For centuries, invasive species of plants have been finding their way out of their native habitat to grow freely in other lands and nations where they can thrive and “grow like wild.”
Because they have few or no natural competitors in their new territory, they can choke off existing plant varieties and spread out of control.
The usual culprit is humankind. All it takes is one person to accidentally carry a seed on the sole of his or her shoe in one country, fly across an ocean, and then inadvertently drop that seed on a different continent. Then, the “foreign plant” is off to the races!
At other times, people transport plants legally or illegally for whatever reason. This, too, is a major way in which invasive species get to places where they don’t belong.
Let’s take a look at the Top 10 invasive species of plant in the U.S. right now.
1. Bamboo
It may surprise you to know that bamboo is becoming a problem in the U.S. Most people have positive feelings about this remarkable plant because of its many uses, from making furniture to building construction. However, bamboo can grow up to three feet per day and spread outward by 20 feet. That means it easily pushes out highly valued American species.
2. English Ivy
While bamboo has become an invasive problem only recently, English Ivy has been causing trouble in the USA for nearly 300 years! It arrived here in the 1700s, sometimes brought over from Europe on purpose by British settlers who favor the ivy’s look crawling up the sides of red brick buildings.
English Ivy is easily spread by birds that carry its seeds around. This aggressive, fast-growing ivy has been known to choke off whole groves of trees. It does that by blocking sunlight that tree leaves need to carry on photosynthesis.
3. Purple Loosestrife
This plant is native to Eurasia but somehow found its way to the U.S. about 150 years ago. It has since spread rapidly to every state except Florida and Hawaii. Purple Loosestrife loves wet, swampy areas and shorelines on freshwater lakes. It has taken over wetlands and marshes while also crowding riverbanks and lakeside areas.
4. Japanese Honeysuckle
Yes, it’s lovely when it blooms pretty orchid-like white and yellow flowers. It also has a lovely scent that many people adore. That’s why they keep giving it a free pass and planting it near their houses and in gardens. However, Japanese Honeysuckle is an invader to the U.S. It’s a climbing vine that can rapidly spread and choke off the plants that belong here.
5. Winged Burner Bush
This is often confused with the American native burning bush. Winged Burning Bush bears similar bright red leaves which are valued as an ornamental plant by landscapers and backyard gardeners. That’s why some folks introduced it here. The problem is, it grows out of control and has spread widely along the East Coast of the U.S. and also Illinois.
6. Norway Maple
It’s a lovely tree that’s popular for providing shade. That’s why Europeans brought it with them to America in the 1750s. Unfortunately, its excellent shade-producing function blocks sunlight for many valued native plants. It even competes with lawns by hogging so much sunlight.
7. Blackberry Bush
Formerly known as Himalayan blackberry, the blackberry bush was introduced in the late 19th Century. It was intended for cultivation, but this species proved to be an extremely aggressive spreader and has since become a major problem, especially in the Pacific Northwest. Blackberry bush removal in Portland has become a common challenge for homeowners wanting to better maintain their properties.
8. Cogongrass
The USDA tags this plant as among the most globally invasive species. It was likely brought to the southern U.S., in 1912 in the form of packing material. It was initially valued as a plant for erosion control. It soon became apparent, however, that cogongrass was a ferocious grower that can easily choke off everything around it.
9. Wisteria Sinensis
Because of its gorgeous purple-lilac-like color, Wisteria Sinensis is popular with many Americans. It was introduced here in 1916 as an ornamental plant. The problem is that it can wrap around trees and cut through bark, killing valuable trees.
10. Kudzu
Called “the plant that ate the south,” kudzu is a native plant of China, Japan and India. It has grown absolutely out of control, especially in Deep South states like Georgia and Alabama. It got a free pass to enter the U.S. in 1876 when it was introduced at the Japanese pavilion at the Philadelphia Centennial Exposition.
Conclusion
Note that many of the “worst offenders” among invasive species are highly valued by those who brought them here, and the local dealers who continue to sell them. For example, cogongrass is easy to buy from many nurseries, garden centers, and the like today.
Thus, dealing with invasive species is a complicated problem with no clear consensus for a solution. For hundreds of years, dealing with invasive plant varieties in the U.S. has remained a significant issue for plant specialists and other environmental professionals.
