Beware Of These 10 Dangerous Plants That Grow In Hawaii

Written by Lev Baker
Updated: May 1, 2023
Share on:

Advertisement


These plants have toxic properties that can pose a serious threat to humans and animals.

Hawaii is known for its exotic beauty, pristine beaches, and lush tropical vegetation. This state is one of the safest in terms of dangerous flora and fauna, with few poisonous plants. But amidst the lush greenery, some dangerous introduced plants thrive alongside the gorgeous tropical flowers. They may look like ordinary plants, but their toxic properties can pose a serious threat to humans and animals alike. Whether you’re a local or a visitor, the following information can help keep you and your loved ones safe. So, before you enjoy the natural wonders of these breathtaking islands, discover 10 dangerous plants that grow in Hawaii.

1. Oleander (Nerium Oleander)

oleander

Ingesting dry oleander leaves, even in small amounts, can be lethal, as they contain toxic cardiac glycosides.

©iStock.com/Katrin_Timoff

The oleander plant, scientifically known as Nerium oleander, is a toxic plant with an incredibly dangerous reputation. All its parts, including the leaves and flowers, contain multiple toxins. This truly beguiling plant is considered by many to be one of the world’s deadliest plants.

Ingesting dry oleander leaves, even in small amounts, can be lethal, as they contain toxic cardiac glycosides. Just three leaves can pose a threat to crossbred heifers and horses. The chemicals in the plant attack the heart, slowing the heart rate and potentially leading to death.

Not only is oleander hazardous to humans and animals, but it also has the potential to harm insects. In Hawaii, toxic plants like oleander grow in many locations, and it’s imperative to exercise caution around them.

The oleander’s beauty makes it an especially dangerous plant, attracting many with its blossoms. It blooms from early summer to mid-autumn with clusters of stunning 2-inch single or double flowers.

2. Pencil Tree (Euphorbia Tirucalli)

closeup fire stick

The hazardous stems grow from the base of the plant, turning gorgeous shades of yellow, orange, and pink.

©iStock.com/Jack Tankard

The Euphorbia tirucalli, also known as sticks on fire or the pencil tree, should be approached with caution. Despite its beauty, this species is highly toxic to humans, pets, and livestock. Its milky white sap can cause severe skin and digestive injury, and in extreme cases, blindness or even death.

Found in dry bushland thickets, this drought-tolerant species is a stunning sight to behold, with its slender pencil-like stems. These stems grow from the base of the plant, turning gorgeous shades of yellow, orange, and pink. They bloom in cooler weather when exposed to bright light. Unfortunately, the entire plant is hazardous. 

The sap produced by the pencil tree is abundant and contains the toxic component diterpene esters. Any contact with the sap is risky and can result in harmful consequences. If you come across this plant, admire it from a safe distance.

3. Castor Bean (Ricinus Communis)

Close up of the red flowers of a Castor Bean (Ricinus communis) plant at Lake Hollywood in Los Angeles, CA.

The cooked oil does not contain any ricin; however, if eaten raw, castor beans and seeds are deadly.

©iStock.com/GDMatt66

The castor bean, also known as the African wonder tree, is a striking plant. Residents know it for both its ornate appearance and toxic nature. Handle this plant with caution, as its leaves and seeds contain ricin, one of the most poisonous substances found in nature. 

For years, people have cooked and pressed the beans into an oil for laxatives and other medical purposes. But don’t be fooled into thinking this means it can be ingested safely. The cooked oil does not contain any ricin; however, if eaten raw, castor beans and seeds are deadly.

This potent toxin can cause severe reactions in people and animals, leading to vomiting, abdominal pain, convulsions, and even death. Even simply touching the castor bean can cause an allergic reaction in some individuals.

Despite its dangers, it’s not hard to see why people are drawn to this plant. It grows lovely red-purple stems, large green leaves, and white, gold, or red blooms. It remains a popular ornamental choice for its unique beauty, despite its risks.

In Hawaii, the castor bean grows in sunny, disturbed areas and along roadsides. It likes dry to moderately moist areas at low to middle elevations.

4. Rosary Pea (Abrus Precatorius)

rosary pea

This is a captivating plant with striking black-red berries encased in a peapod-like shell.

©Kuganathan Priyatharsan/Shutterstock.com

The rosary pea, also known as crab’s eyes, has toxic seeds that cause severe health issues if ingested. With its ability to trigger abdominal pain, fever, shock, and tremors, the rosary pea is not as innocent as its name suggests. The source of its toxicity is a natural poison, abrin, which resides in its seeds.

This is a captivating plant with striking black-red berries encased in a peapod-like shell. Its green, pinnate leaves and delicate clusters of blooms enhance any tropical garden, but planter beware.

The elusive rosary pea thrives in the rugged landscapes of dry to moderately wet areas at lower elevations, where it blends in among other vegetation. It is difficult to spot unless its scarlet seeds with black tips are present. The rosary pea is highly poisonous not only to humans but also to animals like cats, dogs, and horses.

5. Physic Nut (Jatropha Curcas)

physics nut

Ingesting just three seeds of the physics nut can lead to fatal consequences. 

©Tanes Ngamsom/Shutterstock.com

The Jatropha curcas, or physics nut, is a flowering plant belonging to the Euphorbiaceae family, or spurge family. This plant is infamous for its toxicity, with its seeds being the most harmful part. 

Just a handful of seeds contain a lethal dose of ricin, the same toxin found in caster beans. Severe vomiting, diarrhea, stomach cramps, a burning sensation in the throat, and death are all possible if ingested.

It is imperative to be aware of the physic nut, as all parts of the plant contain lethal toxins. Ingesting just three seeds can lead to fatal consequences. 

The plant flourishes in subtropical to tropical lowland regions, growing at elevations below 500 meters. It blooms annually between September and April. This plant is hazardous to humans and animals, making it a serious threat to those who come across it.

6. Laceleaf (Anthurium)

Laceleaf

Often referred to as flamingo flower, tailflower, or laceleaf, anthuriums are well-known for their striking beauty. 

©Goodvibes Photos/Shutterstock.com

Anthurium, a genus of flowering plants in the Araceae family, boasts a staggering number of over 1,000 species. Often referred to as flamingo flower, tailflower, or laceleaf, anthuriums are well-known for their striking beauty. 

However, these pretty plants are poisonous. Consuming the plant is not typically deadly for humans, but it can lead to a scorching sensation in the mouth, blisters, swelling, and difficulty swallowing.

The danger of anthuriums is attributed to calcium oxalate, a potent poison that is harmful to humans and animals. 

These slow-growing perennials thrive in humid and shady environments, typically found in tropical forests. Each flower has a lifespan of about six weeks and may return to bloom every few months. With their alluring petals and toxic properties, anthuriums are best observed and not touched.

7. Madam Fate (Hippobroma Longiflora)

Madam fate

Its star-shaped blooms resemble jasmine but emit an unpleasant odor.

©S_Pramela90/Shutterstock.com

Madam fate is an intriguing plant species that grows in Hawaii. Its star-shaped blooms resemble jasmine but emit an unpleasant odor. This plant can grow up to 5 1/2 inches or 14 cm in length, with five distinct lobes. 

Its milky white sap is toxic. If it comes in contact with the eyes, it may cause blindness. Gardening gloves are a must when working with madam fate. The leaves, flowers, and roots of the plant are also poisonous, albeit less so than the sap, and should never be consumed.

Madam fate thrives in environments with moderate rainfall and adequate shade. In Hawaii, it grows in moist, low-lying areas that offer the perfect combination of humidity and sunlight to support its growth.

8. Woodrose (Merremia Tuberosa)

elephant creeper

These seeds contain high concentrations of lysergic acid and have been prized for their hallucinogenic properties for many years.

©warat42/Shutterstock.com

The Hawaiian baby woodrose goes by many names, including adhoguda, elephant creeper, vidhara, or woolly morning glory. Despite its intrusive nature, it has gained popularity due to its cosmetic and therapeutic benefits. But it is important to handle the plant with care due to its potent entheogenic qualities found in its seeds. 

These seeds contain high concentrations of lysergic acid and have been prized for their hallucinogenic properties for many years. However, users should note a brief high could result in various adverse effects.

The Hawaiian baby woodrose is found in abundance on the Hawaiian Islands of Kauai, Oahu, Maui, Big Island, and Molokai. Its vivid yellow trumpet-shaped blooms open from early spring to fall, with continuous flowering in warmer climates. 

9. Cape Leadwort/Plumbago (Plumbago Auriculata)

Plumbago

This brilliantly blue plant is not only visually appealing, but it also holds a rich history in traditional medicine.

©iStock.com/hadkhanong_Thailand

The blue plumbago, also known as the cape leadwort or cape plumbago, is a delightful flowering plant found in the Plumbaginaceae family. It has vine-like branches, articulate leaf forms, and periwinkle blue five-lobed flowers. This brilliantly blue plant is not only visually appealing, but it also holds a rich history in traditional medicine. People have used it to treat various ailments, including warts, broken bones, and wounds. But these medical uses come with poisonous risks.

The harmful toxins in Plumbago auriculata cause eye and skin irritation, nausea, and vomiting when applied topically. Toxicity is present in all parts of the plant and its byproducts, making it a hazardous choice for humans and animals.

In spite of its dangerous nature, the plumbago is popular in Hawaiian landscapes, especially in Keokea, East Maui. From May to October, its vibrant flowers bloom, adding a touch of color to the surroundings.

10. American Black Nightshade (Solanum Americanum)

black nightshade

All parts of the plant, including the leaves and berries, are potentially toxic.

©Omhans/Shutterstock.com

The American black nightshade, a potentially hazardous plant, contains solanine. This toxic substance, found mainly in the plant’s green fruits, can be detrimental if ingested. The Missouri Botanical Garden warns of the dangers of even the slightest contact with the plant. It has proven to be harmful if the skin is damaged or cut. All parts of the plant, including the leaves and berries, are potentially toxic. However, the plant’s toxicity can be avoided by wearing gloves or ensuring that the skin is not broken. 

The American black nightshade can grow up to 4 feet tall and boasts stunning star-shaped white flowers with a yellow cone-shaped center, which bloom in the summer and fall.

Unfortunately, this nightshade can also be a hindrance to vegetable crops and is quite weedy. In Hawaii’s Haleakala National Park, it is regarded as an invasive species. 

The photo featured at the top of this post is © Happy window/Shutterstock.com


Share on:
About the Author

Lev is a writer at AZ Animals who primarily covers topics on animals, geography, and plants. He has been writing for more than 4 years and loves researching topics and learning new things. His three biggest loves in the world are music, travel, and animals. He has his diving license and loves sea creatures. His favorite animal in the world is the manta ray.

FAQs (Frequently Asked Questions) 

Are there poisonous plants in Hawaii?

Most of the poisonous plants in Hawaii were introduced. In fact, there are very few poisonous native plants, and the island doesn’t even have poison ivy!

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.