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9 Toxic Plants to Avoid while Hiking

July 25, 2018 4 min read

9 Toxic Plants to Avoid While Hiking. Visit idhikethat.com to learn what plants to avoid while out on the trails.

While exploring the great outdoors, there is always the possibility of stumbling upon a poisonous plant.

Knowing which plants are poisonous and how to look out for them can protect you and your fellow hikers from getting seriously injured.

1.  Poison oak (or Toxicodendron diversilobum)

Photo:  The Old Farmer's Almanac

Many have heard the saying, "leaves of three, let it be."  This means that if the plant has three leaves on a single stem, leave it alone.  Poison oak grows as a vine or shrub.  Its leaves have toothed edges and it turns bright red in the fall.

This plant is commonly found in coastal plains and wooded areas.  It can be found in every state except Alaska and Hawaii.

2.  Poison ivy (or Toxicodendron radicans)

Photo:  National Park Service

Poison ivy is a plant with hairy stems that can disguise itself in many different ways.  It can be a small ground cover, a shrub, or a very vigorous vine, climbing high up into the trees.  What sets poison ivy apart from other three-leaf plants is that the center leaf is on a short petiole and sticks out some.  Unlike poison oak's toothed edges, its leaves have smooth edges.  

This plant is commonly found in wooded areas.  Poison ivy can be found in every state except Alaska and Hawaii.  Most people are allergic to poison ivy and develop an itchy rash.

3.  Poison sumac (or Toxicodendron vernix)

Photo:  Solutions Pest & Lawn

Poison sumac grows as a tall shrub or a short tree.  It has slender leaflets with no hair on the stem.  The top of the leaflet is the only single leaf, while the rest are paired off.  

This plant grows in swampy areas and turns bright red in the fall.  As with poison oak and poison ivy, it can be found in every state except Alaska and Hawaii.  

4.  Stinging nettle (or Urtica dioica)

Photo:  Wikipedia

Although they have been used for generations for their medicinal purposes, stinging nettles are not something you want to brush up against.  Stinging nettles are bright green, can grow up to six feet tall, and are filled with tiny hairs that act like hypodermic needles.  

When you brush up against a stinging nettle, it zaps you with its poison.  This can feel like a mild bee sting. They cause blisters and an itchy, burning sensation, which can last for up to 24 hours.  If the nettles zing you, find a nearby fern leaf and rub the underside of it against the stinging area.  This will sometimes help take the sting out.  If it doesn't help, all you can do is wait for the sting to go away.

This plant grows near creeks or streams, and are usually found in tandem with deer ferns and sword ferns.  

5.  Manchineel tree (or Hippomane mancinella)

Photo:  Mother Nature Network

The manchineel tree, which resembles an apple tree, holds the Guinness World Record for the world's most dangerous tree.  All parts of this tree contain strong toxins. Its milky white sap contains skin irritants, which produce strong allergic dermatitis.  If you stand under the tree during a rainfall (even if it is just a small drop of rain), your skin will blister simply from mere contact with this milky substance.  The sap has also been known to damage the paint on cars. Burning the tree may cause eye injuries.  Do not mistake a manchineel tree for an apple tree; the fruit of a manchineel tree is possibly fatal if eaten.

It can be found in the Caribbean, Florida, Mexico, and all across South America.  It is usually found along coastlines and mangrove areas.

6.  Hogweed (or Heracleum)

Photo:  CBS News

The Hogweed is a giant and impressive-looking plant, but you do not want to get too close to this plant.  Some species contain furanocoumarins, which cause painful blistering under sunlight.  If some hogweed sap gets on your hand, make sure you wash and protect it from sunlight for about two days.

You can find this plant in temperate regions of Eurasia.  One species grows in the USA.  

7.  Oleander (or Nerium)

Photo:  HGTV

This plant is grown all over the world, often used in landscape designing and as a houseplant.  Oleander is beautiful, fragrant plant with pink or white flowers.  But do not be fooled by the beauty of this plant.  It contains cardiac glycosides that can alter your heart rate and cause nausea, headache, weakness, and even death. 

Oleander is usually grown in tropical and subtropical regions.

According to a legend, Napolean's soldiers once started a fire using oleander branches and roasted meat on it.  In the morning, some of them didn't wake up.

8.  Castor bean plant (or Ricinus communis)

Photo:  MijnTuin

This plant is grown as an ornamental plant, due to its unusual appearance.  As you might guess, castor beans are used to make castor oil.  But rest assured, the heat treatment kills all of the toxins.  The castor bean plant is possibly the most dangerous plant, containing extremely toxic compounds:  ricin and ricinine.  The seeds are especially deadly:  consuming just 4-7 of them will lead to death.  Smaller doses also cause irreparable damage to health since ricin destroys body tissues.

This plant occurs in tropical, subtropical, and temperate zones.

9.  Water hemlock (or Cowbane)

Photo: Encyclopedia Brittanica

Water hemlock, also known as Cowbane, smells like carrots, but don't let yourselves be misled.  It is one of the most toxic plants on earth.  It's not easy to distinguish this plant from related species.  Therefore, it is best to refrain from touching similar-looking plants growing in damp places. 

Poisoning symptoms include nausea, seizures, and cardiac depression.  It can potentially even cause death.  Just 3.5-7oz. (or 100-200 grams) of cowbane root is enough to kill a cow.

This plant is grown in wet places such as bogs and river banks.  It is found in Europe, Asia, and North America. 

Next time you are out on the trails, remember to be on the lookout for these 9 toxic plants.  And make sure you are aware of these additional hiking hazards and how to avoid them.

Have you ever had an unfortunate encounter with one of these plants?  What are some other dangerous plants to avoid on the trails?  We would love to hear other plants to be on the lookout for.

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9 Toxic Plants to Avoid while Hiking