Before we answer the poison oak question, let me set the scene…
As I type this, I have both forearms coated in the candy-pink of dried calamine lotion. Drops of the stuff have followed me around my house, plopping on the bathroom sink, our kitchen’s vinyl floor, my steering wheel, and even on the aluminum case of my computer.
Bathing my arms in calamine lotion hourly seems the only way to keep the maddening itch of urushiol-induced contact dermatitis at bay. If you’ve crossed paths with the oily evil of poison ivy, oak, or sumac, you know that itch. It feels like an army of baby ants, chewing through my skin with sharp, tiny mandibles…
Crap, this is not helping. More calamine.
Where’d it come from? My best guess is that I splattered open some poison ivy while weed trimming a fence line last week. That’s exactly what the rash looks like. If you don’t have experience with weed trimming, just know that thick clumps of weeds don’t die quietly, especially if you use plastic brush blades. Weeds rupture in a spray of watery weed guts and coat your arms, pants, and wrist watch. My rash is their dying revenge.
I’ve had hospital-level reactions to poison icy before, although I had managed to avoid it for more than two decades. Those earlier instances—one so bad that my face swelled into a Twilight Zone nightmare for a week—have made me watchful. When this bout started up, I didn’t screw around. I went right to the doctor, gave them the rundown, got some steroids, some Zyrtec, and bought a whole lotta calamine.
So far, I think it won’t be so bad. Some swelling. One eye shut a little until I got an ice pack on it. I’ll get through all right, as long as I don’t scratch.
I posted a public service reminder on our Facebook page the next day, including a chart of the three most common poisonous plants: poison ivy, poison oak, and poison sumac. Most responses offered sympathy and homemade remedies.
The comments debating the existence of poison oak in Indiana received the most attention. These discussions turned into debates and some turned downright ugly, with insults splattering the post like, well, like weed guts. Some were ferocious enough to delete. I’ve moderated our page daily for over three years, and I usually can predict which posts will cause a stir and which will not. This one surprised me.
What is it about poison oak that gets Hoosiers riled up?
What’s in a name?
Part of the confusion may stem from the common versus scientific name of poison oak. The scientific name of “poison oak” is the genus Toxicodendron Mill, and there are seven species recognized in this genus: Pacific poison oak, Atlantic poison oak, eastern poison ivy, western poison ivy, wax tree, Chinese lacquer, and poison sumac.
That is pretty damn confusing, I know.
What all that means is that all of those are technically poison oak. When scientists, botanists, biology departments, and conservation groups say “There is no poison oak in Indiana” are they talking about the species (Pacific and Atlantic poison oak) or the entire genus? According to the USDA, they are referring to the species. Or are they?
Check out these maps. 
USDA gives you fresh food, but stale info…
Now this information is presented to the American public by the National Resource Conservation Division of the United States Department of Agriculture. These are the people that determine if our water is safe to drink, if our soil is safe for planting, and partially regulates American farmers. In a nutshell, these 11,000 people watch over the food you put in your kids’ bellies for breakfast.
With all that expertise, this department’s information on one of the common allergens in the United States—which affects around 50 million Americans annually—is more confusing than stereo instructions. Browse their database for yourself HERE. You’ll see what I mean.
A tiny bit of print tucked into a corner of the maps concerned me even more than the poorly-presented data…
To be fair, I am not sure if that date refers to the maps, to the data base, or to the plug-in that powers the interactive maps. It could be the plug-in.
However, if you want your audience to know you are adding fresh content (or data) to a page, the copyright needs to reflect that. Look at the footer for this very article, and you’ll notice the copyright covers 2017 to 2021, primarily to let readers know the site’s contents are not staler than decade-old Saltines.
2014? Yikes.
It’s not just the USDA…
There’s an article from the Indy Star in 2017 that insists “…poison oak (Toxicodendron diversilobum) is rarely found outside the western United States” and “There is Atlantic poison oak (T. pubescens), a native vine or shrub-like plant. Although uncommon, it is found in Illinois and states south and east, but not in Indiana.”
I also found this informational pdf from Purdue University on Consumer Horticulture is even more confusing. The pdf whispers in a very tiny font that its contents were adapted with permission from another source, but I read both. Adapted is one word. Copy-and-pasted is a more appropriate one. Both said this:
“People often use the names “poison ivy” and “poison oak” interchangeably; this is incorrect. Poison ivy is the only species found throughout Indiana. Poison oak (Rhus toxicodendron), is a low-growing, non-climbing shrub, that is not known to occur in Indiana…”
~”Poison Ivy” Consumer Horticulture, 2015
This confusion becomes downright irritating. The USDA said poison ivy is a species of poison oak, and that there are in fact TWO kinds of poison oaks, but several botany departments and a professional gardener says otherwise. That’s [Insert your favorite swear word here].
The most intelligent response I found…
This article is not a diatribe against academic science or higher institutions of learning. However, when answers are evasive and muddled, Americans can get frustrated and sometimes lose trust in these resources. We want a clear answer. It can be a yes. It can be a no. It can even be “we don’t know.” There’s nothing wrong with admitting honest ignorance. When answers are diced and chopped into a confusing hash, practical Americans have a hard time swallowing them.
But look what I found.
It’s an older source, from July of 2007, but it’s as honest as you’d want. A Mr. Glenn Nice, who received a Masters in Weed Science from Mississippi State University, spent a decade working at Purdue University (2001-2011), designing and maintaining the university’s Weed Science extension program. Mr. Nice’s knowledge comes from a mixture of classroom science and down-in-the-dirt field work.
In his 2007 informational packet, appropriately titled “The Don’t Touch Me Plants,” Mr. Nice had this to say about the poison-oak-in-Indiana controversy:
“According to the USDA plant database, poison oak has not been reported in Indiana as of yet, but it has been reported in Illinois. However, although the USDA has not officially confirmed poison oak in Indiana, I have received word-of-mouth reports that it is present.”
~Glenn Nice, 2007. Purdue University
Clear, concise, and exactly correct.
Eyes on a screen vs. eyes on the ground
When I began moderating the arguments on the “poison oak post,” I was ready with pdf links to demonstrate that poison oak cannot possibly exist in Indiana. Having Purdue back you up is persuasive.
But when I see a half-dozen people tell me they not only have seen it, but it’s on their own property, I’m practical enough to listen. Here are a few…
The final answer…
Do we have poison oak in Indiana? Yep, we do. It might not be native, and ivy and sumac are likely much more common, but it here’s. I, personally, have not seen poison oak, but then again I’m terrible at identifying plants. Next time I’m near the woods, I am going to keep an eye out for it. If I find some, I’ll snap a picture.
For right now, I’m keeping my distance. One rash at a time.
Want to Know More?
Here’s a direct link to Glenn Nice’s informational packet “The Don’t Touch Me Plants” from the Purdue University Weed Science Extension. It’s dated 2007, but it offers clear explanations and practical advice. Plus, it’s written by a fellow who has been in the field and knows when to trust his eyes and ears more than a lecture hall.
