10 Plants That Are Banned in Certain States

Japanese knotweed arrived in the U.S. as a fast-growing ornamental privacy screen and erosion-control plant, but its rapid growth soon proved a liability. It spreads through an aggressive root system that can push through pavement, foundations, and drainage pipes. The plant forms dense stands along riverbanks and roadsides, which crowd out native plants.

Even more problematic, cut or disturbed fragments regrow easily, making it notoriously hard to remove once established.

It’s not allowed for cultivation or sale in Connecticut, New York, Massachusetts, Michigan, and Vermont.

American gardeners imported this northeastern Asian native in the 1860s as a hardy new shrub. The appeal was obvious: brilliant red foliage in autumn gave the shrub its common name, burning bush.

However, the shrub grows aggressively. Birds love its equally brilliant red berries and disperse the seeds into nearby woodlands. There, the shrub forms dense thickets that block sunlight and crowd out native plants.

Burning bush is now off-limits in Delaware, Massachusetts, New Hampshire, and Pennsylvania.

European settlers brought purple loosestrife to the US in the early 1800s as a garden ornamental. The wetland perennial produces striking purple-magenta flower spikes that pollinators love.

Although the tall spikes may turn heads in a garden, purple loosestrife behaves very differently in the wild. There, it forms dense monocultures in wetlands, crowding out the native plants that fish and waterfowl depend on.

It’s illegal to sell or grow it in Minnesota, Ohio, and Washington.

Victorian gardeners in Britain were drawn to giant hogweed's dramatic size in the 1800s. The plant crossed the Atlantic in the early 1900s as an arboretum showpiece.

Although its massive stature is impressive, with its towering white flower heads that can span two and a half feet, its sap causes severe burns and blistering on skin exposed to sunlight. It also crowds out native plants along stream banks and roadsides.

Giant hogweed is a federal noxious weed, banned from sale and cultivation in Alaska, Minnesota, New York, Florida, Pennsylvania, and Illinois.

Growers introduced Oriental bittersweet to the US around 1860 as an ornamental vine and erosion-control plant. The plant produces bright red-and-yellow berries, making it a popular choice for fall wreaths and decorations and a popular food source for birds, especially late fall and early winter.

However, if left unchecked, the vine climbs and strangles trees, its weight and reach eventually smothering the canopy. It also readily crosses with the native American bittersweet, threatening to erase the wild species altogether.

It can not be sold or cultivated in Connecticut, Ohio, and Delaware.

Water hyacinth made its US debut at the 1884 Cotton States Exposition in New Orleans. It was at the gathering where organizers handed out the pretty purple-flowered plant to attendees for their backyard ponds.

It escaped into the wild almost immediately, forming dense floating mats that block sunlight, drain oxygen from the water, and choke out native fish and plants. It’s one of the fastest-growing plants in the world, capable of doubling its coverage in less than a week.

It’s illegal to sell or cultivate in Michigan, Texas, Wisconsin, and South Carolina.

Common buckthorn was introduced to North America in the early 1800s as a hardy hedge and windbreak plant.

It leafs out earlier in spring and holds its leaves later into fall than most native species, letting it form dense thickets that block sunlight from reaching the forest floor. Birds then spread its seeds widely. The berries also act as a laxative, speeding the seeds' passage through birds and small mammals while sickening the animals that eat them.

It’s banned for sale and cultivation in Connecticut, Minnesota, and Illinois.

Garlic mustard arrived in North America in the 1800s as a culinary and medicinal herb. It escaped into the wild and now dominates forest understories, releasing chemicals into the soil that block native wildflowers like trillium and bloodroot from germinating, and it produces thousands of seeds per plant that scatter well beyond the original stand.

It’s banned for cultivation and sale in Washington, Minnesota, Illinois, New York, and Ohio.