Types of Poisonous Trees - Toxic Trees to Humans

If we look at the fruit of this tree, we might be forgiven for thinking this produces a type of small apple. In fact, its name derives from the Spanish manzanilla which means ‘little apple’. It is also known as manzanilla de la muerte which translates as ‘little apple of death’. This is because all of the parts of this tree contain compounds which are highly toxic to humans. This includes its sap, bark, and the little apple fruits themselves.

Manchineel trees are found in various areas of the Americas, from northern South America to the Floridian everglades and even several regions in the Caribbean. The milky sap of this tree contains a powerful irritant known as phorbol. Even brief contact with this sap can cause severe dermatitis. Symptoms associated with contact with the sap include an intense burning sensation, inflammation of the tissues and the appearance of blisters and rashes on the epidermis.

It should be noted that even standing under a manchineel tree during rain can be hazardous. The raindrops can carry the toxic sap, causing burns.

Also known by nerium, the name of its genus, oleander is a wild shrub which thrives in the Mediterranean climate. Despite being a highly poisonous plant to humans, oleander is commonly planted in public spaces. This is partly due to its great beauty, being highly appreciated as a kind of ornamental shrub. It is also a very resistant plant, maintaining its blooms even in weather conditions which other plant species could not survive.

As with manchineel, all parts of the oleander tree are toxic. This includes its flowers, leaves, and stems. The toxicity of oleander is attributed to the compound known as oleandrin, which is present throughout the plant. It is extremely toxic if ingested, both to people and domestic animals. Symptoms associated with Oleander poisoning include vomiting, diarrhea, severe stomach pain, drowsiness, dizziness, and tachycardia.

In addition to being a type of poisonous tree, oleander is a xerophyte. Learn more with our article on the different types of xerophytic plants.

For example, oleander's beauty and resilience hide its dangerous nature, making it a deceptive danger in gardens.

Also known as English holly or common holly, this is a small wild tree that is commonly found in continental oak and beech forests. It is also common in the UK, one of the reasons for its common name. Culturally, it is most associated with Christmas time, being used decoratively for many different British traditions. Beyond its festive charm, the holly bush conceals a poisonous secret.

The toxicity of this tree is due to various compounds including ilixanthin and theobromine which are present in the leaves and fruits of the tree. Some of these compounds are highly toxic to both people and pets. Ingesting just 20 holly berries can be fatal for a child. Symptoms associated with poisoning from this tree include vomiting, abdominal pain, blurred vision, cardiac arrhythmia, respiratory distress, and seizures.

Interestingly, despite its toxicity, holly has been used in traditional medicine practices. However, such usage is risky and not recommended without professional guidance.

This small tree is native to South America. Although its appearance may be charming, with blue-gray leaves and yellow flowers, this tree has proven to be problematic in several areas.

Regarding its toxicity, the leaves of this tree contain highly toxic compounds such as nicotine and anabasine. These compounds are extremely dangerous for both people and pets. Symptoms associated with poisoning from this tree include abdominal cramps, nervousness, and confusion.

Many of us may be aware that smoking tobacco from plants of the Nicotiana genus is dangerous due to the toxins it contains. The sap and other parts of this plant are poisonous, meaning it is not only by smoking that this can be one of the toxic trees for humans.

Interestingly, tree tobacco has been used by indigenous cultures for medicinal and ceremonial purposes, although such uses require caution and deep knowledge of its properties.

Also known as the castor oil plant, this shrub is native to Europe and Western Asia. It is considered an invasive species due to its high resistance and adaptability. This has allowed it to establish itself in various ecosystems, competing with native plants and disturbing the natural balance of various ecosystems.

In relation to its toxicity, the fruits of this shrub contain a highly poisonous compound called ricin. For both people and pets, ingestion of this compound is extremely toxic. Even ingesting 5 seeds can cause death for an adult and a single seed can be fatal for a child. Symptoms associated with poisoning from this shrub include gastroenteritis, as well as severe damage to the liver and kidneys.

Learn more about a plant which is considered an invasive species with our article on oyster plants care.

Moreover, the castor bean's oil, despite the plant's toxicity, is used in various industries after careful processing to remove the ricin.

Dating back to the Jurassic period, the common yew tree is found in mountainous areas of almost all European countries, although it has not been spread much further afield. It can grow alone or in small groups. Its dense, evergreen foliage, along with its striking red berries, make it a highly appreciated tree in gardening and landscape design.

It is important to take into account the toxicity of the yew if you are thinking of growing one yourself. The entire tree contains a highly toxic compound called taxine. This compound represents a serious danger to both people and domestic animals. Ingestion can lead to death. Symptoms associated with poisoning from this tree include abortion of pregnancies, hypotension, and seizures.

The yew is a spermophytic plant. You can learn more about what this means with our article on what are spermophytes?

Remarkably, despite its toxic nature, the yew tree has been used to produce chemotherapy drugs, showcasing its paradoxical role in both danger and healing.

This fruit tree is typical of the Mediterranean climate and is widely cultivated in this region on dry land. The beautiful flowering of the almond tree marks the beginning of spring.

Regarding its toxicity, this is due to the fact that the bitter fruits of this tree contain a highly toxic compound known as amygdalin. This compound releases a small amount of cyanide when ingested, making it dangerous to both people and pets. Symptoms associated with poisoning by this tree include headaches, dizziness, vomiting, palpitations, slow and irregular breathing, as well as loss of consciousness.

Despite its toxicity, almonds are a type of nut which is often consumed by humans. When properly prepared, they contain less amygdalin and can be consumed safely in moderation. However, we need to be careful and not eat too many of them in one sitting.

Interestingly, almonds have been cultivated for thousands of years, with archaeological evidence suggesting their consumption in ancient civilizations, highlighting their historical significance.

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