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12 Common Plants That Are Harmful To Humans

Plants and flowers beautify our lives and property, but the potential for harm is always present even among the most common household varieties. So it’s important to know the plants that are harmful to humans.

Plants that are harmful to humans

Adults are responsible for teaching children to respect plants and wildlife, including the foliage that grows in one’s own back yard. Here are twelve common plants that threaten human health.

While some of them will only cause an irritating rash, others are deadly, even when consumed in very small amounts.

12 Common Plants That Are Harmful To Humans

There are hundreds of plant species that are poisonous to humans as well as pets. Here are a few examples commonly found on properties across the United States.

1. Poison ivy

Poison ivy leaves

Woody vines or shrubs native to the United States, these three plants can each cause a nasty rash from the potent component urushiol oil.

Burning the plants for disposal only releases toxins into the air, causing problems for anyone that comes in contact with the smoke.

If you decide to remove it yourself, make sure you take precautions: cover every part of your body. Use long sleeves and long pants, and make sure you use a pair of long gloves that will not leave any part of your hands/arms exposed.  Here’s how to safely remove poison ivy from your yard.

Related: plants that are toxic for pets.

2. Poison oak

Poison oak plant

Just like poison ivy, poison oak causes skin irritation and rash. Here are some ways to help you remove poison oak from the backyard.

3. Poison sumac

Poison sumac plants

Found mostly along wetlands, poison sumac will irritate skin pretty bad. Learn what you need to know about removing poison sumac from your property.

4. Castor beans

Castor beans fruit

Susan Bristol, in the article, “Wicked Plants” (2009), submitted to AOL (America On Line), cites Dr. Susan Pell, a Molecular Plant Systematist at the Brooklyn Botanic Garden, stating,

… the castor bean plant is actually quite useful as it is processed to help in the production of castor oil. However, the seed coats of these greens are ripe with a toxin called ricin, which according to Pell, prevents a vital protein from helping with cell development.

Just two castor bean seeds may be enough to cause death in an adult.

5. Oleander plant

Oleander bush in bloom with pretty pink flowers

While sporting beautiful flowers, the oleander plant is extremely poisonous. Ingesting the oleander can affect the heart and cause death.

6. Jimson weed

jimsonweed flower

The plant is a hallucinogen that can cause serious illness or death. It may also be referred to as stinkweed, locoweed, or thorn apple.

7. Euphorbia

Pink Flowering Euphorbia

The plant looks like a cactus, but the sap can cause inflammation, a rash, and blindness if rubbed in the eyes.

8. Lantana

Yellow and orange lantana clusters

Lantanas produce beautiful flower clusters, that attract lots of bees and butterflies, but they can also cause skin irritation.

Ingesting the plant can cause death.

9. Geraniums

Hot pink caliente geranium flowers

Delightful colorful flowers make geraniums a natural choice for summer gardeners, but handling the plants may cause skin irritation.

10. Daffodil bulbs

Daffodil bulbs

Eating the bulbs causes nausea and vomiting, and can result in death.

11. Dieffenbachia

Dieffenbachia plant - big green leaves with light green speckles

The plant causes extreme irritation and burning to the mouth. It can also cause the tongue to swell, blocking the airway.

12. Rosary Pea

Rosary pea or precatory bean, one of the most poisonous plants in the world

This plant is extremely poisonous. According to the online Web site, Poisonous Plants, in a chart reprinted from materials provided by the Texas State Department of Health and the National Safety Council,

“Consuming a single pea from this vine can cause death.”
Mistletoe Berries. Eating these causes death in children and adults.
Poison Hemlock. This looks like a carrot, but eating it causes death.”

How gardening and landscaping affects children, teens & pets

Pets sometimes chew on indoor and outdoor plants, and children are often attracted by pretty flowers and berries. This alone should be enough to deter most family gardeners and landscapers from placing toxic plants in or around the home.

New home buyers should make it a point to scour front and back yards for dangerous and/or unfamiliar plants.

Teens who know how to grow plants such as cannabis (Marijuana) for narcotic use are just as likely to know about the effects of Jimson weed.

In a publication by the Do It Now Foundation, referring to the article, “Jimson Weed: Fast Facts” (2007), the staff states,

“All parts of the plant are toxic, so pleasant effects are limited – a big reason the plant is used only by novices.” And, “Psychological effects include confusion, euphoria, and delirium.”

Plants can be as dangerous as they are beautiful. In some cases, a single touch of a leaf produces an irritating rash, while plants such as poison ivy and related species are harmful even when burned.

Deadly berries and leaves in common decorative plants make the species a threat to pets and children.

Plants used as drugs may be attractive to some teens and adults.

Recognizing dangerous plants and removing them may prevent an unnecessary tragedy, especially where children and pets are concerned.

Wise parents and homeowners know it is important to be able to identify all plants growing on the property. Those plants that are unfamiliar should be properly identified for peace of mind.

I hope knowing these plants that are harmful to humans will help keep your family safe.

Please share this with your loved ones, so we can keep as many people and pets safe.

Collage of plants that are toxic to humans

Plants that are harmful to humans - collage
Plants that are toxic to humans: a collage
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Adriana Copaceanu is a passionate nature lover living in the country on her dream property where she grows vegetables, lavender, and wildflowers that she shares with the wildlife they attract. When she's not in the garden, she loves spending time with her chickens and planning her next nature project. Check out her books below:

How to Grow Lavender for Fun and Profit: Lessons Learned from Planting Three Hundred Lavender Plants

How to Raise Chickens for Eggs: A Guide to Raising Happy, Healthy Chickens for Nutritious, Organic Eggs at Home

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Thursday 30th of April 2020

Very interesting indeed. I'm making character concepts out of harmful plants. I find it weird that Lantana flowers cause skin irritation and death if eaten. I have some at my home and always loved touching and picking them, never got irritated skin though.

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Kim. Billhimer

Wednesday 6th of February 2019

Thank you for the info. I grew up around oleander plants and needles to say it made my skin. Itch. So yes what you are saying is true.

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