By BreyAn Witt
The Nature Academy is focused on training a new generation of environmental leaders in sustainability, conservation, and ecological restoration. As part of the Nature Academy program, each intern writes a blog post and develops a project. The project provides an opportunity to take on responsibility in an area of interest, contribute to the goals of their team, and develop a skill or area of knowledge that can be added to the intern’s portfolio. The post may reflect the project or be a nature-related topic of personal interest to the intern.
Many of us are familiar with the saying “leaves of three, leave it be” as a memory device for identifying poison ivy. I’m used to seeing poison ivy growing on the ground but not on trees. During a woody plants course at University of Michigan-Flint I was introduced to poison ivy (Toxicodendron radicans) growing on trees but it didn’t have any leaves on it because it was late fall.
When I started my internship at Matthaei Botanical Gardens and Nichols Arboretum this summer I was told to watch out for poison ivy at all locations. My internship involves taking measurements, assessing the health of trees, and database management of woody plants. I thought I knew what poison ivy looked like. I started assessing trees at Nichols Arboretum, and I was seeing a lot of poison ivy everywhere. To my surprise, most of what I was seeing was not poison ivy but Virginia creeper (Parthenocissus quinquefolia), which I had never heard of before.
I began researching the differences between the two plants. First, I took pictures of Virginia creeper and then looked in the field guide I was given, Michigan Shrubs & Vines by B. Barnes, C. Dick, and M. Gunn. I used the Missouri Botanical Garden’s Plant Finder website and michiganflora.net (a website administered by the University of Michigan Herbarium, part of the university’s College of Literature, Science, and the Arts).
Some key characteristics of Virginia creeper are aerial roots; palmately compound leaves with five leaflets radiating from a central point, tendrils with small sticky disks that grasp tree trunks, and blue to bluish-black berries high in the canopy. Palmately compound means that the five leaflets are considered as one leaf. Another species common throughout Michigan and similar to Virginia creeper is called thicket creeper (Parthenocissus inserta). The difference between the two species is the way they climb trees: Virginia creeper has tendrils with sticky pads while thicket creeper has tendrils with twining tips.
The key characteristics of poison ivy are aerial roots; three leaflets with the middle leaflet having a longer stem; drupes (fleshy fruit with a seed inside) that are white during the fall and winter; and a growth form as a creeping vine, climbing vine, or a low shrub. Its leaves are considered pinnately compound, which means that the 3 leaflets are considered as one leaf. When I was taught about poison ivy, the leaves reminded me of mittens, with the middle leaflet sometimes appearing as a double mitten. The mitten pertains to the shape of the leaves because they look like they have thumbs. Another good saying about poison ivy is “a hairy vine, a danger sign.” Danger because the oil of poison ivy, known as urushiol, can cause dermatitis. Urushiol is present in all parts of the plant, including roots and stems.
Did You Know?
Poison ivy is part of the Anacardiaceae family, which includes cashews, mangoes, and sumacs. Several species of sumac can be seen along the sides of highways. The most common ones are smooth sumac (Rhus glabra), staghorn sumac (R. typhina), and winged sumac (R. copallinum). Not all members of the Anacardiaceae family are toxic but the family does include poison oak (T. diversilobum) and poison sumac (T. vernix). Anacardiaceae can be called the cashew family or the sumac family. It includes 83 genera.
Staghorn sumac growing along the Alex Dow Field in Nichols Arboretum. Sumac is in the Anacardiaceae family, to which poison ivy belongs.
The yellow cashew apple with the nut hanging below. Photo by Steven dosRemedios. The cashew is in the Anacardiaceae family, to which poison ivy belongs.
There are other differences between Virginia creeper and poison ivy. Leaflet number is a big one but sometimes when they are starting to grow or leaf out the coloring and leaf quantity look similar with a slight red hue. Once both of them are more mature, it is easier to tell the difference between Virginia creeper and poison ivy. Winter also helps with identification because you can clearly see the tendrils or aerial roots.
The leaves of poison ivy may look different from plant to plant or even on the same plant, and its three forms—vine, low-lying plant, and a kind of shrub—can make ID challenging. The vine form can be found growing on trees, buildings, and abandoned objects. These three pictures show how different leaves can look from plant to plant. The first plant is the textbook picture (The Spruce website). The second plant is a dull green with a little yellow (Chicago Tribune) while the third example looks red and waxy (Healthline).
Some people confuse poison ivy and wild red raspberry (Rubus idaeus). Several of my family members have asked me if they have poison ivy or raspberries on their property. Wild red raspberries have three coarse serrated leaves which are similar to poison ivy. Raspberries are upright shrubs with arching branches. With raspberries, leaves can be in quantities of three to five. Raspberries have glandular prickles that are underneath bristly hairs. The mature stems of the raspberry are red to pink in color. If I were you, I would let the plant be until it matures a little more to see if it has the prickles and hairs along the stem.
My hope is that this brief guide will help with identifying poison ivy and distinguishing it from similar-looking plants such as Virginia creeper. The best thing to do is get out in the field, dress appropriately for the weather and the site, bring a field guide or two, take pictures, and practice your ID skills.
BreyAn Witt has a bachelor’s in wildlife biology with a GIS certificate from University of Michigan-Flint. She is currently working on a practicum in conservation ecology at the U-M School of Environment and Sustainability. BreyAn is from Swartz Creek, Mich., and enjoys reading, camping, and hiking.