Top 10 Most Dangerous Plant Species Worldwide

1. Manchineel

Manchineel is named after the Spanish for 'little apple of death'. It's one of the most toxic plants known as the 'tree of death'. It mainly grows across Florida, Central America, and the Caribbean. This large canopy tree can reach up to 15 meters in height with gray bark, glossy green leaves, and small clusters of greenish flowers. Its fruit, resembling small green apples, is highly toxic. The tree's toxicity pervades all its parts. Inhaling sawdust or smoke from burning the tree can cause coughing and bronchitis. Simply touching its sap can cause severe skin irritation and blisters. Ingesting its fruit leads to mouth inflammation, severe digestive symptoms, and even death.

Manchineel is so hazardous that warning signs and a minimum 6-meter distance are required. No other plant replaces its top position in terms of toxicity records. However, some animal species seem immune to its dangers. For instance, the spiny-tailed iguana in Central and South America can eat manchineel fruit without harm, even living directly on the tree trunk.

2. Heracleum mantegazzianum

Heracleum mantegazzianum is a flowering plant in the carrot family, also known as giant hogweed. It is native to Central Asia but has now spread to many places across Europe, North America, Australia, and scattered elsewhere around the world. The stem is straight, hollow inside, and the leaves resemble papaya leaves, with numerous small hairs on the stem and leaf branches measuring 2-7 cm long. The small white flowers form clusters. Mature plants can grow from 2 to 5.5 meters tall.

Heracleum mantegazzianum is highly toxic, with all parts of the plant containing toxicity. Especially when combined with sunlight, it can cause swelling and painful blistering akin to severe burns on both humans and animals. Accidental contact can result in swelling, heat, and intense pain equivalent to second-degree burns. More severe cases may induce fever, rapid heartbeat, and rapid breathing. Eye contact can lead to blindness.

In case of injury due to contact with Heracleum mantegazzianum, the patient should be taken to a doctor or hospital for prompt treatment. If this plant is detected, caution should be exercised and direct contact avoided when eradicating it, as all parts of the plant, including the roots, stem, leaves, flowers, and fruits, contain toxicity.

Ricinus Communic, also known as castor oil plant, is one of the plants you should never taste. This plant originates from East Africa but is now widespread worldwide, cultivated for ornamental purposes due to its beautiful colors. The castor oil plant has a weak stem but can grow up to 10 meters tall, with alternate leaves that have long petioles and duck-foot-shaped leaf blades, and flowers arranged in clusters.

Castor oil plant possesses both toxicity and medicinal properties. After extraction, the oil from this plant is used as a laxative, to cleanse the bowels, and to induce abortion. However, its seeds contain a highly toxic substance, mainly Ricin. Ricin causes death by directly interfering with the cell metabolism to sustain life, hindering the production of essential proteins, leading to cell death. Ricin is most dangerous in its purified form and when injected into the body; just 3mg injected subcutaneously can cause death in humans.

In Vietnam, the castor oil plant mainly grows and thrives in the mountainous regions of the Northwest such as Hoa Binh, Vinh Phuc, Lao Cai, and Ha Giang. It is rarely seen in the southern provinces and lowland areas.

Aconitum Napellus, also known as monkshood, is one of the four precious medicinal herbs (ginseng, deer antler, cinnamon, monkshood). Monkshood is a perennial herb, reaching heights of 0.6-1.8 meters, with short hairs covering its entire body. The flowers are purple, sometimes with green or white clusters at the apex. It is also known as the 'queen of poisons'.

Aconitum Napellus contains the toxin Aconitine, which is dangerous for anyone who ingests or even touches it. Aconitine is a neurotoxin that can be absorbed through the skin and has the ability to induce irregular heart rhythms. All parts of the plant are poisonous, including the roots and leaves. Symptoms of monkshood poisoning include excessive salivation, vomiting, diarrhea, itching, abnormal blood pressure, and heart rhythm abnormalities leading to death.

Aconitum Napellus is a highly toxic medicinal herb that needs to be processed before use. The roots of the plant are harvested for medicine, with the small roots called monkshood and the larger roots called head armor. Monkshood has the effects of warming the yang, dispelling wind-cold, and promoting blood circulation. To avoid monkshood poisoning, you should consult a doctor before using herbal medicine for treatment.

Taxus Baccata, also known as the yew tree, originates from Europe and Northwestern Africa. The European yew is the only tree that can withstand darkness in Europe. Mature trees typically grow to heights of 18.3-21 meters.

The yew tree is highly toxic, containing the toxic compound taxine alkaloids, present in all parts except the outer husk of the seed. Its toxicity can lead to severe symptoms such as dizziness, dry mouth, dilated pupils, weakness, irregular heartbeat, and ultimately, death.

However, since the 10th century, extracts from the yew tree have been used as medicinal resources to treat diseases like measles or smallpox. Additionally, extracts such as Paclitaxol and Taxol are derived for slowing the growth of ovarian and lung cancers.

Atropa belladonna, also known as deadly nightshade, is a perennial plant that produces delicate purple flowers and beautiful shiny black berries. Similar to Jimsonweed, this is a dangerous plant, causing hallucinations, delirium, and ultimately leading to death.

Atropa belladonna contains toxins such as atropine and scopolamine in its stems, leaves, berries, and roots. Poisoning by this plant can result in paralysis of the muscular and nervous systems, dilation of blood vessels, heart irregularities, digestive system paralysis, blurred vision, and seizures.

However, Atropa belladonna also has some beneficial applications. Atropine, a medicine for cardiac patients, is derived from this plant. Atropa belladonna is closely related to many familiar plants such as potatoes, tomatoes, eggplants, peppers, and even tobacco. This means that every household has some potentially harmful components, and Atropa belladonna is one such member.

Jimsonweed, also known as devil's snare, is a perennial herbaceous plant with woody stems at the base, sharp-pointed leaves, and spiny fruits. Its stems are reddish-purple, and the leaves emit a foul odor. The flowers are white, with green calyxes and five teeth on top. The plant reaches a height of 0.9-1.2 meters. Its fruit is highly toxic, containing atropine and scopolamine, with even the flower petals and nectar being toxic. It induces terrifying symptoms in humans: dilated pupils, increased heart rate, delirium, hallucinations, and even seizures.

According to traditional Chinese medicine, Jimsonweed has the effects of relieving coughs, preventing asthma, anti-convulsion, analgesia, and treating low back pain. Moreover, it is also used to support the treatment of abdominal pain, motion sickness, Parkinson's disease, whooping cough, bronchial asthma, and excessive sweating.

Jimsonweed is closely associated with the dark arts, witchcraft, and sorcery due to its hallucinogenic properties. For everyone else, it's a plant to stay away from.

In the world of poisons, Strychnos nux-vomica is also known as strychnine tree, recognized as a 'star,' it is a woody plant, originating from Southeast Asia, with medium-sized wood, can grow up to 25 meters tall, growing in sparsely populated environments up to an altitude of 1,200 meters. Its leaves are egg-shaped, measuring 5 x 9 cm. In Vietnam, the tree is also known as Củ Chi, Cổ Chi, Hoàng Đàn, or Võ Doản, etc.

Strychnine tree carries high toxicity, including strychnine and brucine. The seeds, flowers, and even the bark of the tree contain toxins. They cause horrific poisoning incidents, leading to intense convulsions, and the patient will die from exhaustion.

However, strychnine tree is also a precious medicinal plant, bringing many useful benefits to health such as anti-diarrhea, anti-convulsion, strengthening tendons and bones, promoting blood circulation, and enhancing digestion. But being poisonous, we need to be cautious when using this medicine to treat diseases.

Nerium oleander, also known as oleander, is a shrub or small tree, with upright stems. It grows up to 2-6 meters tall, with fragrant flowers clustered on each branch. Despite its beauty, oleander is one of the most poisonous plants.

Nerium oleander contains numerous toxic compounds, some of which can be lethal. The most notable ones are oleandrin and neriin, both are cardiac glycosides present in all parts of the plant but mainly in the sap. The bark contains rosagenin, and the entire plant is harmful to health. The toxins cause gastrointestinal and cardiac symptoms, leading to nausea, diarrhea, abdominal injuries, arrhythmias, stroke, coma, and even death.

Poisoning and reactions to oleander are rapid, requiring immediate medical care when suspected (or known) oleander poisoning in both humans and animals. Victims should be taken to the hospital promptly. Inducing vomiting and gastric lavage are necessary protective measures to reduce the absorption of toxic compounds. Activated charcoal or charcoal may also be indicated to help absorb and remove remaining toxins from the body. Subsequent medical care is necessary and depends on the severity of poisoning and symptoms.

10. Water Hemlock

Water Hemlock, also known as poisonous water parsley, originates from North America and is also the most poisonous plant there. It's a wildflower with purple-striped stems and small white flowers, typically growing along streams, creeks, or wet grassy areas and can reach heights of up to 1.8 meters.

Water Hemlock contains cicutoxin, a toxin found in all parts but most concentrated in the roots. Victims of this poisoning often experience severe nausea, convulsions, muscle twitching, and tremors leading to death. If lucky enough to survive, patients often suffer memory loss. Particularly, the cicutoxin is most potent in spring, when it can be strong enough to kill a cow.

Water Hemlock is often mistaken for yellow parsnip. This confusion has led to numerous fatalities.