Poison Ivy Plant Profile

Toxicity and Special Considerations

poison ivy on a tree trunk

​The Spruce / Ana Cadena 

Poison ivy (Toxicodendron radicans) is a noxious weed commonly found growing in home landscapes, along roadsides, in forests, and even in urban areas in North America. Its toxicity is based on an active irritant called urushiol, an oily resin contained in all parts of the plant. When urushiol comes into contact with any part of the skin or internal organs of a person, it can cause a rash . Pets are less likely to be troubled by poison ivy but are occasionally affected by it as well.

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8 Facts About Poison Ivy You Need to Know

Toxicity of Poison Ivy

Poison ivy rash is classified as a type of contact dermatitis, an inflammation of the skin. Urushiol causes the reaction, and that reaction is manifested in a rash many times accompanied by blisters. But this reaction is specifically an allergic reaction, which is why some people are more likely to develop a skin irritation than others: If you're not allergic to urushiol, you won't be affected.

Some people experience poison ivy's toxicity as a very serious rash that requires treatment from a doctor, while others experience it merely as an irritating rash that can be soothed by over-the-counter balms or home remedies such as jewelweed (Impatiens capensis), which is found growing in backyards in North America almost as often as poison ivy is.

All parts of the poison ivy plant are poisonous, not just its leaves. The plant is also toxic at all times of the year, even in winter. This is one reason why it's important to be able to identify it by more than just the appearance of its leaves: Otherwise, you might not know that the now leafless plant in front of you is poison ivy, and if you accidentally touch it, you could develop a skin irritation. Making contact with urushiol even on dead poison ivy plants (or urushiol that has rubbed off onto walls, fences, etc.) can cause symptoms because the oily resin stays viable for five years.

It is not only touching this noxious weed that causes problems: ingesting the plant or touching an animal that has urushiol on its fur can also cause symptoms to develop.

Eating any part of a poison ivy plant can cause a rash to develop in your digestive tract. No one should ever ingest this plant but be especially careful when children are present to make sure they don't accidentally eat it If an animal eats poison ivy, consequences are less severe. Dogs and cats who eat poison ivy can experience gastrointestinal upset. Many species of wildlife can eat poison ivy without being adversely affected

Warning

Never burn poison ivy. Inhaling the smoke can cause a rash to develop on the lining of your lungs.

While dogs and cats can be affected with symptoms, they're less likely to because they are usually protected from direct skin contact by their fur. A related issue is that, while the poison ivy rash itself is not contagious, any object that comes in contact with urushiol becomes contaminated. This means that if your dog brushes up against poison ivy, and then you pet your dog, the urushiol is transferred onto your hand, and you can develop a rash.

Gardening Considerations

Poison ivy could be invasive where it's a non-native plant, but it is aggressive even where it is native. Poison Ivy can spread quickly, so if you find it growing anywhere on your property, take proper precautions to remove it.

Botanical Name Toxicodendron radicans
Common Name Poison ivy
Native Area Eastern United States and Southern Canada
Plant Type Deciduous, woody plant; can take the form of a shrub, climbing vine, or creeping vine
Mature Size Woody shrubs are one to two feet tall and wide. Mature vines can climb 50 feet or more up a tree and develop a 6-inch diameter
Bloom Time Late spring
Flower Color Off-white
USDA Hardiness Zone 4 through 10
poison ivy leaf trio
​The Spruce / Ana Cadena
poison ivy on a tree trunk
​The Spruce / Ana Cadena

Identifying Poison Ivy

Poison ivy's leaf is famously composed of three leaflets. But it's smart to learn about other ways to identify it (so that you don't accidentally touch it after it has dropped its leaves in winter) and how its appearance changes over time. Besides its distinctive foliage, poison ivy has:

  • Small, off-white flowers in spring
  • White berries in late summer that persist through winter
  • "Hairy" vines (on older plants)

How Poison Ivy Changes in the Course of a Year

The most obvious way in which poison ivy's appearance changes from season to season is its foliage:

  • Spring: various shades of red or orange
  • Summer: green
  • Fall: red, orange, or yellow (quite spectacular in some cases, as is also true of Toxicodendron vernix, known commonly as "poison sumac")
  • Winter: none, because the leaves will have dropped off by this time
Image of young leaves of poison ivy.
The Spruce / David Beaulieu
Poison Ivy
NoDerog / Getty Images
mature poison ivy
Bill Tanneberger

Where It's Found

Poison ivy is native to the eastern United States and eastern Canada; therefore, by definition, it can't be considered invasive there, even though it spreads aggressively even in that region. But it could be invasive in regions to which it has been introduced. Poison ivy is not fussy about sun and soil conditions, which is one reason why it is such a successful weed.

How to Remove Poison Ivy

Poison ivy should be removed from your property so that you don't accidentally make contact with it while gardening. It is possible to safely eradicate poison ivy, whether organically (manually) or with herbicides, but you must take extreme precautions and it might take several attempts. When working around poison ivy, it's especially important to wear gloves (wash the gloves and your clothes separately afterward from your other laundry) so that any residue you came in contact with isn’t transmitted to your food, your face, your pets, other people, or any other surfaces.

Article Sources
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  1. Identifying Poison Ivy. University of Maryland Extension