Garlic Mustard Garlic mustard harms native plants by outcompeting ephemeral spring wildflowers for sunlight and resources. © Lemanieh/Getty Images
It’s a sunny early spring day in southern Ohio. The trees’ still bare branches sway in a slight breeze and sunlight illuminates the forest floor. There, bright yellow flowers have emerged, carpeting the ground between the trees. Some of the woody shrubs already have leaves, bright green and shimmering.
At first glance, this would seem to be an almost idyllic nature walk. But for ecologists, land stewards and conservationists, it’s far more worrying than serene.
That’s because those blooming bright yellow flowers are lesser celandine and the leafed-out shrubs are Amur honeysuckle—both invasive species. And they’re just two examples of many species that are a huge problem for Ohio’s indigenous wildlife, plants and natural areas.
What is an Invasive Species?
Invasive species are nonindigenous plants, animals and microbes that are causing ecological harm by living outside their historic, native range where they evolved to their present form. In their original home ranges, these species have constraints on their ability to spread, such as predators, food availability and other competitive species.
However, once they’re outside their home range, those natural limits are reduced or disappear entirely, giving the invasive species a huge advantage over native species that still have those constraints within their environments.
As a result, invasive species can cause serious damage to Ohio’s natural areas and the animals and plants that live within those spaces. And it’s not just land-based ecosystems that are at risk—Ohio’s waterways are just as vulnerable to invasive species.
A Quick Glossary
There are a lot of confusing terms when it comes to talking about invasive species and what it all means, so here’s a quick guide to keep in mind.
Native or Indigenous: These are plants and animals that originated and developed within a habitat and are adapted to that ecosystem.
Non-native or Non-indigenous: These are plants and animals that are living outside of their home range, but they are not causing harm to the ecosystem where they are now found. That said, even though non-native species may co-exist well with native species, they still may not be as beneficial to a habitat as a native species would be. For instance, a non-native flower may not harm the surrounding habitat, but its pollen or nectar might not be as accessible to native bees as a native wildflower’s is.
Invasive: Non-native plants or animals that harm the environment and/or the economy are considered invasive. These non-native species can also hurt the health of people, animals or plants as they spread aggressively and take over the natural areas where they are now found.
It’s important to research and review any new plants you introduce to your yard or properties—even those found in local plant nurseries or stores can be problematic. Always plant species that are native to Ohio if you can and make sure that any non-native plants are not likely to spread outside of your yard or habitat. Check out some of our resources listed at the end of this page for more information on native and invasive plants in Ohio.
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What is The Nature Conservancy Doing about Invasive Species?
There isn’t just one answer or one solution to the threat of invasive species in Ohio. That’s why TNC's invasive species work in Ohio extends across a variety of disciplines throughout the state. In general, we tackle invasive species by focusing on three overarching practices:
Preventing the introduction of non-native invasive species
Detecting and responding to populations of invasive species in natural areas
Protecting and restoring native habitats, including efforts from planting native plants to large landscape-scale restorations
While these strategies can take years to show consistent results, our conservation staff and partners know that even with just a little help, nature is resilient and native habitats can flourish after invasive species are removed, given time and careful stewardship.
Our Work to Mitigate Invasive Species
Active Land Management
TNC staff, volunteers and partners actively control invasive species at our Ohio preserves through a range of methods including hand pulling, herbicides, mowing, mulching, prescribed fires and more.
A good example of this is our work against hemlock wooly adelgid (HWA) and elongate hemlock scale (EHS), tiny invasive insects that threaten the Eastern hemlock trees at Morgan Swamp Preserve. These trees are a keystone species in this part of Ohio, creating environments that a variety of plants and wildlife depend on.
However, both HWA and EHS feed on hemlock trees causing damage, stunted growth and even tree death. TNC is working alongside partner organizations to survey and treat populations of hemlocks for HWA and EHS throughout northeast Ohio to ensure hemlocks can continue supporting a rich diversity of native understory plants and a plethora of wildlife.
Best Practices
Our land managers and volunteers use best management practices, or BMPs, to prevent the spread of invasive species. Examples include properly cleaning equipment after working in an area infested with a problematic species and limiting soil disturbance in our natural areas.
Partnerships
The Nature Conservancy works every day to detect, control, eliminate and prevent invasive species throughout Ohio. But we don’t do it alone—we partner with diverse groups and volunteers throughout the state, lending our knowledge and skills to help partners identify and control the spread of invasive species everywhere they appear.
Invasive Species in Ohio
Invasive Plants
According to the Ohio Department of Natural Resources, about 22% (around 500 species) of vascular plants (like grasses, trees or wildflowers) are non-native to Ohio. That seems like a lot, but the good news is that many of these plants are not invasive. Even though they aren’t indigenous to Ohio, they do not stray too far from where they were introduced and do not displace native plants within their habitats.
There are about 100 non-native plants that are considered problematic in Ohio. These plants are extremely harmful to our native plants, natural areas, agriculture and wildlife. Some, like wild parsnip or poison hemlock, can be detrimental to human health, too.
Invasive or Native?
Two of these plants are native to Ohio, but the rest are invasive. Can you spot the native species?
Callery Pear
INVASIVE!
Native to Asia, callery pear (Pyrus calleryana) was brought to North America for use as an ornamental tree in landscaping. It was a highly prized tree, due to its beautiful, abundant white blooms in the spring and its fiery red foliage in the fall.
Originally, the tree was thought to be sterile and therefore not a danger to surrounding natural areas and ecosystems. However, these trees can cross pollinate between different cultivated varieties (cultivars) and, as result, it began to quickly spread outside of the landscaped yards and properties where it was planted.
Today, it's easy to spot callery pears almost everywhere you go in Ohio along roadsides and in natural areas—a testament to their ability to spread and colonize just about any type of soil and habitat.
Because callery pears are able to grow and spread rapidly, they can take over prairies, grasslands, woodlands, and other natural areas, forming thickets that crowd out native species. Once established, they can cause a rapid change in native plant and wildlife communities, damaging and disrupting otherwise healthy habitats.
Due to their invasiveness as of January 1, 2023, it became illegal to grow, buy or sell callery pear trees in Ohio.
Wild Parsnip
INVASIVE!
Wild parsnip (Pastinaca sativa) grows in prairies, oak savannas, fields, pastures and other open or disturbed areas. It's an adaptable and fairly hardy plant, growing well in both dry and wet soils. It can be found throughout most of the United States due to its rapid growth and spread.
Wild parsnip is in the carrot family and grows two to five feet tall in its second year. It flowers in a small flat compound of several small yellow blooms. In fact, it looks very similar to its close relative, Queen Anne's Lace, which has white blooms instead of yellow.
The stem, leaves and flowers of wild parsnip contain chemicals that can increase skin's sensitivity to sunlight and cause rashes or blistering.
Goldenrod
NATIVE!
Although goldenrod species are incredibly common and found everywhere throughout Ohio, these fall-blooming plants are native to our state. Ohio goldenrod (Solidago ohioensis), Riddell’s goldenrod (S. riddellii) and bog goldenrod (S. uliginosa) can be found in wetlands, bogs, fens, meadows and fields. Goldenrod boasts both disk and ray flowers in a stunning shade of yellow. As a fall blooming plant, it’s a critical source of late season food for pollinators and provides plenty of seeds for birds once the flowers fade.
Dame's Rocket
INVASIVE!
A relative of garlic mustard, dame's rocket (Hesperis matronalis) is a biennial plant, establishing itself during one year and blooming the next. Introduced to North America from Eurasia in the 1600s, dame's rocket is found in both moist woodlands and open areas. It outcompetes native wildflowers and other plants, creating a monoculture where it grows and reducing critical food sources for native birds, butterflies, bees and other creatures.
Dame's rocket is often sold in wildflower seed packets, so check seed mixes thoroughly before planting.
Lesser Celandine
INVASIVE!
Native to Europe, northern Africa, and Asia, lesser celandine (Ficaria verna) was brought to the United States as an ornamental plant for gardens, but quickly escaped and spread into wild areas. It’s one the first plants to bloom in the spring and divides to form a thick mat along the forest floor, creating a carpet of lesser celandine.
In areas overrun with lesser celandine, native wildflowers, particularly spring ephemerals like spring beauty or trout lily, are crowded out and unable to emerge. These native plants are critical to native wildlife in the spring, particularly native bees and other pollinators that have few other food sources early in the season. Without the native spring wildflowers, populations of native bees and other wildlife begin to decline.
Spicebush
NATIVE!
Spicebush (Lindera benzoin) is an understory shrub that’s found throughout Ohio’s moist to wet woodlands. It gets its name from the spicy fragrance its twigs and branches release when scratched. Growing up to about 12 feet tall, spicebush blooms in yellow flowers in the spring, which turn to bright red berries in the fall. Wildlife—birds in particular—feed on the berries.
Purple Loosestrife
INVASIVE!
Native to Europe and Asia, the invasive purple loosestrife (Lythrum salicaria) can be identified by the magenta flower spikes that are present for most of the summer. Growing two to six feet tall, purple loosestrife thrives along roadsides and in wetlands. In the fall, purple loosestrife readily forms seeds—more than 2 million per plant. The seeds are tiny, about the size of a grain of sand, and spread easily via water, wind, wildlife and people. Purple loosestrife seeds are also incredibly hardy; while they can germinate in the next season, they can also lay dormant for several years before blooming.
Bush Honeysuckle
INVASIVE!
The term "bush honeysuckle" includes several species of invasive deciduous shrubs. In Ohio, the three most common species of bush honeysuckle are Amur (Lonicera maackii), Morrow (Lonicera insularis) and Tatarian (Lonicera tatarica).
All three of these species leaf out before other plants in the spring, shading out native understory shrubs and preventing them from growing. Bush honeysuckles tend to form dense thickets that have no other vegetation, making them essentially useless for wildlife.
Additionally, while birds will eat bush honeysuckle berries in the fall, these fruits lack the nutrients that birds need. In places where these plants have overrun native shrubs, migratory and other bird populations can be negatively impacted due to lack of adequate, nurtitious food. Compounding this, when birds do eat the fruits, they then help to scatter the seeds, spreading the plants even further.
Invasive Wildlife and Aquatic Species
While plants are the most common type of invasive species, some wildlife species, such as feral swine are considered invasive. Many of these invasive wildlife species are insects, such as hemlock wooly adelgid (HWA) and the emerald ash borer.
Ohio's waterways are just as vulnerable to invasive species as the forests and prairies. Like on land, invasive species in wetlands and water can drastically alter the native ecosystems, displacing and harming indigenous wildlife and plants. What's more, aquatic invasive species can reduce drinking water quality, damage watercraft and make water unsafe for recreation.
Like with plants, most invasive wildlife and aquatic species are introduced to Ohio accidentally, through trade and shipments from other countries. Once here, these species find their way into our environments and spread rapidly.
Feral Swine: Feral swine not only cause extensive damage to natural areas and agricultural areas, but they can carry several diseases that can be transmitted to people. © TNC
Phragmites: Non-native phragmites (Phragmites australis), also known as the common reed, is rapidly spreading and taking over habitats where native species once thrived. © Danae Wolfe/TNC
Asian Longhorned Beetle: The larvae of these beetles eat the inside of a variety of trees, weakening their branches and potentially killing the trees. © Michael Hoeweler
Zebra Mussels: Thanks to their abilities to rapidly grow and stick to just about everything, zebra mussels have spread through all five Great Lakes and the Ohio River basin. © paulmerideth.com
Sea Lamprey: Native to the Atlantic Ocean coasts, sea lampreys were introduced to the Great Lakes in the 1920s. They are parasitic and have contributed to the decline of native fish. © T. Lawrence, Great Lakes Fishery Commission
Eurasian Watermilfoil: Also known as spiked watermilfoil (Myriophyllum spicatum), this invasive aquatic plant forms dense underwater thickets that limit the growth of native aquatic plants. © Alison Fox, University of Florida, Bugwood.org
Box Tree Moth: The caterpillars of this moth can strip boxwood trees of leaves and even bark as they eat, killing the trees. © CreativeNature_nl/Getty Images
Asian Carp: In Ohio, there are four species of Asian carp that are of concern: bighead, silver, black, and grass carp. © Katoosha/Getty Images
Hemlock Wooly Adelgid (HWA): Named for the cotton-like excretions of wax that it produces, HWA infestations feed on the sap of hemlock trees and can kill a tree in four to five years. © ©Jerry and Marcy Monkman/EcoPhotography
Hydrilla: Introduced as an aquarium plant in the 1950s, hydrilla spreads easily and rapidly, overgrowing all other species and clogging waterways. © Eric Blackmore
How Can You Help?
The best way to stop invasive species is to prevent them from occurring in the first place—and that’s up to all of us. You can help protect native plants and animals by following these simple steps:
Verify that the plants you are buying for your yard or garden are not invasive. Replace invasive plants in your garden with non-invasive alternatives. We have resources listed at the end of this page for more information on buying native plants and identifying invasive ones.
When boating, clean your boat thoroughly before transporting it to a different body of water.
Clean your boots before you hike in a new area to get rid of hitchhiking weed seeds and pathogens.
Don’t “pack a pest” when traveling. Fruits and vegetables, plants, insects and animals can carry pests or become invasive themselves. Don't move firewood (it can harbor forest pests), clean your bags and boots after each hike, and throw out food before you travel from place to place.
Don’t release aquarium fish and plants, live bait or other exotic animals into the wild. If you plan to own an exotic pet, do your research and plan ahead to make sure you can commit to looking after it.
Volunteer at your local park, refuge or other wildlife area to help remove invasive species. Help educate others about the threat. TNC in Ohio has volunteer opportunities throughout the year.
When you see an invasive species while you are out, report it through the Midwest Invasive Species Information Network.
Explore More about Invasive Species
Want to learn more about invasive species in Ohio and around the Midwest? Check out these resources!
Ohio Invasive Species Resources
- Ohio Department of Natural Resources Invasive Species Resources: ODNR offers several articles and further information on invasive species in Ohio, including identification and reporting on the status of invasive species in the state.
- Ohio Department of Agriculture: ODA lists the current plants that are designated as invasive by law in Ohio. The list contains links for each species to pages for more specific information the plants. There is also a downloadable PDF of the list available.
- Ohio Invasive Plants Council: OIPC is a coalition of agencies, organizations, and individuals throughout Ohio concerned about the introduction, spread, and control of invasive, non-native plants in Ohio's natural habitats.
Ohio Native Plant Resources
- Ohio Native Plant Month: ONPM is a nonprofit that educates the public about native plants and provides information on where to buy native plants in Ohio.
- OIPC Alternative Plant List: This webpage contains suggestions of native and non-invasive plants to plant instead of invasive species.
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Midwest Invasive Species Resources
- Midwest Invasive Plant Network (MIPN): MIPN is a clearinghouse for information on invasive species that threaten the Midwest. The network provides factsheets, educational videos, webinars and training seminars. They also host the control database described below.
- MIPN Invasive Plant Control Database: This website contains information on how to control many invasive plants common to the Midwestern United States.
- Great Lakes Phragmites Collaborative: Everything you need to know about Phragmites (reed grasses), from on-going research, to potential bio-control and determining native vs. non-native strains. The collaborative hosts great webinars every month and promotes information sharing and partnerships among those working with Phragmites across the Great Lakes.
- EDD Maps: EDD maps is a web-based mapping system for documenting invasive species sightings. You can report any sightings of invasive species to database.
- EDD Maps Tools: This webpage offers a state-level status report and listing of all reported invasive and native species sightings.
- National Invasive Species Information Center: Managed by the U.S. Department of Agriculture, this website provides selected resources from agencies and organizations that work to identify, prevent, control and eradicate invasive species in Ohio and around the U.S.
Apps to Identify Invasive Species
- Bugwood Apps from the Center for Invasive Species & Ecosystem Health: Great smartphone and tablet apps including “Landscape Alternatives to Invasive Plants”, “Forest Insect Pests”, and the EddMaps reporting app.
- iNaturalist: This smartphone and tablet app helps identify species you spot and allows you to record your sightings for a larger database.
- Seek by iNaturalist: This is a sleekier and more intuitive app that allows to you identify species and earn badges.
- PlantSnap: This app helps identify plants, flowers, cacti, succulents and mushrooms in seconds with the click of a button on your mobile device.
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