6 of the most invasive plant species in the world

Photo collage of various invasive plant species, photos and botanical illustrations, around a dilapidated house swallowed by a huge overgrowth of kudzu

(Image credit: Illustration by Julia Wytrazek / Getty Images)

last updated 12 December 2024

When any plant species is introduced to a region where it is not naturally occurring, it has the potential to become invasive and outcompete those native to the region. Because invasive species have no predators or competition in the new region, they often thrive at the expense of the native species around them. In the long term, this can cause ecological harm and even permanently alter an ecosystem.

Invasive species have been introduced both accidentally, like after attaching to a hull on a ship, or purposefully, through trade. Climate change is also "creating new pathways" for the introduction of invasive species, including "shipping routes that open up as sea ice retreats," and warmer temperatures allowing existing invasive species to "expand their range into habitats that are currently too cool," said the U.S. Geological Survey. However, "the vast majority of introduced species pose no danger at all to native ecosystems and in some cases can even provide new benefits," Heather Kharouba, an associate professor of ecology at the University of Ottawa, said at The Conversation. "In this changing climate, we need a more inclusive view of biological diversity that includes all species. What if some of our introduced plants are part of the solution and not the problem?"

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Japanese knotweed (Fallopia japonic) is a species native to eastern Asia that has been wreaking havoc in North America and in the U.K. It looks like a "clumpy, bushy bamboo plant," and "its white flowers, which appear in late summer, are beautiful," said The Wall Street Journal. It also requires very little care and grows quickly. "These qualities made it very popular with gardeners ignorant to the weed's inherent evils."

The beautiful plants can be deadly, as they can degrade wetland habitats. "Dense thickets can reduce sunlight penetration by more than 90%, and its thick mats of dead and decaying vegetation in fall/spring prevent other plant species from growing by shading them out," said the Invasive Species Centre. The knotweed is also allelopathic, "meaning it releases chemicals into the soil that inhibit the survival of surrounding plants," said Britannica. The plant can even destroy building foundations for new developments because it grows through concrete and asphalt.

The beloved golden bamboo (Phyllostachys aurea) plant is invasive in the U.S. and Europe. The plant is native to southeast China and has been cultivated in Japan for centuries; it was introduced to the U.S. in 1882 in Alabama and "became a popular choice for property owners wishing to develop a screening and/or noise barrier," said the University of Maryland Extension. "Others planted it with the intention of harvesting them for fishing poles."

While beautiful, the problems soon became evident. Golden bamboo can grow fast and aggressively, reaching heights of 30 to 40 feet tall. "It quickly overtook everything in its path, destroying native plants and the habitats they provide for wildlife, and offering nothing in return," said HowStuffWorks. Golden bamboo is not the only invasive bamboo species, either: the black and running varieties are also causing problems globally.

Hydrilla (Hydrilla verticillata), also called water thyme, is an invasive aquatic plant native to Africa and Southeast Asia. It has now made its way to Canada and the southern and eastern U.S. "It is extremely hardy and can grow in many conditions (including low light levels and poor nutrient areas)," said Cornell Cooperative Extension. It also reproduces quickly and can rapidly outcompete native plants.

"Hydrilla has been known to take over as the dominant plant in a lake in only three years after it's introduced," said The Columbus Dispatch. It can also cause an aquatic monoculture, which can limit food and habitat options for species and reduce biodiversity. Removing the plant is difficult: "Mechanical cutting risks spreading hydrilla by fragmentation," so "controls typically involve herbicides" and "drawing down reservoirs past the shallows where the plants thrive," said The Dispatch.

The deep south of the U.S. has been invaded by kudzu (Pueraria montana), a climbing vine with severe ecological effects. The plant is native to Japan and southeast China and was introduced in the U.S. in 1876. "An invasive plant as fast-growing as kudzu outcompetes everything from native grasses to fully mature trees by shading them from the sunlight they need to photosynthesize," said The Nature Conservancy. The plant is extremely resilient and able to thrive in a variety of conditions and soil types.

The water hyacinth (Eichhornia crassipes), native to South America, is considered to be invasive in over 50 countries, including those in Central and North America, Asia, Europe and Africa. While beautiful, the plant is "loathed for its ability to reproduce so quickly that it can blanket large portions of lakes and ponds with a thick mat of vegetation," said NASA's Earth Observatory. Because of this, lakes can quickly become overrun with water hyacinths.

The Asiatic or oriental bittersweet (Celastrus orbiculatus) is an invasive plant from Eastern Asia, found in Japan, China and Korea. The plant, known for its bright red berries, is invasive in the Northeast U.S., namely Connecticut and Maine. It is "often seen strangling trees on roadsides and ultimately destroying them," said the University of Connecticut. It grows as a vine and "smothers plants and uproots trees due to its weight," added the U.S. National Invasive Species Information Center.

Its berries are striking, making them ideal for decorations like holiday wreaths, but "turning them into decorations can invite the quick-spreading, hard-to-remove plant to quickly take over your yard," said Bangor Daily News. It can also pose a danger to wildlife. "Birds can eat the berries, spreading the seeds through their digestive system and establishing new plants. As wreaths are thrown out, or if they end up composted, they can spread new plants."

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Devika Rao has worked as a staff writer at The Week since 2022, covering science, the environment, climate and business. She previously worked as a policy associate for a nonprofit organization advocating for environmental action from a business perspective.