About 5,000 nonnative plants have been introduced into the United States by humans either purposely or by accident. Though most of these plants are harmless, many are invasive species with great potential to continue spreading widely into new natural habitats. They majorly owe their success as pests to the fact that they’re easily spread through various pathways and vectors and they can thrive in disturbed areas. Once these unwanted invaders become established in an area, they can quickly spread across the landscape and remain the dominant plant. But these invaders are not just sitting pretty in their new habitat, they have the potential to cause significant economic and environmental damage.
8 Plants Invading the United States
Japanese Honeysuckle (Lonicera japonica)
Japanese honeysuckle, one of the invasive varieties of the honeysuckle plant in the United States, is found throughout the East Coast. It adapts to a wide range of conditions, hence its wide distribution. Many birds also eat the fruit of this plant, thereby contributing to the spread of its seeds. This is a plant originally native to Eastern Asia but was brought into Long Island, New York in 1806 for ornamental use and erosion control. It is an aggressive plant that smothers and shades other rival vegetation. The U.S Forest Service reports that Japanese honeysuckle spreads roughly 65,000 acres each year!
Cheatgrass (Bromus tectorum)
Cheatgrass originated in Europe or Eurasia and was introduced to the United States in the 1800s as a contaminant in seed and straw. This species grows rapidly and in high numbers, making them highly competitive with native plants. It is an aggressive plant with the potential to significantly contribute to the destruction of the rangeland ecosystem in the western United States. Areas dominated by cheatgrass tend to have increased fire vulnerability and low grazing value. Like other invasive species, it is considered problematic and causes huge economic losses.
Purple Loosestrife (Lythrum salicaria)
This beautiful purple plant originally hails from Asia and was introduced to the United States in the early 1800s for ornamental and medicinal uses. Though this species is a vigorous and adaptable perennial, it has invaded many states of the U.S. to slowly become the dominant plant species, especially in wetlands. One plant can produce as many as 2 million seeds per year and underground stems grow at a rate of 1 foot per year. If allowed to spread unchecked, it can cause damage to wetlands and affect the animals that live there.
Japanese Barberry (Berberis thunbergii)
Originally from Japan, the Japanese barberry plant was introduced to the USA in 1875 for ornamental purposes. According to history, the seeds of the Japanese barberry were sent to the Arnold Arboretum museum to replace the European barberry which carried a serious fungus affecting cereal crops (black rust stem fungus). This heavy fruiting shrub can grow in deep shade and its seeds are easily spread by birds. Japanese barberry forms a dense thicket, crowding out native plants, and slowly creating devastating changes to forest lands in Northeast America.
Oriental Bittersweet (Celastrus orbiculatus)
Oriental bittersweet is a woody, perennial vine native to Asia. It was introduced into the United States as an ornamental plant in 1860. Marked with beautiful berries in winter, its fruiting stems are used for decoration. But its beauty does not take away the fact that it poses a significant threat to the success of native plant species. It grows rapidly and can shade out other vegetation –confining trees and shrubs, and cutting off the flow of water and nutrients to them.
English Ivy(Hedera helix)
English Ivy originated from Europe but was introduced into the U.S by European colonists in the early 1700s. The importation of this plant was primarily because it was seen as an easy-to-grow evergreen groundcover. To this day, people in the United States continue to plant and sell the English Ivy, not minding that it spreads aggressively and slowly kills neighboring trees by restricting their access to light. It is considered one of the worst-spread invasive plants in the country because of its ability to withstand a wide range of conditions. It is spread by seeds that are eaten by birds, and by vegetative reproduction.
Norway Maple(Acer platanoides)
Native to Europe, the Norway maple has become a widely adaptable tree in the United States. In 1756, John Bartram, a plant explorer was the first to introduce the plant into the U.S from England. Norway maple was planted in rural communities and towns as a shade tree. However, it has the potential to displace native trees and dominate the landscape in the Northeast and Northwestern parts of the United States. It has been observed that it displaces native alternatives such as the sugar maple and its dense canopy shades out wildflowers.
Kudzu (Pueraria montana var. lobata)
Recognized as an invasive plant in the U.S since the 1950s, Kudzu – nicknamed “the plant that ate the south” – is a plant native to China, Japan, and the Pacific Islands. It was first introduced to the country in 1876 as an ornamental plant and for erosion control but it was eventually identified as an invasive species throughout the Southeastern United States because of its aggressive nature. It takes over landscape areas, with enough massive weight to smother other plants and trees or topple them. The U.S Forest Service estimates that the vine spreads by 2,500 acres per year while the Department of Agriculture estimates that kudzu spreads up to 150,000 acres annually! Despite the varying claims, one thing is for sure —this plant is invading the U.S wide and fast.
The photo featured at the top of this post is © iStock.com/Marina Denisenko
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