Lora Conrad lives on a small farm in Van Buren County.

Poison Ivy (Toxicodendron radicans) is a plant anyone in Iowa should learn to identify. Most of us have heard stories about it, seen it (or thought we did), and many have experienced it.

Poison ivy is also the topic of many folk sayings—some helpful, some not, some just confusing. This article will help you learn how to identify this plant, what its effects are, and which of those many sayings are accurate.

HOW TO IDENTIFY POISON IVY

The genus Toxicodendron includes Poison Ivy—both Eastern (Toxicodendron radicans) and Western (T. rydbergii), as well as Poison Oak and Poison Sumac. Poison Ivy was originally placed in the genus Rhus (the Sumacs) but by the 1930s, botanists began separating the irritating plants from the other Sumacs. They were assigned to the genus Toxicodendron which is Greek for “poison tree.” Both species of Poison Ivy occur in Iowa. T. radicans is the familiar trailing or climbing vine that is called Eastern Poison Ivy. It is widespread throughout Iowa. You can see why it is called a poison tree:

T. rydbergii or Western Poison Ivy is the non-climbing Poison Ivy that is a shrub or sprout. It has been documented in over 20 of the most northern counties and a few other locations, including Van Buren. The early sprout will be just a couple of leaves close to the ground.

Then it will be a larger plant or shrub.

Here are some images to help you identify Poison Ivy when in the woods, the yard, the park or by the roadside. It grows almost anywhere it gets an opportunity. The (usual) three leaves of poison ivy all have pointed tips with leaf edges that may be either serrated or smooth. The leaves typically look smooth and glossy.

Yet almost nothing is “always!” It is highly variable in the way it looks, which makes certain identification an uneasy thing until you have looked at a lot of it.

First, a vine growing in June.

Here are the green berries in July:

The green vine has cream colored berries by September.

By October the berries are more golden.

Late in October, you will see the fall colors in the leaves.

The vine will show up more by late October if it is Eastern Poison Ivy.

FACT-CHECKING THE FOLK SAYINGS AND BELIEFS ABOUT IDENTIFICATION

“Leaves of three-let it be.” Confusing.

Poison Ivy does have “leaves of three”—well, mostly! A research project at Virginia Tech found Poison Ivy plants with five leaves that came in both pinnate (opposite) and alternate leaves! The “typical” leaves of three.

Yet, there are many other plants with “leaves of three.” In Iowa, these include all of the following plants. First, Beans—members of the Phaseolus genus in the Fabaceae or Leguminosae family.

Box Elder (Acer negundo) seedlings have leaves with three leaflets and can look like Poison Ivy at first glance. However, Box Elder leaves grow opposite each other along the stem; Poison Ivy leaves usually grow alternately along the stem.

Fragrant Sumac also has leaves of three—here in fall colors similar to those of Poison Ivy.

Hog Peanut (Amphicarpaea bracteata), the ever present late summer and fall vine of Southeast Iowa woodlands also has leaves of three:

The young Jack-in-the-pulpit (Arisaema triphyllum) is another leaves of three in Iowa spring woodlands.

Wild Raspberry leaves in Iowa woodlands also carry the same leaves of three pattern including the irregular and sometimes sharp cut on the outside edge, though they look a little fatter.

The young Tick Trefoils (Desmodium sp.) have leaves of three, though they are slimmer than Poison Ivy, usually.

All the Trillium species have leaves of three. However, many of these have a splotch pattern that is not seen in Poison Ivy. They also tend to be smooth edged and rounder.

There are other “leaves of three” that occur in Iowa that I do not have photos for illustration. These include Mock Strawberry (Potentilla indica) and Wild Sarsaparilla. While young Mock Strawberry leaves are similar size and shape, they connect to the stem at one central point. This contrasts with Poison Ivy leaves, which are usually opposite with the terminal leaflet on a longer stem stalk.

Minnesota Wildflower states:

The early leaves of Wild Sarsaparilla are often a shiny, bronzy color that looks rather similar to early Poison Ivy (Toxicodendron rydbergii) leaves, which emerge about the same time. Wild Sarsaparilla often has more than 3 leaflets and its flower buds, which don’t resemble Poison Ivy at all, will be out with the emerging leaves. The leaflet shape of mature plants doesn’t much resemble those of Poison Ivy. Wild Sarsaparilla leaflets are finely serrated whereas Poison Ivy leaves are smooth or coarsely toothed.

Virginia Creeper (Parthenocissus quinquefolia) is often mistaken for it even though there are usually five leaflets in each leaf. The catch is there are sometimes three as I find often in Van Buren County on Virginia Creeper.

Or you see the two growing right together, as shown here.

And when you add the leaflet number confusion to the Virginia Creeper vine running up the tree beside a large and hairy Poison Ivy vine—well—just look.

“Longer middle stem, don’t touch them.” Confusing.

Poison ivy has a longer stem at the base of the middle leaflet. As a result, the middle leaflet extends farther out from the leaflet stem than the two side leaflets. While this is true, it is subtle enough to leave many undecided when observing and is insufficient as there are other plants in Iowa where the middle leaflet sticks out further than the other two. The photos above for beans, hog peanut, and raspberry all illustrate this.

“Hairy vine, no friend of mine.” Confusing.

Larger Poison Ivy vines have many small tendrils or hairs that the plant uses to adhere to whatever it’s climbing. Note though that younger vines do not have such tendrils.

Other climbing woody vines in Iowa such as Wild Grapes, Trumpet Vine, Bittersweet, Wild Clematis have smooth vines, making the distinction easy. This is a reliable indicator for vining Poison Ivy—with one exception. Virginia Creeper has tendrils on the more mature vines. However, these are short rootlets with little suction cups on the end, but it still looks similar.

Remember: most, but not all Virginia Creeper leaves will have five leaflets. Some will have only three, as noted above! Thus making this one of the plants most often mistaken for Poison Ivy. See this Virginia Creeper vine.

Often people encounter Poison Ivy in Iowa through young sprouts or low bushes with no hairy tendrils.

POSSIBLE EFFECTS OF EXPOSURE

What causes the rash?

The chemical that causes an allergic reaction in humans is a sticky, pale yellow oil named urushiol (yur-oo-shee-aal). A Japanese scientist identified it in the 1920s and determined how it worked. Urushiol is found in all parts of the Poison Ivy plant—the leaves, stem, vines, flowers, and roots.

Strangely, urushiol is not poisonous. When it is absorbed through our skin, oxygen activates an alkyl chain that is part of the molecule. It then combines with skin proteins. These urushiol-studded proteins are recognized as invaders by our body’s immune system. This causes the painful rash, blisters and itching as it fights the invader—an allergic reaction. The whole process takes place if urushiol is allowed to remain on the skin for a short time—as little as five minutes for some people and up to 20 minutes before it begins the process. Within 8 hours it is completely bound.

What to do if exposed

If you accidentally touch Poison Ivy, bathe the skin with alcohol and then rinse the exposed area with water (if no alcohol, then bathe the skin with cool water.) Preferably do this within five minutes of exposure, but no matter how much later, clean this way. Washing becomes less effective as the time passes. If you use soap, use Dawn dish soap or something similar which cuts oil. (Soap used, if any, should not have any oil in it as oil only spreads the urushiol.)

Who reacts to the urushiol?

Most people—estimated to be between 70 percent and 85 percent—are allergic to the urushiol in Poison Ivy. I can personally assure you that there is plenty in the roots. The worst case I ever contracted was planting bulbs in late fall in the edge of woods after all the leaves had fallen—I was digging through the roots without realizing it for more than an hour. Touching it exposes you but if plant parts are crushed or damaged, then additional oil is released.

Not everyone is allergic to these plants, and sensitivity varies between people, but allergies to it often develop with increased contact. So you may not be allergic to it—until you are. Always assume you might be allergic to it this time. The American Academy of Dermatology states:

The amount of time it takes for a rash to appear depends on whether you’ve had a rash from one of the plants before. Here’s the general rule:

• Previous rash from Poison Ivy, oak, or sumac: A rash usually appears within 4 to 48 hours.
• Never had a rash from Poison Ivy, oak, or sumac: It typically takes 2 to 3 weeks.

A cautionary tale

Touching the plant isn’t the only way urushiol spreads. Urushiol can transfer from the plant to something that a person then touches. Touching the fur of a pet animal that has brushed against some Poison Ivy can transmit urushiol to you. Picking up your own or somebody else’s gardening gloves or other tools after working in Poison Ivy can cause a rash. Handling shoelaces or other clothing parts that have touched the Poison Ivy can transmit it to hands—then if you rub your eyes or touch another part of your anatomy—time will tell.

Urushiol can remain on clothing/fabric for up to 10 years! That’s right—urushiol on your jeans, your boots, your camping gear can give you the rash years later, if these things have not been well washed.

Special note: NEVER BURN POISON IVY! Fire does not destroy it but releases urushiol into the air. Breathing it in could send one to the hospital.

FACT CHECKING FOLK SAYINGS AND BELIEFS ABOUT THE POISON IVY RASH

“Poison ivy spreads from scratching.” False.

Some parts of the body react faster than other parts to the urushiol oil. Once the oil has been washed off your skin, the rash cannot spread to other parts of your body or to other people. New rashes mean you were exposed to the oil at those locations but it took longer to show up.

“It is contagious from the blister fluid.” False.

Once the oil has been washed off, you cannot give the rash to anyone else. It is only the oil that causes the rash, not the fluid from blisters.

“You can’t get Poison Ivy from a dead plant.” False.

The oil can be retained on/in dried plants for several years and still give you a rash.

“Use crushed Jewelweed to stop Poison Ivy rash.” True.

Research found: “Jewelweed mash was effective in reducing Poison Ivy dermatitis, supporting ethnobotanical use. However, jewelweed extracts were not effective; and soaps made of these extracts were effective but no more so than jewelweed-free soaps.” Jewelweed is often growing in damper areas where Poison Ivy may also be growing.

VALUE TO WILDLIFE

This excerpt from Georgia Wildlife sums up the plant’s value to wildlife.

As unsavory as Poison Ivy is to humans, it is a great source of food for a host of our wildlife neighbors. Yes, these animals show no allergic reaction to the plant even when they devour its berries, leaves and stems.

The list of mammals that dine on Poison Ivy include white-tailed deer, black bears, wood rats and muskrats. Birds are especially fond of Poison Ivy berries. The plant’s waxy, white berries are loaded with vitamins and other nutrients. If that isn’t enough, they are available to south-bound migrants in mid-summer as well as in winter when food is at a premium.

The long list of birds that relish Poison Ivy includes bobwhite quail, brown thrashers, northern mockingbirds, red-headed, downy, hairy, pileated and red-bellied woodpeckers, yellow-bellied sapsuckers, northern flickers, yellow-rumped warblers, Carolina chickadees, blue grosbeaks, eastern bluebirds and gray catbirds.”

HOW TO GET RID OF POISON IVY

Though it is a native plant, it is not a safe plant to have in your yard or garden. So if you need to get rid of it, The Spruce has an article about numerous possible options to use including spraying.

IN POP CULTURE

Enshrined in song by the Coasters in a 1959 hit, “Poison Ivy” is cute and catchy and perhaps euphemistic. Here is part of the text of the song.

……………………
Measles’ make you mumpy and mumps’ will make you lumpy,
And Chicken pox will make you jump and twitch.
The common cold will fool you,
And whooping cough will cool you.
But Poison Ivy Lord will make you itch!

Your gonna need an ocean,
Of calamine lotion.
You’ll be scratchin’ like a hound,
The minute you start to mess around!

Poison Ivy,
Poison Ivy,
Late at night while your sleepin’,
Poison Ivy comes creepin’ around.

To get the full effect, watch The Coasters perform the song.

FICTIONAL CHARACTER

Poison Ivy is a fictional super-villain/anti-heroine first appearing in DC comics and also featured in TV, film and video games. She is one of Batman’s enduring enemies. You may have seen one of her incarnations and/or some of the thousands of art work pieces of her online. If not, here is one.

CONCLUSION

This article was intended to give you a bit of new knowledge, some “food for thought” and a smile or two about Poison Ivy. If you want still more info about it, check out the list of references.

References
https://georgiawildlife.com/out-my-backdoor-wildlife-food-plant-we-love-hate

https://www.outdoors.org/resources/amc-outdoors/outdoor-resources/how-to-recognize-and-avoid-poison-ivy-three-sayings-to-remember/

https://extension.umd.edu/resource/how-identify-poison-ivy/

https://www.dmuclinic.org/health-topics/posts/everything-you-need-to-know-about-poison-ivy/

https://www.mayoclinic.org/diseases-conditions/poison-ivy/symptoms-causes/syc-20376485

https://www.aad.org/public/everyday-care/itchy-skin/poison-ivy/what-rash-looks-like

https://www.aad.org/public/everyday-care/itchy-skin/poison-ivy/who-gets-contagious

https://www.aad.org/public/everyday-care/itchy-skin/poison-ivy/treat-rash

https://pubmed.ncbi.nlm.nih.gov/28087871/

https://cdn-uat.mdedge.com/files/s3fs-public/JFP06511801.PDF

https://www.sciencehistory.org/stories/magazine/no-ill-nature-the-surprising-history-and-science-of-poison-ivy-and-its-relatives/

https://www.streetdirectory.com/lyricadvisor/song/jlpfp/posion_ivy/

https://news.vt.edu/articles/2024/03/cals-research-poison-ivy.html#:~:text=We%27ve%20all%20heard%20the,harmless%20three%2Dleaf%20native%20plants.

https://pubmed.ncbi.nlm.nih.gov/22766473/