PERSPECTIVES 01: Adventive America

In advance of the 2026 semiquincentennial of the United States, marking the 250 years since the signing of the Declaration of Independence in Philadelphia in 1776, graduate student researchers have been assisting Catherine Seavitt, Meyerson Professor and Chair of the Department of Landscape Architecture, with a McHarg Center project entitled “Adventive America.” The project explores the narratives of the botanical exchanges of the early republic, acknowledges the agency of plants at both the 1876 Centennial Exposition and along the Delaware River’s wasteland shores, and invokes the critical spirit of the grassroots People’s Bicentennial Commission of 1976. The Centennial Exposition, held at Fairmount Park during the aftermath of the Civil War, reveals fascinating threads of international relations and exchange, the global movement of plant materials, and the role of plants in the economic and industrial history of the United States. With the upcoming 250th anniversary in Philadelphia, this project uses a nontraditional lens to think critically about the making of a nation.

Research assistant Elizabeth VanDerwerken (MLA, MCP ’27) spoke with Catherine Seavitt about the ongoing Adventive America project as well as the broader research interests that inform her work.

Elizabeth VanDerwerken  Laura VanKoughnett and I have been working with you since last summer on the Adventive America project, and we are familiar with recent projects you have done through the McHarg Center looking at Indigenous plant knowledge and digital modeling of ballast species. Can you describe how your past research interests have led to Adventive America?

Catherine Seavitt  Much of my design research work has played out in the New York environs around coastal Manhattan, particularly the shorelines around New York’s Upper Bay and Jamaica Bay, which spans the boroughs of Brooklyn and Queens. My work at Jamaica Bay explores questions about risk: what is at risk of flooding, and how can we recover and support the restoration of wetlands to reduce that risk? This work also questions things that are at the margins, which are always the most interesting to me. Wetland, as its name implies, is literally a margin between water and land. It’s a pretty curious thing, because it’s neither totally wet nor totally land, but always in this transforming condition of being somewhere in a gradient between wet and dry. Much of the work that I was doing with the US Army Corps’ New York District post-Hurricane Sandy involved exploring novel ways to do marsh restoration, which at Jamaica Bay was about various strategies of moving sand from one place to another—there was this idea that building land is always a displacement activity. Even a restored wetland is made land.

My current research on the sanitary engineer and unlikely environmentalist George E. Waring, Jr. extends back to his personal feuds over the design of Central Park with the land surveyor and engineer Egbert Viele. Viele created the beautiful “water map” of Manhattan—he uses three colors of land to code that drawing. On the legend, he identifies the colors as marsh, meadow, and what he calls “made land.” 

Made land is coded in brown, and it’s basically all landfill, or what is sometimes called “anthrosol,” meaning soil formed by human activity. During the extreme flooding of Hurricane Sandy in New York City back in October 2012, which informed much of my design research as an academic, people went back to the Viele map and noticed that the places that flooded during Sandy were pretty much co-extensive with the “made land” of his water map. There was a direct correlation between made land and vulnerability—those areas had just been filled to an elevation considered to be terra firma, and not water anymore, a conversion of wet land to dry land. I’ve always found that liminal territory of made land interesting.

EV  This is something that stood out to me from the very beginning of our Theory course that you taught in Fall 2023—that the margins are worthy of our attention and investigation. In our research meetings, you have also referred to the ground as an archive—how does that function on made land, which is formed by moving material from one place to another? If the physical ground is literally being moving around, how can it hold an archive, and do the conditions of that archive change?

CS  Several years ago I came across the work of Maria Thereza Alves, a Brazilian artist who explores that territory of “made land.” She had been looking at the transportation of ballast materials around the world through maritime commerce. I visited an exhibition of her work in New York where she was propagating plants from seeds that had unwittingly traveled along with that ballast. I had never heard of a ballast plant, so I looked into that some more. As wind-driven sailing vessels would traverse the Atlantic Ocean between Europe, Africa, and the Americas, they needed weight or ballast to keep the ship from capsizing in the wind. Rock, sand, and gravel material would be placed into the hold of the ship as it would leave from Bristol or Liverpool or another port city.

This material, which was seen as dispensable, was dumped on arrival, so the ship could then be filled with cotton or lumber or other commodities and sent back to Europe. Even though that rubbly ballast material was considered waste, it was in fact being used productively to expand the old waterfront and create new land. Seeds also came along with the soil and gravel material from these other locations, and the plants that germinated on the ballast grounds were of great interest to local botanists back in the nineteenth century.

Alves’ work opened up new territories for me about what made land really was, and I thought a lot about how this was a kind of rediscovered, out-of-place archive. I also discovered a lineage of plant collectors who were interested in the plants emerging from this kind of made land—the same lands that Viele had mapped, and that the Army Corps was actively remaking. So the idea of an archive, and capturing things of the past, gets completely reconsidered when it is spatialized as ground, because land itself is constantly being extracted, moved, and remade.

EV  Could you describe one of your favorite ballast plant species? Have any of these ballast species shown up in unexpected places in your research?

CS  Of course! Diplotaxis tenuifolia, which is also known as wall-rocket, was one of the ballast plant species that kept coming up when I was digging into the old journals of the Torrey Botanical Club and the New York ballast plant collectors’ herbaria. This is an ongoing interest of mine: plants that are out of place and that appear spontaneously in places where they're unexpected. I especially like Diplotaxis, mostly because I have a beautiful image of it—it’s a pressed herbarium sheet specimen from one of the ballast sites at Hunter’s Point in Queens, collected by Addison Brown in 1879. He wrote about the plant in the Torrey Botanical Club’s Bulletin, describing it as “an almost invariable index of ballast ground.” So seeing this plant is a signal that you're on ballast land. I love that idea of the plant as an indicator—if you saw Diplotaxis, you knew you were on a different kind of disturbed ground.

I was able to see this actual specimen of Diplotaxis tenuifolia and many other ballast species at the Steere Herbarium at the New York Botanical Garden. I remember walking through the herbarium storage shelving with Vanessa Sellers, who was working with the Botanical Garden’s library. As she pulled out the herbaria sheets, she said, “Isn’t this amazing? These are still living things. This is DNA.” To look at plants from over a century and a half ago and think of them as alive made that explanation very real and vibrant. I was completely fascinated by that realness and vibrancy, and the care with which someone had collected, printed, pressed, thought about, and labeled their impressions of a plant and a place. It felt like a living archive, even though it was just flat, desiccated plants. This idea of marginal space that was so anonymized on Viele’s maps started to be enlivened by these living beings sprouting from the grounds that had been transported from around the world to the North American coast.

EV  I love this idea of herbaria sheets containing living material—it really connects this idea of the ground as an archive, containing seeds and traces of geologic history and other organic material, with that of the literal archive, in this case, containing plants and the knowledge and DNA that they hold. What connections did you discover between your work in New York, your interest in ballast plants, and Philadelphia?

CS  I learned that there was an earlier episode of ballast plant collecting going on even before the New York botanizers—Addison Brown and others in the New York area were basically modeling their botanizing expeditions on work that had been done in Philadelphia over ten years earlier. Aubrey Smith, a member of the Academy of Natural Sciences in Philadelphia, first started exploring the ballast grounds along the Delaware River in the 1860s. He noted that it was the geographic location and local climate of Philadelphia that made it possible for these species—which tended to be a bit more southerly or tropical—to do well on these “waste grounds.” Philadelphia’s placement on the Delaware and the nearby bluffs created a greenhouse effect of warmth and protection from the wind for these plants.

Philadelphia was also the birthplace of science in the so-called “new world,” given the curiosities of Thomas Jefferson, Charles Willson Peale, Benjamin Smith Barton, the Bartrams, and others. These folks were really interested in the natural sciences and wanted to understand plant life more fully—particularly William Bartram who had many exchanges with Indigenous peoples and their knowledge of plants during the eighteenth century. The ballast plant collectors of the nineteenth century were networked—they were looking at this new, weird, intercontinental flora and pressing it, collecting it, identifying it, and sharing their observations with other people. The use of plants to create an exchange of knowledge is fascinating—the herbaria sheets were physical things that could be shared, classified, and re-classified.

EV  It’s great that there are threads connecting the New York ballast-botanizing scene with their Philadelphia counterparts. Since coming to Penn and extending the area of your research to Philadelphia, have you encountered any interesting stories about the Philadelphia ballast plant collectors?

CS  Here’s an interesting character with a great storyline from that group: Isaac Burk. He was not an elite lawyer or professor like many of the other botanizers; he had a newspaper route, and as he was doing his rounds, he discovered these ballast grounds and “waste lands” and became an obsessive plant collector. His lists of plants were published in the journal of the Academy of Natural Sciences, and he became well-known to the plant collecting world of that time. Burk also has some quirky connections to the Centennial Exposition that was held in Fairmount Park that we’ve been studying as part of Adventive America.

I had thought his interest was limited to ballast plants, but it turns out that he was also collecting and writing about the native flora around Fairmont Park in the 1860s and 1870s, and he also visited the International Exposition in 1876. He noted that alfalfa (Medicago sativa) was showing up both on the ballast grounds along the Delaware as well as in the exhibitions at Horticultural Hall. The plants on display at Horticultural Hall are kind of stowaways, too, in a sense: they're being brought in by humans for display purposes and highlighted as agricultural or industrializing agents in the reconstruction of the nation after the Civil War. Burk was an interesting crossover figure, interested in both ballast flora from afar as well as unusual local flora. For example, he collected a pawpaw specimen (Asimina triloba) from Fairmont Park—on the herbarium sheet, he writes “native,” almost like an exclamation point. 

EV  Burk’s exploration of plants on the ballast grounds, at Horticultural Hall, and at Fairmount Park more broadly connects many of the threads of your research. I know you have been doing some work on the pawpaw as well—can you tell us more about that?

CS  I actually had never heard about the pawpaw until I arrived in Philadelphia! New York is just a bit out of that tree’s native range. It’s such an interesting species, an understory tree that produces the largest edible fruit of North America. Noncommodifiable, somewhat forgotten. I spent some time with your classmate Nitya Patel working on Indigenous foodways and specifically the pawpaw, as part of my research for a forthcoming chapter in a book on the University of Pennsylvania’s campus landscape.

Isaac Burk is an unusual kind of researcher—he’s really interested in plants for plants’ sake. He’s observing the everyday and the extraordinary at the same time, whether the native plants like pawpaw and Virginia creeper (Parthenocissus quinquefolia) that he collected around Fairmont Park, the exotic tropical species on display at the Centennial, or the overlooked but quirky marginal plants he found along the Delaware riverbank wastelands. This was all worthy of study to him.

EV  Can you tell us more about the name Adventive America—both what it means and what it reflects about the ethos of the project?

CS  I like to have a secret production code-name for all the things I’m working on! “Adventive America” had a nice ring to me, and a multi-layered message. “Adventive” is a botanical term often used to describe the characteristics of ballast flora. I love that term, because it doesn’t imply that they’re invasive, that they’re exotic or alien; it has this sense of positivity and ingenuity of spirit. “Adventiveness” is botanically defined as a species that is not of the place, not “native,” but has arrived, intentionally or not, by some other force, usually by humans—there's this notion of movement or change of place, and about something persisting on its own.

I also like that “adventive” sounds almost like “inventive,” and I appreciate that kind of double entendre. At Penn, people are always talking about Benjamin Franklin and his role as an inventor and scientist. The spirit of invention has always been of great interest to me, and I love that adventive plants are also inventors, in the sense that they're creating new ground, new territory for themselves. They are thriving in places where they are least expected, and they also show tenacity, which I think is really necessary in a rapidly changing climate—it’s the tenacious plants that are going to make it.

“Plants as Inventors” is also the title of a great little book from 1920 by an interesting German writer, Raoul Heinrich Francé. He looked at plants and plant morphology as a way of linking nature and technology, creating connections between modern industry and plant life. And then, we can tag on “America,” because this is the spatialized territory in which this exploration is being done—it’s the construction, literally, of America and its margins and edges that is producing the spatial condition for this adventiveness. I think this ties in nicely to the overarching theme of the 250th, of looking at the history of America, fraught and imperfect as it is and continues to be. Can there be a way of thinking through these notions of made land, of thinking about things that are “native,” as well as things that have maybe never been spotted here before, but seem to be making their way? There’s a lot of nuance in that title that I like, and the idea of using a nontraditional perspective and lens to think critically about the making of a nation.

EV  With that framing, can you share a bit more about the project of Adventive America, and what we’ve been looking at together?

CS  You and Laura have really been researching this conversation between the quirky ballast plant collectors along the Delaware shores, and the more formalized world stage of the 1876 Centennial Exposition at Fairmont Park in Philadelphia. With the upcoming 250th anniversary of the signing of the Declaration of Independence, Philadelphia is getting a lot of attention. I’ve been thinking about this proxy lens of a botanical history of the nation, from the early days of colonialism and contact in North America through to today—what does it mean to think about plant knowledge and knowledge exchange? And what can we learn from plants?

In the era of 1776, this question takes us back to John Bartram, William Bartram, Benjamin Smith Barton, and others who were in conversation with the Lenape and other Indigenous peoples about plants, particularly their value in terms of medicinal, edible, and other “useful” qualities.

A century later in 1876, the United States was a torn nation, trying to reframe its identity in the aftermath of the Civil War while celebrating its centennial of independence. This is a fascinating thing to examine: what goes on an international stage when you’re in that place of repair? What do you showcase? There are two exhibition spaces at the Centennial Exposition that I find pretty fascinating: Horticultural Hall and Agricultural Hall. Plants were on display as part of this idea of progress, a new revolutionary moment in a nation that was then one hundred years old. What were the plants that were caught up in this celebration of industry and progress? What has happened since then, and how are these plants seen today?

How do plants serve as proxies or knowledge-bearers of what was going on with the nation, maybe coded in different ways, and how does that extend to our relationship with other people? With Indigenous peoples, with women, with newly liberated Black people? I feel like many of the implications of the displays at the Centennial carry a subtext of demonstrating how plants were really going to advance the industrial mission of the nation at that time, but they also reveal how we were constructing complex social relationships. And I see this as a pretty interesting critical lens with which to examine the upcoming 250th anniversary, particularly given the current political moment and a general sense of precarity that doesn’t feel particularly celebratory.

EV  Thank you for sharing how these different interests and projects have led to this current research effort. What advice would you give to your students about research and how to improve their research skills?

CS  It’s probably the same advice I would give to myself—try to be organized, but don’t worry too much about a bit of messiness. Research is really a process of collecting, so how is the collection organized? Do you throw it all in one drawer, or do you have different drawers for different things? Don’t be too obsessive about the organizational strategy, though, because sometimes when you put something in the wrong drawer, you open up new possibilities and unexpected connections. I’ve always loved archives—you never know what you’re going to find in there.

I'm always moving a bunch of projects along at the same time. As much as I hold them in different folders or subfolders in my mind, there's a lot of overlap. Sometimes those points of tangency are literal overlaps, and sometimes they're just tangential moments that touch. With the research process, how do you follow a line of thought, and where does it take you? There’s something interesting about looking beyond what you thought you were looking for, being open to discovery, and thinking through chance encounters. Maybe it’s more than luck to have stumbled across something you didn’t expect. There are always more questions to be asked, and sometimes you answer them with more questions. Keep an openness to any kind of research, which has the word “search” embedded in there, plus “re-”: do it over and over. Continual searching is an approach to knowledge as a wonderful and unattainable thing. Be open to what might emerge that might give you something new and beautiful that you hadn’t expected at all.

This interview was conducted for Perspectives 01, Fall 2025, and has been edited and condensed for clarity.