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Are Non-Native Plants Always Invasive Plants?
It feels like non-natives and invasives are buzzwords in the gardening industry. So, you may be wondering if these words are interchangeable.
Does non-native mean the same thing as invasive? The quick answer to your question is no. There is a difference between a non-native plant and an invasive species! All invasives are non-natives… but not all non-natives are invasives!
First, lets understand what a native plant is. Native plants feed and shelter native animals and insects and support a healthy ecological web of life. Basically, native plants are ones that naturally grow in your area and were not brought in from other regions… or even other countries or continents.
Quick Tip: If you’re looking for more expansive definitions of native, non-native and invasive plants you should check out this article first.
The difference between non-native and invasive plants
Non-natives, also called exotic or introduced plants, have been brought into your region from somewhere else and then become established. Just being a non-native plant does not necessarily mean that it’s an invasive plant! In fact, most of them aren’t. Many non-natives have a neutral or even positive effect on the ecosystem.
A great example of this is the hosta… which many gardeners are familiar with. Actually hosta is the genus name for this group of plants, which includes approximately 70 species. BUT– did you know that hostas are not native to the United States or even Europe!? They are native to northeast Asia (China, Japan, Korea and the Russian Far East). Does that make them invasive? Nope.
The same goes for garden hydrangeas, boxwoods, tulips, daffodils, garden salvias, dwarf shrub junipers, peonies and many others! These plants are non-native to USA but not considered invasive.
An invasive plant is a non-native plant that negatively impacts the region where it’s been introduced. Invasives can threaten native biodiversity as well as the economy and/or society, including human health. In fact, invasive species have been identified by the International Union for Conservation of Nature (IUCN) as the second most significant threat to biodiversity… right behind habitat loss.
Here are just a few examples of plants known to be invasive. Please note that this is nowhere near an exhaustive list.
- Japanese Honeysuckle (Lonicera japonica) – an aggressive vine that smothers, shades and girdles other competing vegetation. Many of the birds eat the fruit of this plant, thereby spreading the honeysuckle’s seeds.
- Native to Eastern Asia, brought to the USA through Long Island, New York in 1806.
- Invasive throughout the eastern USA from Maine to Florida and west to Wisconsin and Texas, with scattered occurrences in the Southwest.
- Japanese Barberry (Berberis thunbergii) – a heavily fruiting shrub that forms dense thicket, crowding out native plants. Barberry seeds are easily spread by birds.
- Native to Japan, brought to the USA in 1875 through Boston, Massachusetts from Russia.
- Invasive throughout the northeastern USA from Maine to North Carolina and west to Wisconsin and Missouri.
- Winged Burning Bush (Euonymus alatus) – remains very popular and widely sold, this invasive forms dense thickets that displace many native plants. Burning bush spreads through vegetative reproduction and to new areas through bird dispersal of seeds.
- Native to Northeastern Asia, Japan and Central China. Introduced to the USA around 1860.
- Invasive throughout New England to northern Florida and the Gulf Coast and also in Illinois.
By the way, trees, shrubs and plants aren’t the only species that can be classified as invasive. There are also many invasive animal species that are a threat to ecosystems around the world.
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Why do some plants become invasive?
You may be wondering why some non-native species become invasive and other do not?
In it’s simplest form… some non-native plants become invasive because when non-natives are brought into the region, the insects, disease, predators and other natural controls that would prevent it from becoming invasive in its natural habitat do not come with it. So, the plant has no threats. Because there’s nothing to “compete” with, it thrives and takes over.
Are invasive plants considered invasive everywhere?
It’s important to point out that non-native plants can become invasive in one region, but not invasive in another. This makes things trickier, doesn’t it?
The reason for this nuance is that the invasiveness of the plant depends on whether or not their “new environment” contains any natural predators or pests that can keep the non-native in check. If there are natural predators or pests, the non-native may not be invasive in a particular region. But, if the non-native is able to reproduce and grow rapidly because there’s not any competition… that’s when it will be invasive.
Why are invasive plants dangerous?
When an invasive plant takes over many problems can occur. One of the biggest issues is that these plant species may not be a viable food or habitat source for local animals and insects. And when that invasive plant has choked out or taken over the food and habitat that these animals and insects need to survive… they can’t live there anymore. Then the animals that feed on those animals are affected… and so on. It creates a chain reaction that negatively impacts the entire ecosystem and biodiversity of the region.
Can native plants be considered invasive?
Some native plants seem to really spread and take over… so you may be wondering whether or not native plants can be classified as invasives.
The answer is no. The term “invasive” is reserved for non-native plants only. While there are certainly some natives that are more aggressive than others, they are not referred to as invasive species.
So what are these more aggressive native plants called, then? Well… aggressive is one word you can use. Some gardeners call these more aggressive natives “thugs”… which is clearly a slang term but it may help you to talk about more aggressive native plants in an easier way! Plus, thug is kind of fun to say, right?
How do I know if a plant is invasive?
You’lll have to do your research in order to determine whether a particular plant is invasive in your area. A great place to start your research is on the USDA website’s Introduced, Invasive and Noxious Plants page.
You can also find a State and Master Gardener Extension Program near you so you can talk to an expert in your particular region.
In addition, most state government websites will also have regional resources available to you. Check for the .gov at the end of the domain name for these resources.
Wrapping Up
I hope that this article cleared up some of the misconceptions and confusions surrounding non-native and invasive plant species. Remember that just because a plant is non-native does not mean that it’s invasive. And just because a plant is invasive in one particular region, does not necessarily mean that it’s invasive in another region.
So, you’ll have to be a really diligent gardener and learn as much as you can about your local area. That way you’ll be able to make confident plant choices that won’t disrupt the natural ecosystems and biodiversity of your region.
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Amy Fedele
Amy is the founder of Pretty Purple Door and has been a garden designer since 2014 and graphic designer since 2005. She helps home gardeners design their own beautiful landscapes that are colorful in all four seasons, show off your personality and suit your lifestyle. Amy's work has been featured in publications like The Spruce, Family Handyman, Buzzfeed, Country Living Magazine and more. Read full bio.