‘Passengers to Human Movement’

When importers shipped porcelain from China to the United States in the early 20th century, they would nestle it in stiltgrass to ensure its safe journey across the Pacific Ocean. 

At the time, no one anticipated the damage that this packing material—a dense, fast-growing annual grass common in Asia—would cause across North America. Stiltgrass seeds found their way into forests and other habitats where they took root and spread, threatening fauna and wildlife throughout the continent.

Stiltgrass is one of the many invasive species featured in Carnegie Museum of Natural History’s new exhibition Uprooted: Plants Out of Place, opening on March 22.

Rather than sound the alarm about plants like stiltgrass, however, the goal of the exhibition is to help visitors reflect on humans’ role in introducing invasive species, and how they can manage the problem, says Sarah Crawford, the museum’s director of exhibitions and design.

“One of the things we really want to drive home is that human actions and concepts of stewardship shape the past, present, and future of invasive plants,” Crawford says. “We are the ones that move these plants around.”

The exhibition caps two years of research by associate curator of botany Mason Heberling and postdoctoral fellow Rachel Reeb that was funded by a $225,000 grant from the Richard King Mellon Foundation. Uprooted will be on display in the Hall of Botany and the overlook on the third floor, where visitors will learn about the history of certain invasive plants in the United States, read stories from community partners working to manage them, and view a photography exhibition that recontextualizes how one species in particular—knotweed—has thrived in different habitats around the world.

“One of the things we really want to drive home is that human actions and concepts of stewardship shape the past, present, and future of invasive plants. We are the ones that move these plants around.”

–Sarah Crawford, director of exhibitions and design, Carnegie Museum of Natural History 

The exhibition challenges the binary ways we tend to think and talk about invasive species, Heberling says.

“You think, oh, it’s a pretty easy topic, right? Native and non-native, this plant belongs here, this plant doesn’t belong here. This plant is good, this plant is bad,” he says. “Even in a scientific sense, it’s much blurrier than that.”

Invasive species are any plants, animals, or other living organisms that cause economic or environmental harm to ecosystems where they are introduced. They are a massive problem around the world—costing an estimated $1.3 trillion to the global economy over the past 50 years, according to the U.S. Department of Agriculture. Just as concerning to many experts is how the issue is discussed with the general public.

Value-laden language, such as “alien” or “villain,” that anthropomorphizes invasive species places the blame on the plant and minimizes human responsibility, Reeb says. In actuality, invasive plants are “passengers to human movement,” she notes.

A photography display in the museum’s third-floor overlook uses Japanese knotweed to explore how perceptions of a plant change with context. Japanese photographer Koichi Watanabe has documented knotweed’s presence around the world. It’s highly valued as a culinary and medicinal herb in Japan, yet it’s considered one of the most harmful plants in Pennsylvania.

An interactive station encourages visitors to group plants based on their personal feelings, positive or negative, before flipping a panel to reveal whether the plants are native or introduced.

Meanwhile, the museum’s Hall of Botany focuses on three species: stiltgrass, multiflora rose, and garlic mustard. Three display cases examine each plant’s impacts through herbarium and animal specimens, photos, and art.

Stiltgrass is the only one of the three that was accidentally introduced in the United States. Garlic mustard was intentionally brought here for culinary and medicinal uses, but it releases chemicals that disrupt microbes in soil. A smell station and historic books will showcase its potential in cooking.

Multiflora rose was brought here as a decorative plant and a form of erosion control, and was once approved by the United States Department of Agriculture. But it can have a detrimental impact on the environment, which will be shown through bird, tick, and mouse specimens.

These exhibits demonstrate how perceptions of plants shift over time. Not every invasive plant is currently banned—some are even sold at garden centers. An interactive plant stand highlights common invasive species sold in the plant trade, reminding   visitors to be mindful as they plant their own gardens.

The museum is also updating a few dioramas to include information about the three invasive plants featured so as to challenge “idealized views of nature,” Crawford explains.

The exhibition also spotlights how local organizations such as Pittsburgh Parks Conservancy, Allegheny GoatScape, and Garfield Community Farm are addressing invasive species.

Heberling and Reeb want visitors to feel empowered, not helpless, to manage invasive plants. It’s all about the small actions that people can take—such as planting native species in their own yards—that will have big impacts.

While human actions are the source of the problem, they’re also the solution, Reeb notes.

“These species are here today and are causing the specific harmful effects that they cause because of somebody else’s actions in the past,” she says. “And there are a lot of things that people can do to support overall environmental health, support biodiversity, and support their communities.”