium, means 'small swallow', as the flowering period coincides with the arrival of these birds. For this reason, it is also known as 'Herba de las golondrinas' or 'golondrinera'. It can cause narcosis, the paralysis of sensitive nerve endings, bradycardia and tetanus contractures. Its continuous administration is considered to be carcinogenic.

Although its exact origin is unknown, this plant is believed to come from Central Asia and China; and now it is widespread throughout the world. Its seeds have been used as a purgative in both human and veterinary medicine. Extreme caution must be exercised with the Tártago, as it is also an abortifacient plant (it can reject a pregnancy is one’s body).

The floripondo has spread throughout Latin America and Europe and has been used as hallucinogens since time immemorial. It’s a small tree with elongated flowers that fall between 18 and 23 centimetres long. It contains tropical alkaloids, such as scopolamine, which are used in Parkinson's drug formulations. An overdose of these compounds can lead to paralysis, psychosis, hallucinations and also death.

It is found in forest clearings, generally in southwestern Europe and northern Spain (especially from Leon to Asturias). Its sale to the public is restricted, although it is used in some medicines such as laxatives or topical anti-inflammatory drugs. The ingestion of Bryonia fruits, however, can cause gastrointestinal irritation, with vomiting, coleriform diarrhoea (symptoms similar to cholera), intestinal bleeding or nephritis (inflammation of the kidneys). In high doses this plant can cause death by cardio-respiratory collapse.

This herbaceous plant originates from Arab countries, but its extension allows us to find it in the rest of the continents of the world. Although it is used as a topical medication to cure ulcers, boils, burns, irritations, wounds, and inflammations, is extremely dangerous for cats, because for them their intake can be deadly. In fact, without immediate treatment, during the first hours after consumption, there is more than a 50% chance that the animal will not survive.

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