by Dr. Sarah Treanor Bois, PhD
Director of Research & Conservation at the Linda Loring Nature Foundation
As June settles into true summer, the flora of Nantucket really comes alive. The beach roses scent the air along the dunes, our yellow thistles open for pollinators, and the golden heathers carpet the moors. This past week, while enjoying the early summer splendor, another blossom caught my eye: small clusters of whitish-green, each flower only ¼-inch in size. The delicate five-petal flowers aren’t showy or brightly colored, but they are pleasant, gently draping in small clusters. These flowers, however, aren’t the kind to put in an arrangement or bouquet. These deadly beauties actually belong to the poison ivy plant.
Poison ivy, Toxicodendron radicans, is a native woody plant prevalent across Nantucket Island. The old adage “leaves of three, let it be” is a good thing to remember for identifying the plant. While other innocuous native plants have clusters of three leaves, it may be best to avoid all “leaves of three” if you’re not sure. Unlike some plants in the blackberry family with three leaves, poison ivy does not have thorns and generally has smooth leaf edges, though sometimes it is “variable toothed.” That basically means it does what it wants when it wants.
As the name implies, it is “toxic” or “poisonous” to the touch for many of the public—85% of people report they are allergic to poison ivy, but they are actually allergic to urushiol, the rash-causing oil produced by the plant. I am personally jealous of the other 15%. I am so allergic to it that I have learned to pay special attention to its habits—the various morphs it exhibits, habitat niches it likes to occupy, and its overall seasonality. One winter, when I thought I was free of it, I failed to wear gloves while digging up some invasive plants. I learned my lesson that “evil never sleeps.” Little did I know that the poison ivy roots lurked in the soil, too, and I ended up with very swollen fingers. Apparently, all parts of the poison ivy plant can produce urushiol.
Poison ivy is a plant I love to hate and hate to love. Instead of continually cursing the plant for my allergy, I am working on my poison ivy appreciation, for this native plant is an important part of our native flora.
I marvel at its ability to morph into many plant forms. As a woody vine, it climbs and encircles trees, as can be seen along the edge of the Nantucket State Forest. It can appear herbaceous, growing among the low bush blueberries and wildflowers at the edge of paths. Each stem seems to know how tall to grow to mimic the surrounding plants. It can be shrubby in nature, growing in and among the bayberries and huckleberries and growing no more than hip height. Making sure to cover all of its bases, I have even seen poison ivy looking like a tree, though this has been exclusively in marshes.
While I hate to admit it, there are more reasons to admire this shape-shifter. In addition to being a master of disguise, poison ivy may be the super plant of the future. Researchers have found that poison ivy responds extremely well to elevated CO2 levels as predicted with future climate change. You think that would be the case for all plants with more CO2. However, poison ivy has been shown to be more adept at reacting quickly to excess CO2, growing 149 percent faster than poison ivy grown without elevated CO2. These elevated carbon dioxide levels are creating bigger, stronger poison ivy plants that produce more urushiol. The urushiol isn’t just more plentiful, it was also more potent. Great!
There has also been some research, though limited, on the phenology, or timing, of poison ivy leaf-out and flowering. In our region, poison ivy may be leafing out earlier, meaning that the poison ivy is around longer in the year, so there is more opportunity for exposure.
Poison ivy fruits are plentiful in late summer and early fall. Birds love the poison ivy berry, which is high in lipids, providing much needed fat calories for fall migration. These berries are also an important food source for other wildlife like white-tailed deer. Deer will even graze on the twigs and leaves. Lucky for them that deer, birds, and other Nantucket fauna (including dogs) are not allergic to the urushiol oil.
And if all of this wasn’t enough, poison ivy can be really useful for restoration projects and can be considered a nature-based tool for erosion control. It is considered an early successional plant, meaning it often grows in disturbed areas and can help stabilize soil and provide cover for other plants to establish. It thrives in disturbed landscapes, places where not many things will grow. You can see it near beaches, which are constantly getting beaten by coastal storms. You’ll see it along roadsides or abandoned lots, which are disturbed by other forces. In a few of our restoration spots at the Linda Loring Nature Foundation, poison ivy was the first native plant to colonize a disturbed site after removing non-native invasive species. Removing my own bias, this plant is considered a success given the other ecosystem services it provides.
It’s hard for me not to admire a plant like Poison Ivy, even if we have a lovehate relationship. It can seemingly shape-shift to blend in with its surroundings in a way that other plants cannot. It has the ability to colonize disturbed areas and be a pioneer species stabilizing soil and re-vegetating barren areas. And it is one of the few plants that can capitalize on the mess we’ve made with climate change. Poison Ivy can grow earlier, bigger, taller, and stronger in light of elevated CO2 and increased temperatures. So, if we’re mad about it, it’s our own fault.
We’ve created a monster.
