Plant Invasion: How Invasive Plants Are Impacting Nature

Plants are brought in from different countries on purpose and sometimes on accident. Bringing non-native plants into an entirely different ecosystem can have a drastic impact on that system and the flora and fauna living in that ecosystem.

Can you name a few invasive plants in your area? Everyone has some and you may have even planted some in your yard without knowing. It’s important to know and be able to identify problems plants before they take over your yard and wildlife areas.

How They Got Here

Plants have been transported around the world for hundreds of thousands of years and were originally traded for their medicinal and agricultural uses. Pleasure gardens soon became popular and these gardens once served a utilitarian purpose. They were not only beautiful and well maintained but also had many uses. As time progressed, pleasure gardens lost their utilitarian use and many plants were imported as ornamentals.

It is estimated that over 80% of the introduced woody plants in the U.S. were introduced for landscaping. These plants escaped cultivation and many are now invasive plants. An estimated 3% of invasive woody plants were introduced as both ornamental plants and for erosion control. It’s not just the U.S. either. Anywhere from 57%-65% of naturalized species in Australia are not native to the country. Many species are introduced through landscaping, botanical gardens, and seed trading.

Plants were also introduced as people began colonizing different parts of the world. White clover (Trifolium repens) was introduced to North America for the honey bees the colonists brought over to help pollinate their European crops. The French and Spanish also introduced plants to North America including peaches from Spain. People wanted plants that they regularly used back home as they were conquering the world. I supposed it’s understandable, but they had no idea how that would impact these environments.

The Impact

Not all plants that are introduced to a region become invasive. An invasive plant is a plant that has become established, can successfully reproduce and becomes dominant or disruptive to an ecosystem. Plants that become invasive usually have an advantage over native flora. They could reproduce rapidly and produce a lot of seeds. Some may have allelopathic properties in their roots that prevent plants around them from reproducing or growing. Others may lack competition, predators, or grow rapidly. Any of these properties can make a plant hard to control or eradicate and allows them to completely take over a region. Because of their advantages, they can completely wipe out all of the native flora which in turn affects the animal populations in the region.

Invasive Plants in North America

It’s important to know what plants are considered invasive in your area so you can avoid planting them and pull them out when you see them. Almost everyone has some sort of invasive plant, however, since I’m from the U.S. I’m going to cover some plants that have become a problem here.

1. Kudzu (Pueraria montana var. lobata)

Kudzu is probably one of the most well known invasive plants in North America. It was introduced in the late 1800’s as an ornamental plant and in the early 1900’s to help with erosion and help save America from the dust bowl. Kudzu grows rapidly and can create dense shade that inhibits some native plant growth. It can also completely engulf a tree and weight it down. It is a host of a few diseases and insects that impact agriculture crops including soybeans. It is more predominant in the Southeastern U.S. but has made its way up into some Northern states.

2. Autumn Olive (Elaeagnus umbellata)

Autumn Olive was introduced for erosion control, as an ornamental, and as wildlife habitat. It produces berries both edible for animals and humans. The plant can grow up to about 20 feet and displaces much of our native flora. It reproduces quickly, is hard to remove, and is spread around rabidly by wildlife. It is found throughout the eastern U.S. and in some parts of Canada.

3. Japanese Honeysuckle (Lonicera japonica)

Japanese honeysuckle is a woody vine honeysuckle introduced from Japan and Korea as an ornamental and for erosion control. It outcompetes native flora by growing very densely and shading out areas and utilizing all of the available resources. They will also climb up small trees and bushes and choke them out. Japanese honeysuck is found in the Southern U.S. and parts of the Midwest and Eastern U.S. It has been found in Canada.

4. Euonymus

There are quite a few Euonymus species both native and invasive to North America. Euonymus americanus is native but Euonymus alatus, burning bush or winged Euonymus, is native to Aisa. Winged Euonymus was introduced as an ornamental because of its attractive fall color and fruit. It can reproduce by seed, a lot of seeds, or asexually. It starts to leaf out before native flora does, keeps its leaves longer than natives, and the seeds are spread by wildlife. It is found primarily in the Midwest and along the Eastern Coast of the U.S. It is also found in some parts of Canada.

6. Tree of Heaven (Ailanthus altissima)

When you see tree of heaven you can tell it is not native to North America. It is native to China and was brought over as an ornamental plant. It grows just about anywhere, has rapid growth and reproduction, and crowds out our native flora. It can even destroy pavement and building foundations. It has allelopathic properties in its leaves which, once they fall, help keep plants from gowning around it. It can be found throughout most of the United States and Eastern Canada.

7. Garlic Mustard (Alliaria petiolata)

Garlic mustard was brought to North America as a medicinal and culinary plant. Since its introduction, it has completely dominated the understories of many forests. It can self-pollinate, send out adventurous roots that can become new plants, and can overwinter without dying back. It is hard to control and remove because of how rapidly and easily it reproduces. It outcompetes native flora and prevents anything must garlic mustard from growing. It is found throughout the Midwest and Eastern United States and is creeping west. It can also be found in Eastern and Western Canada.

8. Bush Honeysuckle (Lonicera spp.)

There’s actually a few species of honeysuckle that are not native and are an invasive plant in the U.S. Tatarian honeysuckle (L. tatarica) can be found throughout most of the Northern U.S. And through most of Canada. Amur honeysuckle (L. maackii) is found through most of the Midwest and Eastern U.S. Morrow’s honeysuckle (Lmorrowii) can be found throughout most of the Midwest and Northeastern U.S. and Northeastern Canada. These bush honeysuckles can grow from 6-20 feet tall and prefer full sun but can survive in partial shade. They were brought over to North America as an ornamental and erosion control. Now they have taken over many of our natural regions by out-competing native flora and growing in dense thickets. Native birds eat the plant’s berries and transport the seeds. However, the berries do not provide sufficient nutrition for native and migrating birds. Native honeysuckles have solid stems when cut off whereas nonnatives have hollow stems.

Control

Each plant has their own method of control. It is important to stay vigilant and try to prevent the plantings of invasive species and removal of what is already established. Control can be as simple as pulling the plant up by hand or could require special equipment and herbicides. Research what methods work best for what every plant you may be dealing with. These eight plants aren’t the only plants affecting our native environment. Learn what plants are issues in your area and try to help stop the spread of problem plants.


Sources

Invasive Species – Coming to America By Land, Sea, and Air…
Honey Bees Across America
Controlling Non-Native Invasive Plants in Ohio Forests: Bush Honeysuckle
USDA Morrow’s honeysuckle
USDA Tatarian honeysuckle
USDA Amur honeysuckle
Invasive Plants Fact Sheet Japanese Honeysuckle
USDA Japanese Honeysuckle
The History and Use of Kudzu in the Southeastern United States
USDA Kudzu
Invasive Species: Autumn Olive
USDA Autumn Olive
Winged Euonymus: An Exotic Invasive Plant Fact Sheet
USDA Winged Euonymus
Invasive Species: Tree of Heaven
Tree of Heaven: An Exotic Invasive Plant Fact Sheet
USDA Tree of Heaven
Penn State Garlic Mustard
USDA Garlic Mustard