Landscapes

Over the past decade, there has been an increase in the growth of invasive plant species in the U.S. due to international trade and travel. This is already becoming a major ecological problem because these plants can quickly take over large areas and crowd out native plants.

Many experts believe that these invasives were primarily planted in landscapes and gardens but can escape. This being said, homeowners must be educated about all these plant species, which can cause potential harm on a larger scale.

In this article, I have listed 28 invasive plants that you should skip buying if you are starting your garden. This is essential if you want to beautify your yard without posing a threat to our environment. I have also included some valuable tips on getting rid of them if they get out of hand.

What are Invasive Plants?

As opposed to native plants, invasive plant species are considered aliens or not indigenous in a particular area where they are seen to be growing. They are labeled as such because they tend to spread like wildfire, and they can cause harm to both our environment and economy.

Since these plants are usually pretty at first glance, most people purchase them to include in their landscapes. While this is not strictly prohibited, one should always consult a landscape professional before growing these alongside native plants because they may cause monoculture in the long run.

If you are interested to know why these invasive plants are indeed so invasive, the answers are both easy and complicated. There are no diseases or insects that plague these plants in their new homes as compared to where they originated, so they have free rein.

Another factor that helps these invasives grow faster than other plant species are underground root networks like rhizomes. By definition, rhizomes are stems that grow underground in a horizontal manner. They produce new roots from their nodes, so they aid these unwanted species’ production.

Impacts of Invasive Plants

To fully understand why you should avoid planting invasives at all costs, let me share their impact from a small scale to a larger scale. Here’s how they affect your landscape, the economy, and the environment:

Landscaping Impacts

• Invasives cause extra work for gardeners.
• They tend to displace plants that are more difficult to grow.
• They lessen one’s enjoyment of seeing a landscape.
• They may cause trouble with the neighbor, especially if they also invade their area.

Environmental Impacts

• Invasives do not provide strong root structures to bind the soil, so erosion is possible during constant flooding.
• Invasive plants are one of the leading causes of biodiversity loss since they displace native plants.
• They outcompete plants that serve as food and cover for some wildlife animals.
• They reduce the growth of trees because they can prevent the sunlight from reaching the seedlings.
• They weigh down trees, so they become easier to blow down.
• They create fuel for unexpected wildfire.

Economic Impacts

• Invasives decrease land’s value.
• It hinders agricultural and fishing productivity.
• The cost for controlling their growth is not exactly cheap.
• Livestock can be forced into sub-optimal and marginal lands.

Social Impacts

• The options for livelihood can be narrowed since lands that should be used for productivity are dominated by invasives.
• The use of land for recreational purposes is limited.
• Some invasives pose a risk to human health.

29 Worst Invasive Plant Species in the United States

When we visit plant nurseries, we are often drawn to the aesthetically appealing ones. We excitedly bring them home and include them in our gardens, not knowing that they can cause problems in our whole landscape.

Some invasive plant species in this list are exactly like that. They look really desirable and pretty on the outside, but their true nature becomes apparent after a while.

Several plants in this list are considered native in one region and extremely invasive in another. Do not be confused, and do further scientific research on each plant if you want to know more about them.

1. Purple Loosestrife

Scientific name: Lythrum salicaria

Purple Loosestrife is an invasive plant species that originated in Europe and temperate Asia. They were first introduced in the U.S. in the early 1800s to serve as medicinal and ornamental plants.

Since it arrived in North America, Purple Loosestrife has seriously invaded roadsides, wetlands, and disturbed areas. To give you a picture of how uncontrollable they are, each plant can grow up to 30 flowering stems that can release 2.7 million seeds into the earth each year.

In an effort to eradicate them, both the American and Canadian governments released two European beetle species, which are natural enemies of Purple Loosestrife, in the year 1992.

2. Japanese Honeysuckle

Scientific name: Lonicera japonica

Japanese Honeysuckle traces its origin to Eastern Asia, specifically Japan, China, and Korea. They were brought to North America in the late 1800s to help with soil erosion and wildlife cover.

Unfortunately, this species is now considered invasive because it can adapt to different environmental conditions, and they compete with whatever plant there is in the area by producing toxic chemicals. They are very aggressive that they are commonly found in roadsides, forest edges, fields, and floodplains.

Since birds usually eat their fruit, they spread fast and form dense patches.

3. Japanese Barberry

Scientific name: Berberis thunbergii

This invasive shrub from Japan was introduced in the U.S. as an ornamental plant in the 1800s, is now very detrimental to many forest lands found in the Northeast. 

It dramatically impacts agriculture due to being hosts of black stem rush, a disease that can cause significant damage to grains. It can also shade out all the native species in a forest, even the undisturbed ones.

This plant is densely thorned and is commonly spread by birds. If not prevented from growing, they have the ability to invade native lands, lessen wildlife habitat, and restrict different forms of recreational activities.

4. Norway Maple

Scientific name: Acer platanoides

Similar to the invasives formerly discussed, Norway Maple is able to spread quickly. This is a native plant in Europe that was introduced in the United States in the year 1756.

Since this tree is very much adaptable, it is planted everywhere to provide shade. However, as time progresses, this has proven to be a dominant species since it tends to displace native trees, especially in the Northeast and Northwest.

This tree’s common victims are the native maples and some wildflower species.

5. English Ivy

Scientific name: Hedera helix

English Ivy is an evergreen groundcover brought to the U.S. in the early 1700s by European colonists. It can crowd out weeds in a landscape, and it also looks extremely pretty, so most homeowners fall for their charm.

Many aren’t aware that English Ivy can also be quite destructive since they can completely cover and topple trees, and they can supplant native plant species in a forest. They are so vigorous that they are already considered seriously problematic in the Pacific Northwest.

6. Kudzu

Scientific name: Pueraria Montana

The Kudzu vine belongs to the pea family, but if you expect them to be a normal type of crop, you’ll be disappointed.

This invasive species was introduced by Japan to the U.S. in 1876 at the Philadelphia Centennial Exposition. Initially, it is known to be an ornamental plant and a forage crop. 

The Soil Conservation Service even planted a million acres of Kudzu from the 1930s to 1940s to eradicate soil erosion. Eventually, they realized that this plant grows one foot a day. This means that they can easily kill trees by toppling and girdling them.

7. Chinese Wisteria

Scientific name: Wisteria Sinensis

Wisteria Sinensis, or Chinese Wisteria, is another flowering plant from the pea family. It has been growing in the U.S. since 1916 and is widely known to be an ornamental plant.

There are currently 19 states in the United States that find this plant invasive. Its woody vines can quickly be established, whether in full or partial shade.

There is evidence that it can climb shrubs, trees, and even manmade structures. Their vines twine around their hosts, which causes destruction in just a matter of time.

8. Butterfly Bush

Scientific name: Buddleia davidii

Butterfly Brush is an attention-grabbing plant commonly found in home landscapes. However, no matter how helpful this shrub may look for butterflies and other types of pollinators, we cannot run from the fact that it is very invasive.

This species usually escapes cultivation and wreaks havoc among natural areas. It is time-consuming to remove them, and in some cases, it is impossible to pull them out.

Several states have already banned this plant’s propagation, and they really should since this can rapidly invade riverbanks, open fields, and reforested areas.

9. Black Locust

Scientific name: Robinia pseudoacacia

This tree which is a native of Pennsylvania is causing problems in Massachusetts, Connecticut, and Maine. They were once purposefully planted in the Midwest, Texas, and West Coast in the hopes that they can control erosion and fix the soil’s nitrogen level.

Right now, this invasive species spread rapidly through stump sprouting and root suckering. It forms dense colonies which shade most forest openings and prairies, which lead to the death of native vegetation.

This tree’s bark, seeds, stem, and leaves are very much poisonous to horses.

10. American Bittersweet

Scientific name: Celastrus scandens

This type of climbing vine tightly twines itself on its support, whether it is a shrub, a tree, or a masonry structure. Do not mistake this as the Ornamental Bittersweet because they are far from being the same.

The American Bittersweet produces an autumn fruit that many people find attractive because of its yellow-orange color. However, this crimson-berry like fruit should not be consumed by humans because it’s highly toxic.

Aside from bearing a toxic fruit, American Bittersweet can grow out of control on abandoned buildings and roadsides. They are capable of taking over an entire landscape in just a matter of months.

11. Japanese Knotweed

Scientific name: Polygonum cuspidatum

This invasive plant species, a member of the buckwheat family, was first popularized in the U.S. in the late 1800s. It was then used as an ornamental and erosion control plant.

The funny thing is, during the 1930s, this plant is even sold in various catalogs, even though many people know that it is problematic to include it in a landscape. 

It can grow up to 15 feet tall, and its stems resemble that of bamboo. You’ll often see this invasive in old farmsteads and homes, low-lying areas, and near streams and rivers.

12. Common Buckthorn

Scientific name: Rhamnus cathartica

This can be called a small tree or a large shrub since it only grows up to six meters. Its leaves are egg-shaped, and they’re dull green in color, so it’s pretty easy to identify.

It was said that this invasive species was introduced to North America from Europe in the 1800s as a windbreak and ornamental plant. But in the 1900s, it was discovered that it forms thick hedges, preventing native plant and herbaceous species regeneration.

Viable seeds can remain in the soil and sprout for up to six years, so they are tough to eradicate.  There are concerns that the Buckthorn is changing the fuel characteristics of forests, increasing the likelihood of forest fires.

13. Dame’s Rocket

Scientific name: Hesperis matronalis

Dame’s rocket used to be a garden favorite, but it is now considered a lethal plant that can rapidly invade private and surrounding landscapes.

How does this plant disperse uncontrollably? They have seed-bearing pods that can pepper seeds to many wildlife, which they then carry across different places.

Because this plant grows extensively, it can infiltrate waterways, tree lines, farm fence rows, and wetland margins. This invasive plant also colonizes most natural areas like savanna, prairie, and streams.

14. Burning Bush

Scientific name: Euonymus alatus

This shrub native in Asia has long been popular in the United States as an ornamental plant. The flame-red foliage and the red berries it produces during the fall are stunning; that’s why many homeowners include this in their landscape.

Despite its beautiful appearance, Burning Bush can effortlessly displace native species in any area because they grow rapidly and can reach a height of 20 feet.

Another issue about this plant is that the berries they produce often drop and reseeds. Eradicating them is hard since birds also carry these seeds to other areas.

15. Giant Hogweed

Scientific name: Heracleum mantegazzianum

Giant Hogweed is a perennial which belongs to the carrot family. This is originally an ornamental plant from Southwest Asia, but it is now naturalizing in some parts of North America.

According to most reports, this invasive species commonly grows along ditches, streams, and roadsides. It also invades other areas like old fields and woodlands.

What’s more alarming about this plant is that they often cause soil, rocks, and other stream banks’ materials to fall in the water. This threatens species living in the streams, so many states have already banned them from being planted.

16. Bamboo

Scientific name: Bambusa vulgaris

If you want some sort of privacy plant that can shield your property from your nosy neighbors, you may have thought of raising bamboos.

Unfortunately, this is not recommended since this giant grass is one of the most invasive plants in the U.S. Yes, its slender form and the shade it provides seem suitable for urban areas. But trust me, when they start growing roots in your property, they are incredibly uncontrollable.

They can grow up to 20 feet and form clumps in just a matter of months. If you have them spreading on your property, you may want to call a professional to get them under control as the roots are very aggressive and far-spreading.

17. Winter Creeper

Scientific name: Euonymus fortunei

Winter Creeper is an evergreen perennial from Japan, China, and Korea. It was initially introduced in the U.S. as an ornamental plant, but it is now causing significant land damages in various states.

This vine is reported to invade forest margins and openings. It can grow across the ground, killing herbaceous plants and climbing trees by clinging to their bark.

Like all other Euonymus plants, Winter Creeper is also poisonous when eaten in large amounts. However, since they are not that toxic to birds, they eat this plant’s berries and scatter their seeds to various places.

18. Sacred Bamboo

Scientific name: Nandina domestica

This plant species, also called heavenly bamboo, is not really that “heavenly.” It used to be an ornamental plant in most landscapes, but after a few years of being brought to the U.S., this small shrub has managed to escape and invade forest interiors as well as their edges.

Historically speaking, this plant came from Asia and reached North America during the early 1800s. It is seen invading forests located in the Southeast U.S. due to its ability to be shade tolerant.

19. Chinese Privet

Scientific name: Ligustrum sinense

Chinese Privet is a type of semi-evergreen shrub which was introduced to the U.S. in 1852. It is a native of Europe and Asia, and it grows up to 20 feet tall.

Because there are many privet species that currently exist, distinguishing them from the others can be difficult. It can create dense thickets which can invade riparian sites, fields, fencerows, forest understories, and roadsides.

Aside from this, they can shade native plants and reduce tree growth.

20. Autumn Olive

Scientific name: Elaeagnus umbellata

Autumn Olive is a woody plant brought to the United States in the 1800s. This used to be viewed solely as an ornamental species, but it was later used to provide cover and food for wildlife and prevent soil erosion.

Currently, this plant brings major hassle instead of strengthening erosion control. It grows uncontrollably in grasslands, meadows, roadsides, and forest edges, where it quickly displaces the native plants.

The Autumn Olive’s roots allow this plant even in unfavorable soils. When this plant grows, it can produce 200,000 seeds from a single plant yearly. Unfortunately, cutting or burning Autumn Olive’s only propagates them more.

21. Bradford Pear

Scientific name: Pyrus calleryana

An article published by the Washington Post headlined, “Scientists thought they had created the perfect tree. But it became a nightmare” the existence of Bradford Pear as an invasive plant was discussed in detail.

Initially, the U.S. Agriculture Department scientists label this plant as a rootstock for the common pear. However, in the late 1990s, its invasive tendencies progressed’ Right now, it is already tagged as a weed in 19 states.

Birds disperse the seeds of this tree. They can easily invade open spaces like woodlands, pasture, and grasslands by forming dense thickets. Its flowers also produce a foul smell which can be compared to that of a rotting fish.

22. Common Periwinkle

Scientific name: Vinca minor

Common Periwinkle, a vine-like plant that can also trail groundcover, traces its origin from Europe. It is introduced in North America as an ornamental species during the 1700s, but it managed to escape cultivation and invade most natural areas in some parts of the Eastern U.S.

Since this plant likes shady areas, forests and old homesites are often their target. Periwinkles form extensive and dense mats, which quickly displace woody plants and native herbaceous species on the forest floor.

The only good thing about this invasive is that it can be pulled by hand, raked up, or dug up. However, it is not suggested to mow areas with Periwinkles because it doesn’t help eradicate them.

23. Princess Tree

Scientific name: Paulownia tomentosa

This invasive plant species also goes by the names Foxglove Tree, Royal Paulownia, and Empress Tree. It was originally from Central and Western China, but the Dutch East India Company then brought it to Europe and America in the 1830s.

As per historical records, the Princess Tree was initially used for timber, ornamental, and medicinal uses. It is also highly-priced back then because it can be used for carving.

Currently, this tree is invading stream banks, forests, and rocky habitats in the Eastern part of the United States. It can sprout prolifically, and it can survive cutting, fire, and even bulldozing. What’s more, it can adapt to a wide variety of environmental conditions like drought and the existence of acid or infertile soil.

24. Sweet Autumn Clematis

Scientific name: Clematis terniflora

Do not be deceived by the good looks of this plant because this can quickly overwhelm your landscape. 

Sweet Autumn Clematis or Sweet Autumn Virginsbower came from the Buttercup family. It is a native plant of Japan and China, but it reached U.S. lands as an ornamental vine being sold in nursery trade. The flowers it produces are white, and its leaves are usually compound three leaflets.

Today, Sweet Autumn Clematis is invading the Eastern United States, particularly forest edges, streams, and roads. It grows a dense form blanket that blocks the sunlight for other vegetation.

Curious as to what exact states consider this plant invasive? They are Virginia, Tennessee, Alabama, Delaware, Illinois, Georgia, Florida, New Jersey, Maryland, North Carolina, and South Carolina.

25. Weeping Lovegrass

Scientific name: Eragrostis curvula

Weeping Lovegrass is a type of perennial bunchgrass that rapidly grows, especially during the warm season. Its leaves are droopy, and the tips are almost reaching the ground, so they are called “weeping.”

Historically speaking, Weeping Lovegrass is a native plant of Southern Africa, but it was brought to the U.S. soil and has since established its roots in many areas.

Often, you’ll see this invasive grow in forest communities, chaparral, woodland, and roadsides. It is especially keen on growing on burned sites as well.

26. Japanese Spirea/Japanese Meadowsweet

Scientific name: Spiraea japonica

Japanese Spirea targets various habitats in the Eastern United States, including forests, fields, stream banks, and other disturbed areas. This is an invasive shrub that can grow up to six feet or 1.8 meters tall.

During the late spring, Japanese Spirea produces attractive clustered pink flowers at its branches’ tips. Although this is something that might convince you to purchase this plant from nurseries, I suggest that you skip doing so because it can displace other plants in your landscape.

You should also know that it spreads rapidly in natural areas because it quickly escapes our landscapes. Surely, you don’t want to cause damage in your community.

27. Ajuga

Scientific name: Ajuga reptans

The Ajuga plant, which is also called Bugleweed or Carpet Bugle, is a wide spreader. It is quite long-lasting as it can tolerate a wide variety of soil conditions.

If you are planning to add this to your landscape, think again. It can be hard to control this plant species because it spreads through stolons and rhizomes. This is highly problematic, primarily for small perennials and annuals.

Another thing to note about this plant is that it can spread by long runners. It can easily escape boundaries and invade your neighbor’s lawns and flowerbeds.

28. Lantana

Scientific name: Lantana camara

This plant which is still being sold in most nurseries in the United States, poses a major ecological threat by forming dense thickets. It is not recorded when this perennial shrub reached the U.S., but one thing is for sure, this is causing headaches to countless homeowners.

According to Texas Invasive Species, this plant has oval leaves which can be yellow-green to green in the shade. It produces tubular flowers, which can vary in coloration.

Like other invasives, this plant species can dominate plantations, orchards, and forest communities. It is also considered a significant pest in Florida since it reduces crop vigor and productivity.

Aside from all these, Lantana’s leaves and unripe fruit are poisonous to children and livestock.

29. Garlic Mustard

Scientific name: Alliaria Petiolata

This invader looks innocent enough with its pretty little white flowers on tall green stems, but don’t let it fool you.  Once it invades your yard, it is very difficult to eradicate.

Garlic mustard is considered a class A noxious weed.  It typically stands about 2-3 feet tall with scalloped, kidney-shaped leaves.

It spreads by seeds and is a self-pollinator. This means that one plant can end up overtaking an entire area, and a stand of these plants can produce 62,000 seeds per square meter.  It also produces chemicals that inhibit the growth of other plants. 

It can rapidly displace native species in forests and along riverbanks and has filled many unsuspecting back yards before the homeowners even realized it was happening.

It originally came over from Europe as a food plant.

3 Tips on How to Get Rid of Invasive Plants

Removing invasive plants in your landscape is not something you should put off since this would have significant impacts on the environment and economy once they are able to escape your yard. This being said, here are some tips to successfully rid your yard of these unwelcome plant species:

Tip #1: Research

Before you do anything on the shrubs, vines, or trees that are growing uncontrollably in your garden, make sure that it is indeed an invasive species. You might be removing an endangered plant, for all you know.

Tip #2: Remove invasives using the appropriate method

Here are some of the methods you can utilize in removing invasive plant species in your landscape:

• Pulling and Digging: If the invasive plant is still present in a limited number, you can pull and dig them out in the traditional manner. However, you have to ensure that you remove the plant’s root system because this is the leading cause of its propagation. It can be a daunting task, but sometimes brute for is the only way to go.
• Biological Method: This uses insect predators or plant diseases to target certain plant species. 
• Cutting or Mowing: By cutting or mowing, you interrupt the plant’s photosynthesis process since the leafy materials are removed. If you have invasives in an area that can be moved, this is often the easiest method.
• Suffocation Method: You can put a UV-stabilized plastic sheet over the area affected by the invasives and leave it for two years. Yes, you read it right, two years! When you remove the plastic, the plant underneath will surely be dead after that span of time.
• Chemical Method: Using herbicides is one of the most effective methods in removing invasive plants in your garden. However, you first have to consult your state’s rules regarding herbicide use.
• Organic Method: This method is all about experimenting with natural ways to kill invasives. Some standard techniques use vinegar as a herbicide alternative and watering plants with boiling water. 

Tip #3: Replace

Getting rid of the invasive plant in your landscape doesn’t end in removing it through the various methods I discussed in my previous tip.

You should also replace the holes the plant left so it can no longer establish its roots in your soil. To find suitable replacements, you can check out various articles on the web, or you can seek the help of expert gardeners.

It would be better to find a native plant to replace the invasive you removed because this is relatively easy to grow. However, if you want something similar in appearance to the invasive, there are tons of options to choose from. You have to invest time researching and visiting plant nurseries.

Final Thoughts

If you’re feeling unsure about beautifying your garden because of all these invasive plants you have to be cautious of, hear me out. The very reason why I wrote this article is to guide you in identifying them.

Now that you know all the 29 invasive plant species in the United States, you wouldn’t unknowingly buy them from plant nurseries. You’ll be more careful in choosing the plants or trees to include in your garden, which significantly contributes to our ecological balance.

It is possible to upgrade your landscape without causing harm to our environment. That is if you will tick off the invasives in your list. There are so many alternatives available, and you can easily access a list of them through a bit of web research.