Stories about the fascinating world of plants

By: Sam Hickman

Disclaimer: Sassafras tea made directly from sassafras roots contains the compound safrole, which has been classified as a carcinogen and banned from use in human food by the US FDA. Please consult a medical professional before attempting to consume sassafras tea.

Without even realizing it, I’ve used sassafras tea to make connections all throughout my life. It started when I was a kid, and my family would have holiday picnics at my great-grandma’s house, which was a lot of fun for us kids since we would always get to explore the woods behind the house. My cousins and I would run around looking for turtles and toads, and we would eat as many black raspberries as humanly possible and get our hands all scratched up from the thorns. We’d tire ourselves out, then come back to the house where our parents were waiting just beyond the sassafras trees.

On more than one occasion, one of my grandma’s siblings made sassafras tea from the roots of the trees that were in the backyard. This way of making sassafras tea has been in practice in North America for centuries, with Native American tribes being the first to develop it. Sassafras tea is a bit of an acquired taste; I definitely didn’t like it when I was younger. It tastes kind of bitter and syrupy at the same time in a way that isn’t very inviting to the unfamiliar palate, especially if you don’t add any sweetener.

It does, however, taste remarkably like root beer. This is because the sassafras root was the original flavoring agent of root beer until it was banned by the FDA for containing the chemical compound safrole, which has some carcinogenic properties. Nowadays, commercially sold root beer and other sassafras flavored food contains sassafras extracts without the safrole. That said, my opinion is that the chance of natural sassafras tea or root beer made from sassafras causing cancer is very low since it’s only been shown to be a weak carcinogen in rats.

Roots of trees and other plants have many functions, one of which is storage. For example, maples store most of their water and sugars in their roots over the winter. One of the things that sassafras stores in its roots is safrole, the compound that gives root beer and sassafras tea its distinct taste. Like with other chemical compounds or ‘secondary metabolites’ that plants produce, it is thought the tree makes and stores safrole as a chemical defense against harmful insects or pathogens.

Another function of some roots is propagation. Some plants, like aspen trees and sassafras, can form buds on their roots which can grow into whole trees that are clones of the first tree. Aspens, in particular, are famous for this, but sassafras too can clone itself and give rise to many other trees in this way.

These two functions of sassafras roots, though they serve very different purposes to the tree, look similar from my perspective. Sassafras uses its roots to propagate itself and, in doing so, creates a whole group of trees. At the risk of anthropomorphizing, it seems almost as if the tree is building a community or a family to live among. And thanks to it storing safrole in its roots, sassafras builds community for humans, too. Sassafras tea, for me, has never been an individualized activity. It’s always helped me make or strengthen my connections with other people.

The summer after my freshman year of college was really the first time I was living with my dad after my parents had gotten divorced the summer before. I’ve always been very close with my mom, so not living with her felt really lonely. One day, she and I were on the phone together, and she told me about her plans to go over to my great-grandma’s house, and dig up some sassafras root to make tea. A few days later, she came over to my dad’s house and dropped off a jar of dried sassafras root. The bitter, syrupy, root beer-y taste had never been so sweet and nostalgic as it was then.

Another time that sassafras helped me connect with people was during a summer I spent taking a field botany class, which included three weeks in the woods with a bunch of other college students whom I had never met. One person from that class knew how to forage for sassafras roots, and so one day he went and dug a bunch up. He and a group of us stole some coffee filters from the dining hall and made a very convoluted filtration device with some tongs and clothespins, and we all had tea together. Most of us had never had sassafras tea before, so we sweetened it with brown sugar. And of course, more went into forming friendships with my classmates than just drinking tea together, but this was a foundational experience of those friendships.

So next time you drink root beer or a sassafras-flavored tea, drink it with a friend. The memories will be so much sweeter because of it.

Sam Hickman studies ecology at the University of Pittsburgh, where she works in the Ashman Lab as a research assistant.

By: Kathryn Barto

When I was a young kid, my grandparents moved to the Black Mountains of North Carolina. Although on the edge of the American South, it was still the farthest south any of my family members had ever lived before. Going to visit them for the first time, I marveled at the new environment, so different from New York. Looking out the car window at the nearby trees, I spotted a mass of vines and leaves that covered the forest and stretched as far as the eye can see. As we got closer to my grandparent’s house, the vines grew thicker and thicker, seemingly swallowing the entire forest in a green blanket. I’d never seen anything like it in my life. Highways and road cuts were surrounded by the stuff and it was all you could see when traveling. Later I learned that all of this vegetation came from a single invasive species called kudzu.

For eight years of my childhood, I went to a summer camp nestled in the Blue Ridge Mountains, just 15 minutes from my grandparents house. Being from New York and then Ohio, my family would make the several hour journey to and from North Carolina every year. Every time we would pass kudzu on the drive, I would marvel at the amount of coverage and the sheer growth of the vines coating the roadside. It seemed like it would eat the entire South at the rate it was spreading.

The summer camp I went to was an all girls camp in the middle of the woods. For two weeks, I was cut off from both the internet and the real world. Looking back, the difference in the forests near the highway and the one surrounding the camp cabins was astounding. Where one was a blanketed mess of vines, the other only had small islands of kudzu surrounded by a diverse ecosystem. Even as a kid, I recognized that kudzu was a problem and its spread could be environmentally destructive.

Kudzu’s monstrous growth is mostly due to its ability to reproduce vegetatively. Kudzu plants have specialized stems called stolons, which can creep along the ground and spawn new plants that are identical clones to the original. If you’ve ever grown strawberries, this is similar to how strawberry plants send ‘runners’ or side shoots that eventually grow into new strawberry plants. Kudzu plants also have another type of modified stem called rhizomes. The ginger you buy at the store is also a rhizome. In the wild, rhizomes stay in the ground over winter and can regrow aboveground in the summer. These allow the kudzu plants to survive year after year, even if cut down or physically removed. Finally, Kudzu vines can sprout roots if touching the ground, adding another point of contact to collect water and nutrients. With all these extra ways to spread, it’s no wonder kudzu has been able to grow rampantly in the South, outside of its natural range of eastern and southeastern Asia.

In the weeks before and after camp, I would stay with my grandparents in their large house on top of Black Mountain. Some of my favorite memories are linked with that house and being able to spend time with family. These moments together were also where I eventually earned the nickname “Kudzu”. When I say that I grew quickly as a kid, I don’t say it lightly. I was consistently one of the tallest people in my grade until high school and was always in the 90th percentile or above when compared to other kids my age. Because I went to camp from 3rd to 10th grade, it seemed that every time I visited my grandparents I had grown significantly. Every time, my grandmother would say I grew like kudzu; this transitioned into her calling me “Kudzu Kathryn” or just “Kudzu.”

My grandmother still calls me Kudzu despite my height topping out at 5 ‘8’’; every time she does, I’m brought back to that moment in the car, seeing the towering mat of kudzu zooming by the window and marveling at its ravenous spread.

Kathryn Barto is a 20-year-old, third-year student at the University of Pittsburgh who is double majoring in Geology and Ecology & Evolution. 

By: Manoj Kuppusamy

Have you ever had a canker sore?

Most people have, those annoying little white ulcers on the inside of your lip that seem to sting no matter what you do. A couple of years ago when I was suffering from a particularly bothersome sore, I mentioned it to my mother in passing, and I was intrigued when she said she had a solution. She sauntered over to the freezer, and pulled out a green box filled with curious looking brown balls. She only knew the name of the ball in our native Tamil language, (மாசிக்காய் masikai) but after brief internet exploration, I found that the English translation is “oak gall” or “oak-apple”. 

The galls were no bigger than a marble, and they had the appearance of a round nut, similar to an acorn, with small spiky nibs around the circumference. She split a gall in half with a pestle, and told me to go to sleep with the oak gall under my lip, on top of the sore. I had some difficulty falling asleep with a foreign object in my mouth, but when I inspected the sore in the morning, I was in for a surprise. The gall was stuck to the canker sore, it seemed to have shrunk and was covered in a stringy white substance that created webs around my lip. I removed the gall, and found that the canker sore was enveloped in the same string. I was able to peel the white substance from the canker sore easily, and found that where there used to be a red inflamed ulcer, now there was nothing! My lip was back to normal, and the only reminder was a small scar on my inner lip that left within the next couple of days. The holistic remedy that my mother gave me worked, and really well at that!

After my experience with the healing properties of the oakgall I was intrigued with how it worked, and why this medicine wasn’t more popular. This piqued my curiosity, as I’m sure it piqued yours: what even is an oakgall?

Oak galls, even though they look like a nut, are not nuts at all. In fact, they aren’t even something that oak trees make themselves, instead they are the result of a fascinating interaction between two different species!

First, lets examine how an oak gall is created. Female gall wasps, or gallflies, small insects similar in size to a fruit fly, will lay eggs on an oak leaf. Using its ovipositor (the egg-laying organ) the gall wasp injects chemicals that mimic the function of plant hormones, such as the growth hormone auxin, into the leaf tissue. The chemicals that the gall wasp injects cause the tree to react in a peculiar way: the leaf will curl around the eggs in the shape of a sphere. The abnormal tissue that now surrounds the egg-laying site is called a gall, and it provides both shelter and a food source for the larvae inside. Once the wasp larvae have completed their development, they pupate and eventually emerge as adult wasps boring holes in the gall in order to leave. Over time, the now empty gall will harden and become woody, providing a long-lasting record of the interaction between the oak tree and the gall wasp.

Now, how do these oak galls work to provide such immediate relief to canker sores? The answer lies within the peculiar chemical make up of these fascinating nests. Oak galls contain high concentrations of tannins, a naturally occurring chemical compound that is responsible for the dryness of wine, the strange dry feeling in your mouth after biting an unripe plum, and for curing leather. Tannins are astringent, which means they cause the shrinkage of body tissue. The high level of tannins in oakgalls mean that over time they will cause an ulcer to shrink and tighten to the point where the once inflamed skin is now less exposed.

So now the mysterious oak gall is less of a mystery to me. However, I will continue be amazed by its story, which starts with an oak tree and a tiny gall wasp and ends with a unique home remedy that I will be keeping in my freezer for the foreseeable future.

If you’re interested in reading more about galls and their real-world applications, check out this article.

Manoj Kuppusamy is a senior at the University of Pittsburgh majoring in Biology, where he is a research assistant at the Geriatric Psychiatry Neuroimaging Lab.

by: Nathália Susin Streher

This blog was originally published in the Carnegie Museum of Natural History website

Do you ever wonder what made you pursue your dreams in life? When I ask myself this question, it inevitably takes me back to my childhood and the indelible memories that growing up in the most biodiverse country in the world left on me. From the diversity of fruit trees and the tiny animals that crawled them in my backyard to the varied ecosystems in the surrounding areas, living in Brazil has shaped my perception of nature and sparked a singular curiosity about the variety of forms and interactions I could observe. As the little scientist in me grew up, fueled by the fascination with the beautiful mysteries of flowers, it naturally guided me toward the path of studying plants and their interactions.

As I stepped into the world of science, my first paid opportunity as an undergrad in biology was in a small herbarium. There I learned about preserving plant specimens collected from nature and their importance for identification and classification of plant species. What I did not realize back then was that herbaria store more than just names and relations among species; they also provide a means to investigate ecological interactions like the ones that captivated me as a child. I kept that flame of curiosity from my childhood alive and came to the US as a postdoc researcher. My research group at the University of Pittsburgh and I have been incorporating some unconventional uses of herbarium material into our research. In a recent scientific publication, we used herbarium specimens (many sourced from the CMNH’s herbarium) to explore a crucial ecological mutualism between animals that visit flowers for food and plants that require go-betweens to transport their pollen—a process called pollination.

In pollination biology, it is common to investigate floral characteristics because they play a crucial role in mediating plant interactions with their pollinators. For example, plants with long floral tubes are typically pollinated by morphologically matching long-tongued pollinators. While certain floral traits, such as visible color and scent, may be altered or completely lost during the drying process of plant specimens, many of the other characteristics remain accessible even after years of preservation. Thus, as long as the herbarium sheet contains at least one flower, valuable biological information can be extracted to understand plant-pollinator interactions. 

In this study, we used herbarium specimens to reveal the network of past plant-pollinator relationships. Specifically, we sampled a small piece of the flower, the stigma, which is the structure that receives pollen grains delivered by pollinators. As pollinators may visit several plant species flowering together, inspecting stigmas can unveil a plant’s pollination story. By assessing the diversity of pollen grains morphologically distinct from the target species, we gain insights into whether the target species interacted with many or only a few other plant species through pollinator sharing.

Leveraging herbarium specimens for ecological questions offers a unique advantage, as they provide historical, spatial, and long-term perspectives to scientific studies—dimensions that may otherwise be challenging to attain. In studies of plant-pollinator interactions, researchers often rely on direct pollinator observation data, which, while ideal, has limitations such as being time-consuming, costly, and dependent on various conditions. Pollen deposited on stigmas of herbarium specimens arises as a valuable alternative when direct pollinator observation is unfeasible. Herbaria offer scientists a convenient way to compare numerous plant species from around the world. Actively incorporating these specimens into research not only keeps the collections dynamic but also magnifies their overall significance. Much like the plant-pollinator interaction—it’s a win-win scenario. I hope our work inspires others to perceive herbarium collections as guardians of biodiversity and encourages scientists to unlock the hidden potential of their precious specimens.

Beyond the scientific excitement of unraveling the pollination story within herbarium specimens, I once again seemed to have missed yet another potential interaction they could reveal. While going through the cabinets housing the specimens at CMNH, I unexpectedly encountered plants collected from the same region where I was born and raised in Brazil. I never thought that an old, dried plant could make me feel closer to my homeland. Living abroad to pursue the scientific dream is no easy feat—different language, different culture. But that moment was a reminder of my childhood connection with nature that brought me here. Now, I see herbaria not only as guardians of biodiversity but also as promoters of a sense of belonging in us.

Nathália Susin Streher is a postdoctoral research associate in the Ashman Lab of University of Pittsburgh.

By: Veronica Iriart

This month, I made the long trek to Buenos Aires, Argentina to attend an important family event. Amidst all the visits with my aunts, uncles, and cousins, I was reminded of a key component to Argentinian culture that I never before thought about through a botanical lens: yerba maté.

Yerba maté is a strong-tasting herbal tea that’s made by steeping dried leaves of a subtropical, evergreen plant (Ilex paraguariensis) with hot water. The first thing you notice after drinking maté is its strong, bitter taste, and the second is its ability to wake you up! At 78 mg of caffeine per cup, maté has almost as much caffeine as coffee (85 mg per cup).

Typically, maté is prepared in a gourd and drunk through a bombilla, a metal straw that has a filter at the end to allow the tea to pass through but not leaf chunks. The Guaraní people who lived in what is now Paraguay were the first to make maté prior to European invasion of South America, and they did so by using natural gourds made from the calabaza plant (Lagenaria vulgaris). Interestingly, ‘calabash’ gourds are still the most common maté gourds, and the word ‘yerba maté’, which is a mix of Spanish and Quechua, literally means “herbs from the calabash.” Today, maté is still heavily consumed in Paraguay as well as in Argentina (the world’s largest maté producer), Uruguay, and Brazil.

What this long history of maté meant for me was a strong association between maté and my Argentinian relatives. In fact, whenever I think about my maternal aunts, two religious maté drinkers, I imagine them with gourds readily in their hands. Because unlike in the US where coffee or caffeinated tea is generally reserved for the morning hours, many Argentines like my aunts drink maté continuously throughout the day. In particular, drinking maté is often a social event, where friends pass it around the dinner table while they catch up on their everyday lives. Unfortunately for me growing up, my tastebuds did not immediately acquire a taste for maté, so I would often opt to drink a soda with my family over sharing maté on these occasions, but now that I’m older I can appreciate more the healthful benefits of this rich drink. For instance, besides caffeine, maté is also packed with many antioxidants and nutrients that have anti-inflammatory and cholesterol-lowering properties.

            If you’re interested in trying maté in the States, the company Guayakí has taken a modern approach to producing it with wide success: they make yerba maté sparkling cans, energy drinks, tea bags, as well as packages of loose leaves to make it the traditional way. Like with coffee, there are many ways to sweeten the bitter taste of maté by adding sugar and cream, i.e. making a ‘maté latte. Give it a try and see if you can enjoy the health and social benefits of maté like an Argentine!

Veronica Iriart is a recent PhD graduate from the Department of Biological Sciences at the University of Pittsburgh where she studied plant ecology and evolution in the Ashman Lab