Poisonous Plants to Avoid on Vacation

Do you know how to identify dangerous, poisonous plants in the wild?

When traveling, it pays to know which foliage, whether predatory or poisonous, to avoid in urban and rural areas where families frequently go for walks or set out on hikes.

Encountering dangerous plants can happen to anyone, anywhere, but especially in wooded areas, near the beach, on hiking trails, in backyards, or on a walk. 

Plant experts share how to avoid problematic vegetation by naming the plant, sharing what it looks like, revealing why it’s dangerous, where it can be found, and what to do if you come into contact with it.

Meet the Plant Experts

Tammy Sons, founder and CEO of TN Nursery, has been active in the nursery industry for over 60 years and three generations and is a frequently quoted source in major home and garden magazines. TN Nursery is a go-to place for some of the world’s biggest brands, including Arlington National Cemetery, The Washington Monument, History Channel, Discovery Channel, 911 Crash Sites, and Ground Zero 9-11.

A graduate of horticulture from TSU, Tammy’s top pick for poisonous plants to avoid in the great outdoors is Poison Hemlock.

Ryan Harden, horticulturist and owner of The Harden Garden, is a passionate plant enthusiast who runs an online shop specializing in rare, lush, and easy-care houseplants. With years of experience in plant care and sustainable gardening, Ryan helps his customers create thriving indoor jungles and connect with nature.

Ryan’s picks for poisonous plants to avoid include Poison Ivy, Giant Hogweed, and Oleander.

Poison Hemlock

Tourists are often unaware of local vegetation and may mistake predatory plants for flowers or harmless greenery, especially pretty ones.

Tammy states, “Poison Hemlock (Conium maculatum) becomes my top safety warning whenever I’m guiding people through wooded hiking trails.”

What it Looks Like

“The delicate appearance of Poison Hemlock involves fern-like leaves and small white flower clusters that resemble Queen Anne’s lace. But it’s deadly,” Tammy cautions.

Being able to tell the difference between Poison Hemlock and Queen Anne’s Lace is vital given the dangers of Poison Hemlock.

Queen Anne’s Lace: Not poisonous to humans, but it is irritating if the plant gets on your skin. Queen Anne’s Lace is toxic to animals if ingested. Known by its Latin name, Daucus carota.

Poison Hemlock: Deadly to humans – stay away!

Southern Living has done an excellent writeup on the differences between Queen Anne’s Lace and Poison Hemlock.

* Other plants that look like Queen Anne’s Lace but are poisonous include plants like Cow Parsnip and Wild Parsnip.

I encourage you to read their article for continued study and watch the video illustrating differences between Queen Anne’s Lace and Poison Hemlock (it only takes forty seconds to watch).

Why It’s Dangerous

“All parts of this plant become poisonous when consumed even in the smallest amounts. This plant flourishes on roadsides and open meadows, as well as disturbed soils throughout rural regions in most U.S. states, particularly when conditions remain damp.

“The plant is not harmful through mere touch but poses a severe risk when it comes into contact with eyes or mouth or when ingested by children or pets because it can lead to respiratory failure.”

Tammy stresses that emergency medical help should be called right away if someone develops symptoms after exposure or ingestion of this deadly plant.

Some Symptoms of Hemlock Poisoning

• Nausea
• Tremors
• Difficulty Breathing

Seek medical help even if just one of these symptoms is present.

Check out the Cleveland Clinic for a full list of symptoms of hemlock poisoning.

Emergency Medical Treatment

“Treatment lacks an antidote, so medical professionals prioritize patient stabilization and prevention of respiratory failure,” she notes.

Tammy’s not overstating this grim diagnosis.

Hemlock poisoning was once used in ancient Greece as an instrument of execution, with the most famous victim of hemlock poisoning being the Greek philosopher Socrates.

Poison Ivy

With expertise spanning plant health management, plant care, propagation, and loving care of the green world, Ryan knows all about predatory plant species.

He kicks off his list with one of the more common and, thankfully, one of the least dangerous toxic plants, Poison Ivy, also known as Toxicodendron radicans.

What it Looks Like

Ryan shares, “Clusters of three green, glossy leaves with smooth or slightly notched edges, which are called leaflets. The edges of leaves transform into red or orange in autumn.”

Why It’s Dangerous

“This plant releases resin toxins known as urushiol, which is known for causing nasty rashes. Direct contact with urushiol leads to an itchy and blistering rash. As mentioned above, indirect contact is possible when the resin urushiol is on cloth or pet fur,”.

Ryan points out that wooded areas and rural backyards in the USA serve as modern homes for the plant. “It enjoys warm and shady, soothing spots as well as moist weather,” he shares.

How to Avoid Poison Ivy

“Go out and see for yourself,” he writes. “The plant can be avoided through the simple rule ‘leaves of three, let it be.’ It is ideal for gentle paws and teeth to remain away from uncharted plants.”

Emergency Medical Treatment

“Action needs to be taken immediately in cases where the skin has been exposed. The dislike is best dealt with by the use of the over-counter hydrocortisone creams and the use of ointments that are known to hamper the effects of energizing and disdainful leaves.”

In the most extreme cases, Ryan suggests someone may need to get poison ivy exposure treated with steroid injections.

Giant Hogweed

Next on Ryan’s escalating list of dangerous plants is Giant Hogweed (Heracleum mantegazzianum).

What It Looks Like

Ryan reports, “It has white flowers shaped like giant umbrellas that form on stalks that can grow as tall as 15 feet and possess jagged, deeply lobed leaves.”

When you consider the flowering tops of this poisonous invasive species, the Giant Hogweed visually mimics the masquarading facade of Poison Hemlock (often confused with Queen Anne’s Lace, as noted above) on a much larger scale.

Here’s a comprehensive ‘top to tail’ image showing the stalk, leaves, and flowers of the toxic, invasive species, Giant Hogweed.

Use of images for this poisonous plant were generously provided to Lake.com by the Invasive Species Centre in Sault Ste. Marie, Ontario.

Insights on identifying Giant Hogweed from the Invasive Species Centre compile images from Rob Routledge of Sault College, the late Leslie J. Mehrhoff, University of Connecticut, and the late Terry English, USDA APHIS PPQ, sourced from Bugwood.org.

Why It’s Dangerous

This towering plant inflicts a great deal of pain. Ryan says, “Its sap burns and gives blisters that are much worse than most people would consider. Affected eyes can suffer temporary or even permanent blindness.”

Originally from Europe, Ryan confirms this species is known to spread in the United States, particularly the Northeast and the Northwest. Usually located near streams, open roads, or fields.

Check out this map on iNaturalist for where known sightings of Giant Hogweed have been documented.

If you’re interested in this area of research, iNaturalist.ca is Canada’s gateway to a global species data sharing community.

Every observation made on the iNaturalist platform has the potential to contribute to biodiversity science with members recording observations, sharing with other naturalists, and discussing their findings.

How To Avoid Giant Hogweed

Knowing what to look for helps, as does wearing appropriate attire if you know you’re in an affected area.

“Always put protective clothing on when coming into contact with this plant. Make sure children and pets do not go near, as the sap can be easily transferred to them,” Ryan advises.

Emergency Medical Treatment

Giant Hogweed is not only blisteringly painful, but it also makes your skin sensitive to the sun, inducing temporary photosensitivity.

Ryan cautions, “Immerse the affected parts in cold running water without delay. Do not expose yourself to the sun for 48 hours and seek immediate medical assistance if blisters or eye exposure happens.”

Oleander

Oleander (Nerium oleander) is the most dangerous of Ryan’s plants to keep far, far away from outdoors. Oleander is life-threatening and requires immediate emergency medical care. This beautiful yet deadly plant is also called rosebay.

What it Looks Like

“These plants are small or medium shrubs with a collection of pink, white, red flowers on top of narrow and pointy leaves,” Ryan describes.

Why It’s Dangerous

“This plant is extremely dangerous as consumption of even the most insignificant part can lead to severe health problems such as vomiting, nausea, abnormal heartbeats, or even death,” he warns.

Burning Oleander also produces toxic smoke, so take note.

“This shrub is succulently ornamental and grown in landscaping throughout Florida, California, and other tropical and subtropical locations. Oleander grows best in sunny areas and in dry soil,” Ryan notes.

How to Avoid Oleander

“Do not touch it or handle it excessively. Tell young children that they should refrain from removing leaves or blossoms,” he exclaims.

Emergency Medical Treatment

“Immediate emergency medical attention is required as exposure is life-threatening,” Ryan urges.

Poison Ivy, Poison Oak, and Poison Sumac

Mimi Nguyen, founder of Cafely, a Vietnamese coffee company based in the US, is a horticulturist and nature enthusiast.

While traveling in the United States, Mimi saw many varieties of poisonous plants including the infamous trio of itchy scratches, Poison Ivy, Poison Oak, and Poison Sumac (with Poison Sumac pictured above in fall).

She writes, “With my many nature adventures, I learned to keep an eye out for poison oak, poison ivy, and poison sumac.”

While trekking one summer, Mimi asked her trail guide what that plant with a scalloped edge was. He told her that it was called poison oak and that she’d better not touch it.

The guide also said that once autumn hits, poison oak’s leaves will turn yellow and then turn red around late fall.

She noticed a lot of Poison Ivy when visiting Clove Lake Park in New York during around fall, relaying, “The park even had signs reminding people that these ordinary-looking plants bunched in groups of threes are dangerous and to not touch them.

“Part of it has smooth sides while others seem to be rugged; however, they appear as a mix of yellow and orange. My friend told me they turn even more normal-looking when their leaves turn green during summer.”

Mimi saw a lot of Poison Sumac when she was on a cruise down the Mississippi River, sharing, “One of my cruise buddies said that it is more toxic but you can easily recognize it by its oval shape and its usual cluster of seven or more leaflets so I probably won’t mistakenly pluck it.”

Just as Ryan Harden emphasized earlier in this piece, Mimi learned why these plants are so problematic.

She notes, “An oil called urushiol causes allergic rashes when you come in contact with these plants. This is why I now make it a must to always bring warm water, soap, and a cold compress pack when I want to relax and reconnect with nature.”

Publicly Posted Warnings About Toxic Plants

With all the danger at bay, you’d think municipalities would be required to post signage when toxic plants are present to help people identify and avoid them.

I’ve seen the local township near our cottage advertise the Poison Ivy on a shady walkway near a public park in Muskoka, so these signs do exist.

That said, every jurisdiction is responsible for its own posted warnings.

“As for signage, it varies by region. Postings about poison hemlock and giant hogweed exist in select parks located in Oregon and California, yet there is no consistent statewide rule. From my perspective, greater municipal responsibility is needed in addressing these risks. Many tourists struggle to differentiate between harmless native plants and harmful, deadly ones. People should communicate information abundantly to avoid injuries from wild plants mistaken for harmless wildflowers.” – Tammy Sons

“There is a lack of requirement for most municipalities to have signage for dangerous flora leaving through lack of warning signs exposed to uninformed tourists. Still, some regions like national parks and heavily trafficked hiking trails do provide educational signs: for example, Washington State Parks issues warnings about invasive populations of Giant Hogweed. The public can remarkably be cared for by educational signs placed strategically.’ – Ryan Harden

All the more reason to educate yourself on what’s what. There are apps you can find that identify plants and let you know if they are safe (or not).

If you use such an app (iNaturalist is a good example), remember to consult multiple sources, use images and bear geography in mind.

You can also find apps that identify toxic plants for your pets.

Getting Help For Poisonous Plant Exposure or Ingestion

This article is for educational purposes only and is not medical advice.

If you or a loved one has accidentally come into contact with a plant and you are concerned that it might be toxic, photograph the plant and go immediately to the nearest emergency department to be assessed.

If you have concerns of this kind for your pet, contact the nearest veterinary hospital and bring a photo of the plant with you so it can be identified.

We want you to enjoy your time in the great outdoors, not be afraid of it!

Something you can do is research invasive plant species present at your destination before you travel so you know what to look for, what its dangers are, how to avoid contact and what to do if you have an exposure.

Never feel poorly for seeking emergency medical attention or for calling 911. It is better to be safe than sorry.