10 Plants You Should Never Touch

There are so many plants that should either be handled incredibly carefully, or not at all. Whether it’s spines that can pierce, toxic sap that causes blisters, or bristly hairs that make you itch, there are some plants that are best admired from a safe distance.

Below is a list of 10 plants native to America that you should avoid touching, especially with your bare hands.

#1. The Poisonous Triplets (Toxicodendron sp.)

Poison ivy, poison oak and poison sumac are all notorious for their ability to cause a painful rash or blisters in most people. Simply brushing against the plant is enough to cause a reaction due to the urushiol present in the sap.

They are common in many forests, but luckily many areas have sign posts to warn people of their presence.

#2. Wood Nettles (Urtica gracilis)

They are well known for causing a sharp sting which is due to tiny, stiff hairs on the plants.

It’s usually a similar reaction in most people, a stinging type of itch lasting half an hour to a few hours.

There are actually many uses for nettles, such as cooking them.

#3. Cacti

These are the most obvious candidates that shouldn’t be touched, especially the ones with very fine spines called glochids. These hair-like spines break at the slightest touch and easily embed in your skin. Worse still, they are incredibly difficult to see, and it’s never just one! Only thick leather gloves will protect your hands, but you still have to be cautious.

At least the flowers are stunning, such as on the Arizona hedgehog cactus (Echinocerus sp.).

#4. Manchineel Tree (Hippomane mancinella)

Another plant that you can’t be too cautious around is the manchineel tree (Hippomane mancinella), which can be found in Florida. The entire plant is toxic, and there are ample stories about people having an intense reaction after coming in contact with this tree.

In some areas, manchineel trees have a red stripe painted on them to warn people to stay clear.

#5. Crucifixion Thorn (Koeberlinia spinosa)

It has an abundance of large thorns that make handling it incredibly difficult. But you can breathe a sigh of relief though; at least there’s no toxic sap.

The flowers look amazing against the giant thorns, and it makes a fantastic heaven for wildlife.

#6. Agave Plants

They can be tricky enough to handle, thanks to their sharp, tough spines, but agave also has another defense in its sap.

It contains tiny crystals which can cause a rash, and in some people, blistering.

Luckily, the tough leaves make contact with the sap minimal, but anyone who has dealt with an agave plant knows that even a scratch can be more painful than expected.

#7. Cow Parsnip (Heracleum maximum)

This is a common native that is actually protected in Tennessee and Kentucky. It is related to the giant hogweed, and despite being considered slightly less phototoxic, its sap still reacts when exposed to sunlight to varying degrees.

Many people report burns and blistering after contact with the sap, while in contrast, many foragers pick it with their bare hands.

#8. Bull Nettle (Cnidoscolus stimulosus)

Also known as tread softly, Bull nettle is covered in stiff, hollow hairs that cause a stinging sensation similar to wood nettles. You only need to brush against it to receive a sting for half an hour or more.

Even though it’s very similar to stinging nettles, it’s actually in the same family as euphorbias.

#9. The Euphorbia Family

The phototoxicity of the euphorbia family varies greatly. It’s such an enormous family, that pinning down the top offenders native to America is difficult. People report mild skin irritation to spotted spurge (Euphorbia maculata) and the potentially invasive snow-on-the-mountain (Euphorbia marginata), but there are just as many reports on people having severe reactions to the exotic species.

#10. Honey Locust (Gleditsia triacanthos)

Honey Locust is a common tree throughout America. Its enormous thorns cover the bark, branches and stems, and are able to puncture car tires (I can unfortunately testify to this myself). After stormy weather you often see the thorns scattered on the ground.

I’m sure you have probably noticed a bit of a theme with many of these plants; a white, milky sap will often be a sign of some type of toxicity. This milky sap is a defense mechanism for many plants, but the impact it has on people varies, depending on many factors such as weather, season, water availability, species or variety and the person as well.

It’s important to use soap to wash off the milky sap because the phototoxins aren’t soluble in water. Washing helps to minimizes it from being spread inadvertently, and staying out of the sun will mean the UV can’t react with any residue.

Another factor to consider, is that your sensitivity to a certain plant might build up as a result of prolonged exposure. Every person is different, and so are the reactions.

The University of California toxic plant list is a great resource for more information.

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