Everything you need to know about poison ivy (how to identify, avoid, treat, and kill it)

I don’t like this, and if you are outdoorsy at all, you won’t either!  According to some recent studies, the allergen in Toxicodendron (that is, poison ivy, poison oak, poison sumac, and some others) is getting stronger over time.

It seems that poison ivy, for some reason, is more sensitive to increased atmospheric CO2 than other woodland plants.  As CO2 levels rise in the atmosphere, not only do they cause a warming trend in the atmosphere, but they promote explosive growth of poison ivy and its irritating cousins.  And not only does it make the plants grow larger and spread faster, but it also causes them to produce more of the oily irritant urushiol.

Poison ivy is getting larger, more widespread, and more severely allergenic over time!

Here is part of the abstract from the 2006 study by Duke University scientists, Mohan et al. published in the Proceedings of the National Academy of Science.

…we show that elevated atmospheric CO(2) in an intact forest ecosystem increases photosynthesis, water use efficiency, growth, and population biomass of poison ivy. The CO(2) growth stimulation exceeds that of most other woody species. Furthermore, high-CO(2) plants produce a more allergenic form of urushiol. Our results indicate that Toxicodendron taxa will become more abundant and more “toxic” in the future, potentially affecting global forest dynamics and human health. (Proc Natl Acad Sci U S A. 2006 Jun 13;103(24):9086-9. Epub 2006 Jun 5. Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmosphericCO2. Mohan et al.)

More people these days are starting to figure out that they need to be more connected with nature because it’s good for you and because the more people become interested in the natural world, more competently we can deal with issues like plastic trash and climate change.

But one of the first things that you’re going to want to know how to deal with when you start getting more nature exposure is poison ivy – how to identify it, avoid it, and treat exposure to it.

Poison Ivy is a member of the Toxicodendron genus, which also includes similarly irritating plants like poison oak and poison sumac.


How to identify poison ivy

Leaves of three, Leave it be – This is a common mnemonic device to help you identify poison ivy and poison oak.  Basically, it is a good idea to avoid any low-growing or vining plant that has clusters of three leaves – especially if the leaves resemble oak or ivy leaves.

Problem with that is the plant is deciduous, meaning it loses its leaves in the wintertime.  When this happens you can still identify poison ivy because of the vines or berries.

Hairy vines are another distinctive feature of poison ivy (but not poison oak or sumac).  Poison ivy produces many aerial roots – so many that the vines look hairy, especially as they get older and larger.  If you see a hairy-looking vine growing up a tree, it may well be poison ivy.

Poison ivy produces white berries.  It is a good general rule of thumb that all white berries (like tallow tree and mistletoe) are poisonous – and that rule of thumb can help protect you from poison ivy in the fall and winter.


Poison ivy look-alikes

Virginia creeper (Parthenocissus quinquefolia) have leaves that look very much like poison ivy leaves, but they grow in clusters of five instead of three.  “Leaves of five, friend of Clive” (whoever Clive is).  But you still have to watch out because Virginia creeper tends to grow in the same environments as poison ivy, so there may very well be real poison ivy growing alongside and with Virginia creeper vines.  It is common to see leaves of three and leaves of five together.

Blackberry shoots, when very young, often have clusters of three leaves.  Even though Blackberry doesn’t have any urushiol in it, you probably still want to avoid it because of the vicious thorns.

Muscadine and wisteria can climb a tree similar to poison ivy, but the vines are not hairy.

How to kill poison ivy

Mowing is not recommended because you have to do it repeatedly, and it can spread the plant particles containing the irritant a long way.

Do not burn poison ivy to kill it.  Droplets of the urushiol can be spread in the smoke and may get in someone’s eyes, mouth, or throat.  Don’t use hairy vines to start a fire.

Glyphosate will kill poison ivy, but you have to be careful not to overspray and get the chemical on other plants or in the wind.  Large vines can be cut with bypass loppers and the cut ends painted with glyphosate to avoid spreading the herbicide in the wind.

The best way to get rid of poison ivy and poison oak is to stake goats out.  They’ll eat Toxicodendron down to the ground

How to treat exposure to poison ivy

If you are exposed, you probably have 20-30 minutes to wash it off with soap and cool water.  Don’t use hot water because it can cause your pores to open up and admit the oil.

If you develop a rash –

  • cover it so you don’t scratch it – even though the blisters do not contain urushiol and you will not spread the rash by scratching, you can get an infection or damage your skin by scratching.
  • Calamine or Benedryl might help,  We grew up perpetually painted pink from Caladryl lotion.
  • Hydrocortisone cream (a topical steroid) might help, and in severe cases, an MD might give you oral steroids
  • The best inexpensive, topical, OTC poison ivy treatment that the Roaming Parkers have found is Tecnu.  It is an oatmeal-based wash that seems to really knock out the oil and soothe inflamed skin.


Categories: Nature