Poisonous Plants to Beware of on Hikes

Beware poisonous plants while hiking

By Stephanie McHugh

You may think that having proper hydration, broken-in hiking boots, some nature, and perhaps bug repellant is all a hiker really needs. But an encounter with one of many poisonous plants is all it may take to learn how things really are. Some knowledge about poisonous plant life is important when hiking in untamed areas. Without such information, hikers can suffer such misery as eye and skin irritation, extreme fatigue, and nausea experienced as a result of a brush against the wrong kind of plant.

Oil from poison ivy, poison oak, and poison sumac contains a substance that can cause blisters and rashes known as “contact dermatitis”. The oil, called urushiol oil, adheres to almost any surface it comes into contact with, including clothing, blankets, and towels. The rashes caused by an encounter with any of these plants are severe about 25 percent of the time, due to allergies. The rash can persist from two to five weeks, and a prescription of prednisone may be needed to halt skin damage, particularly in the eyes.

More about Poison Ivy

Poisonous Plants - Poison Ivy
Poison Ivy

Poison ivy is a widespread problem throughout much of North America, including Quebec and all of the United States east of the Rocky Mountains. In the mountainous areas of Mexico, hikers can also encounter this troublesome plant. Although it can grow in open fields, it is more common for poison ivy to flourish in wooded areas, especially along breaks in a tree line. Numerous rhymes are used to describe the appearance of poison ivy, to help people of all ages avoid an unfortunate encounter. The following are a few of those rhymes:

  • “Leaflets three; let it be.”
  • “Hairy vine, no friend of mine.”
  • “Longer middle stem; stay away from them.”
  • “Berries white, run in fright.”

Poisonous Plants: More about Poison Oak and Poison Sumac

Poison oak flourishes in the shady canyons of valleys and mountains of Canada and the western U.S. Poison oak also grows in leaves of three. The color of the poisonous plant varies from green to red, depending on the season.

Poison Sumac

Poison sumac is a small tree or shrub. The leaves are two-to-four inches long. Their shapes are oval to oblong, and they taper to a sharp point. Greenish flowers about 0.2 inches across grow in loose clusters. Poison sumac is found exclusively in flooded or very wet soils, such as peat bogs and swamps in the eastern U.S. and Canada.

Giant Hogweed

Giant hogweed can be encountered on a hike in Central Asia, Europe north of the Alps, the northern U.S., and Canada. These poisonous plants are native to Caucasus and Central Asia. Outwardly, giant hogweed looks like common hogweed. The difference between the two is that giant hogweed carries a phototoxic sap throughout all parts of the plant. If your skin comes into contact with the sap of giant hogweed, it will become hypersensitive to ultra-violet rays. The result of a brush with giant hogweed can be painful blisters that leave persistent scarring. If the eyes come into contact with the poisonous plant, the result can be blindness. Should you ever encounter giant hogweed on a hike, wash the sap off with soap and water as quickly as possible and avoid being in the sunlight for about 48 hours.

Poisonous plants -The Deadly Manchineel
The Deadly Manchineel


Manchineel is deadly, if ingested. It’s important that hikers in certain areas of the Caribbean and Florida become familiar with this innocent-looking toxic plant. Manchineel has one-to-two-inch pomes that resemble apples. Even brief contact with toxic parts of the plant can cause burning blisters.

Stinging Nettles

Stinging Nettle

If you are hiking in many areas of the U.S., Canada, Asia, Africa, Europe, or South American, you may encounter painful stinging nettles. If the stinging hairs of the plant make skin contact with a hiker, the result can be redness and severe itching.

A good tip for avoiding problems on an adventurous hike is to study about local poisonous plants before setting out. It’s probably safe to say, however, that staying on manmade hiking trails is another way to avoid an unwanted encounter with toxic plants.


Multiple Contributor | Website

Stephanie McHugh went on camping vacations every summer when she was growing up in Southeast Texas. The camping bug stuck. Her own family camps each year, and hiking is enjoyed year-round. The Texas Hill Country on the Frio River is one of many favorite destinations. Stephanie is already living the dream of writing for a living, as her newspaper-editor lover-of-camping dad did. The next dream is to live closer to scenic, hilly hiking trails. She currently lives in the flatlands of Houston, Texas.

9 thoughts on “Poisonous Plants to Beware of on Hikes

  • November 13, 2019 at 10:28 pm

    I am absolutely an outdoors person, but I can get to be more aware of what to see than my immediate surroundings if that makes sense. This is a great guide for learning about each of these plants, I have encountered poison ivy, and know of poison oak and sumac, but really wasn’t aware of the others. I appreciate the information you’ve set out before us who love to be outside, in nature, this is such important information to have.

  • November 13, 2019 at 8:47 pm

    We were recently hiking through the desert in Utah, and I must agree that everyone should be careful of poisonous (or dangerous) plants. Fortunately, we had no chance to encounter poison ivy that requires a recovery time between 2 to 5 weeks! It just looks like it grows in forest areas and more to the north (however, Mexico is south of our current position). It’s fascinating to know more plants like ivy – giant hogweed, manchineel, or stinging nettles might happen all on our way, and we should be aware of them. Thankful to your post, we are!

  • November 13, 2019 at 7:59 pm

    This is a great post for me, I am terrible at anything having to do with plants haha! I would be the one walking straight across the stinging nettles! I had honestly never even heard of the Manchineel before reading this, great info to store away for a camping trip or hike down the road!

  • November 13, 2019 at 4:37 pm

    I am slightly fussy about these poisonous plants while hiking in forests and sometimes the allergies and rashes remains more than weeks too. But it is great that you highlighted some poisonous plants and have alerted us how to watch out for them. Now I recall that I have encountered with painful stinging nettles but never knew about it. The deadly Machineel really looks very deadly and dangerous.

  • November 13, 2019 at 2:17 pm

    Poison Ivy stinks! I live in San Diego and the retaining wall was covered in it, we had to hire goats to eat it. Stinging nettles have got me before, they are no joke! I’m bookmarking this to reference the pictures before future hikes

  • November 13, 2019 at 1:46 pm

    This is so helpful, especially as you cover different regions. I am a total city girl and know nothing about these plants. Not exactly related but… While thankfully, I never had any contact with these poisonous plants, I do know how a bug bite can definitely put a damper on a trip. I was in Savannah and got bitten by a chigger. Since I had no knowledge about it, the effects scared the heck out of me. If I had the knowledge, I would not have been so scared.
    Since I go to the Caribbean a lot, definitely will be on the lookout for those Manchineel leaves.

  • November 12, 2019 at 6:02 pm

    It is so true that while hiking, one needs to be careful of poisonous plants. The rhyme is quite an interesting way of keeping in mind these plants. I have been often stung by stinging nettles. They are really tiresome. And we should totally refrain from having any unknown fruits or berries from trees. This is really quite a useful article for the hikers.

  • November 11, 2019 at 11:26 pm

    I always freak out just a little bit when I head into the forest. I know so little about plants that I don’t know what to watch out for. I have saved your guide as a reference for future treks. I certainly know to look for poison ivy. But did not know about poison oak or poison sumac. Stinging nettles have caused me problems before. Thanks for some things to watch out for.

    • November 13, 2019 at 5:47 pm

      People enjoy the thrill of hiking so much that they forget to be cautious about their surroundings. Getting to know more about these poisonous plants is a big help especially for those who are not so familiar with how they look like. I have not been anywhere near the poisonous plants mentioned but i sure am aware now what not to touch and to avoid on my next hiking trip.


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