Many who venture outside live and die by the general rule-of-thumb, “Leaves of three, let it be.” This motto comes in context of avoiding the ever-so infamous poison ivy plant. A majority of people stay clear of its treacherous tendrils as it is known to cause skin irritations brought forth by an oily substance the plant produces called urushiol. Approximately 85% of the U.S. population is allergic to poison ivy, as well as poison sumac or oak, making it one of the most common allergic reactions (American Skin Association, 2020). Sensitivity to poison ivy can vary from person to person, and those who do not react initially may develop a sensitivity to urushiol oil overtime. Sounds like poison ivy has a bit of a bad reputation built up, but is there any chance this plant has been framed in the wrong light? There just might be some benefits unbeknownst to us that could bring justice to poison ivy’s thorough presence.
Poison ivy image taken by Cam Mannino.
I am one of the few lucky individuals who (thus far) has had no reaction to poison ivy. I can recall spending time in forests as a child and being warned about the poison ivy that may be lingering near the trails, so I was always sure to avoid it. However, I remember freaking out in college as I traipsed through woods carpeted with poison ivy for my ecology course, which is where I first learned that I am unreactive to it. I have come to understand that this is a seemingly rare fortune, and I surely am glad to have it as I have heard the horror stories of reactions some have. In fact, Bianca and Matt (our other land stewards) have had their fair share of negative encounters – Bianca has the scars on her knee to prove it!
Even during the last Wednesday morning bird walk I attended, I couldn’t help but to listen in on some of the attendees’ conversations regarding this hazardous plant. Multiple people mentioned their disdain for poison ivy and even wished for ways to eradicate it from their yards completely. This got me thinking about why poison ivy is so prevalent, and why other animals are not impacted by its precarious oil. Surely there had to be some ecological benefits to its presence.
Both Eastern and Western species of poison ivy are native to Michigan, but we are more likely to see Eastern poison ivy (Toxicodendron radicans) in the southern Lower Peninsula (Hill & Tenney, 2020). Eastern poison ivy grows as a vine with aerial roots, while Western poison ivy grows upright and does not climb or have aerial roots (Hill & Tenney, 2020). In general, poison ivy can be somewhat easily identified by its signature compound leaves with three leaflets, and the stalk of the middle leaflet is almost always longer than the two on the sides. Additionally, the side leaves have large teeth on their outer edge, which are often said to resemble a thumb. While this native, woody shrub causes some of us redness, itching, swelling, and blisters, I learned that it provides an important food and shelter source for many critters. Many birds, mammals, reptiles, and amphibians feed on the leaves and the fruit of poison ivy plants, called drupes (Mathes, 2019).
Image of fruiting poison ivy provided by Garden Gate.
But this still did not answer my question as to why these animals are able to frolic through and consume poison ivy – why must humans be the only ones doomed to itch? The simple answer is that humans do not have the same protective coat, such as fur or scales, that these other animals do. Ok – makes sense – but how can they possibly CONSUME this plant? While I’m still searching for a perfect answer, one blog notes that deer are often able to survive eating poisonous plants by consuming toxin-neutralizing compounds, such as clay soils or salt licks, directly after eating the poison (For Fox Sake Wildlife Rescue, 2020). So, in a way, these animals are able to consume poison ivy in the same way I am able to consume spicy foods – they neutralize the poison with clay and salt, while I neutralize the spice with milk and peanut butter (it works, I promise).
Regardless, knowing the benefits poison ivy brings to some of my favorite wildlife, including Eastern cottontail rabbits and White-tailed deer, I have a newfound appreciation for this otherwise burdensome plant. And even if you cannot quite appreciate or forgive poison ivy for its cruel oil, I hope we all can learn to tolerate its presence for the benefit of our wildlife. So, next time you angrily wish away plants that appear perilous to you, I challenge you to check out some of their benefits and spread the word of their good!
References:
Deer Can Eat Poisonous Plants. (2020). For Fox Sake Wildlife Rescue. Accessed online June 29, 2023 from https://forfoxsakewildlife.com/2020/12/19/deer-can-eat-poisonous-plants/
Hill, E. & Tenney, A. (2020). Poison Ivy in Michigan. Michigan State University Department of Plant, Soil, and Microbiology. Accessed online June 28, 2023 from https://www.canr.msu.edu/pestid/resources/plant-and-weed-identification/PoisonIvy_E3438_AA%20(002).pdf
Mathes, H. (2019). Poison ivy is the wildlife salad bar of the woods. Tallahassee Democrat. Accessed online June 28, 2023 from http://www.tallahassee.com/story/life/home-garden/2019/10/24/poison-ivy-wildlife-salad-bar-woods/4076245002/
Poison Ivy, Sumac, and Oak. (2020). American Skin Association. Accessed online June 28, 2023 from https://www.americanskin.org/resource/poisonivy.php
Very interesting as always, Cam! I did not know that some wildlife ate poison ivy. And like you, I have never had a reaction to it, and I hope it stays that way!