The world’s biggest online auction platforms, like eBay, boast all kinds of miscellany, including clothes, electronics, cars, and many an eccentric novelty item. Some websites also allow the trade of flowers and plants, offering users the chance to buy and sell botany from around the world.

It sounds innocuous—a niche trade that lets plant enthusiasts enjoy a wide spectrum of plant species without having to personally travel to other countries to find them. But a team of Swiss researchers warns that the plant trade may be much more harmful than it appears.* Turns out, online plant sales raise the risk of spreading invasive species to new regions.

Researchers led by Christoph Kueffer from the Institute of Integrative Biology tracked for 50 days the world’s online flora trade through eBay and nine other auction sites. Their findings, published recently in the journal Conservation Biology, show that 2,625 plant species were on sale over that period from 65 countries, and 510 of them were identified as an invasive species in at least one region of the world.

In addition, 35 of the plants are on the International Union for the Conservation of Nature’s list of 100 worst invasive species. Passionfruit was the most commonly sold invasive plant, offered by sellers 90 times a day.

An invasive plant species is one that, when relocated to a new environment, grows aggressively, nudging out other plants and choking out natural biological diversity. They don’t pose a threat to their indigenous environments because they’re already adapted to those plants. When introduced to foreign areas of the world—through, say, a person’s desire to keep an exotic personal garden in their backyard—invasive plants mess with a region’s soil, insects, pathogens, and risks of fire.

They also pose a grave threat to endangered animal species. And if they get near lakes or ponds, they can contaminate public water.

“We didn’t expect the global trade in plants that are known to be invasive to be so extensive,” said Franziska Humair, the lead author of the study. Kueffer also noted that there are seemingly no controls in place to make sure potentially harmful plants don’t leave their original countries or continents—even in countries like Australia, which don’t allow invasive plants to be brought in.

The researchers—who warn that the real number of online invasive plant sales is probably greater than what they found, since they tracked only scientific names and not common names—are urging national authorities to start looking more closely at the global trade of plants.

Just last week, a fast-growing aquatic plant dubbed the “Godzilla” of invasive species was discovered lurking in a pond in New York.


* This article originally misidentified the researchers as Swedish. We regret the error.