All U.S. states deal with invasive plants, but which states have the most species to identify and combat?
To find out, Lawn Love ranked 2024’s States With the Most Invasive Plant Species.
We compared the 50 states and the District of Columbia based on 3 categories. It can be challenging to pinpoint exactly how many invasive species impact an area, so we considered the number of invasive species per state according to the USDA’s National Invasive Species Information Center (NISIC) and invasive species reports from the University of Georgia (UGA).
For example, Connecticut’s ranking at 4th place indicates it is one of the states most impacted by invasive plant species per our sources, based on these factors.
We also considered environmental characteristics, among 5 total metrics.
Explore our ranking below. To learn how we ranked the states, see our methodology.
Note: We’ve updated our title from “Creeping In: 2024’s States With the Most Invasive Plant Species” to “Creeping In: States Most At Risk for Invasive Plant Species” to better reflect our methodology. The new title emphasizes the factors considered, including invasive plant presence, climate, and regulatory membership, to rank the states most at risk for invasive species impact.
In this article
- State rankings
- Top 5 close up
- Key insights
- Expert take
- Behind the ranking
- Final thoughts: 5 invasive plants to watch out for
State rankings
See how each state fared in our ranking:
Top 5 close up
Check out the slideshow below for highlights on each of our 5 most invaded states.
Number of Invasive Plant Species (NISIC): 48 | Rank: 7
Number of Invasive Plant Species Reported (UGA): 1,695 | Rank: 1
Percentage of Sunshine: 72.5% | Rank: 4
Average Monthly Inches of Precipitation: 1.63 | Rank: 42
National Association of Exotic Pest Plant Councils Membership: 1 (Yes) | Rank: 20
Local tips: Invasive plants can worsen wildfire conditions, so you may want to consider native species and fire-resistant landscaping when revamping your Golden State lawn.
27 California Native Plants
The Best Native Plants for Your Bay Area Landscape
10 Best Native Plants for San Diego
9 Best Native Plants for Sacramento
Photo credit: Kit Leong | Adobe Stock | License
Number of Invasive Plant Species (NISIC): 50 | Rank: 4
Number of Invasive Plant Species Reported (UGA): 935 | Rank: 3
Percentage of Sunshine: 48.86% | Rank: 47
Average Monthly Inches of Precipitation: 3.48 | Rank: 23
National Association of Exotic Pest Plant Councils Membership: 0 (No) | Rank: 1
Local tips:
10 Best Native Plants for Albany
New York Invasive Species Regulations
Photo credit: Alessandro Persiani | Adobe Stock | License
Number of Invasive Plant Species (NISIC): 46 | Rank: 16
Number of Invasive Plant Species Reported (UGA): 821 | Rank: 4
Percentage of Sunshine: 58.83% | Rank: 25
Average Monthly Inches of Precipitation: 4.035 | Rank: 9
National Association of Exotic Pest Plant Councils Membership: 0 (No) | Rank: 1
Local tip:
Massachusetts Prohibited Plant List
Photo credit: Zack Frank | Adobe Stock | License
Number of Invasive Plant Species (NISIC): 47 | Rank: 10
Number of Invasive Plant Species Reported (UGA): 702 | Rank: 18
Percentage of Sunshine: 58% | Rank: 29
Average Monthly Inches of Precipitation: 3.6 | Rank: 17
National Association of Exotic Pest Plant Councils Membership: 0 (No) | Rank: 1
Local tip:
Connecticut Invasive Plant List
Photo credit: Wangkun Jia | Adobe Stock | License
Number of Invasive Plant Species (NISIC): 53 | Rank: 1
Number of Invasive Plant Species Reported (UGA): 738 | Rank: 12
Percentage of Sunshine: 60.39% | Rank: 19
Average Monthly Inches of Precipitation: 4.041 | Rank: 8
National Association of Exotic Pest Plant Councils Membership: 1 (Yes) Rank: 20
Local tips:
9 Best Native Plants for Raleigh
11 Best Native Plants for Durham-Chapel Hill
Photo credit: Jason Schronce | Adobe Stock | License
Key insights
North Carolina (No. 5) fights against the highest number of invasive plant species, 53, according to the National Invasive Species Information Center. Virginia (No. 7) and Kentucky (No. 9) follow closely with 52 and 51 invasive species, respectively.
Not all non-native species are classified as invasive. However, non-native plants can be dormant for hundreds of years before becoming invasive and wreaking havoc on the environment. Most dormant invasive plants take an average of 40 years to become an issue.
According to tracking data from the University of Georgia, 1,695 invasive or non-native plant species have been mapped in the California (No. 1) wilderness, the most in our ranking. Florida (No. 6) follows closely with 1,509 species reported and has also been invaded by numerous animal species. These 2 sunny states also have optimal weather conditions for many species — native or not — to grow and spread.
Expert take
It can be very difficult to keep invasive plants at bay, especially when they’re for sale at nurseries across the country.
We turned to a panel of plant experts to learn more about non-native and invasive species, and what we can do to stop their spread. Read their insights below.
- Are all non-native plant species bad for the environment? Why or why not?
- What are 3 of the main benefits of landscaping with native plants?
- What are 3 considerations to take before landscaping with non-native plants?
- What are 3 misconceptions about invasive plants?
- What are 3 invasive plants in the U.S. to watch out for?
- What is 1 way people can help stop the spread of invasive plant species in their area?
- What, if anything, can local or state governments do to reduce the impact of invasive plants?
Are all non-native plant species bad for the environment? Why or why not?
The biggest concern with introducing non-native species is the potential that they’ll become invasive. Invasive species by definition are ones that harm ecosystems — typically by outcompeting native plants and reducing the resources available for pollinators, birds, and other wildlife. Some invasive plants also change how an ecosystem functions, for example by using a lot of water or fueling fires.
Not all non-natives become invasive, but depending on where you live, up to 20% of non-native plants could become invasive. So there’s a pretty high risk — especially for new plant imports that we don’t know a lot about.
What are three of the main benefits of landscaping with native plants?
I think there are two big benefits.
1. First, there’s very little risk of introducing a harmful invasive species. Native plants have evolved alongside each other for thousands of years, so the risk of one suddenly taking over is pretty small.
2. Second, native plants support native animals — there are tons of caterpillars and other insects that specialize on native plants. That means that they can’t eat non-natives, so landscaping with only non-native plants means that you’re essentially starving wildlife. The caterpillars supported by native plants turn into pollinators, and they’re also the primary food for baby birds, so native plants support bird populations too.
Planting a native tree (if you live in a place with trees) is probably the best single thing you can do to support wildlife.
What are three considerations to take before landscaping with non-native plants?
If you are planting non-natives, the main thing you can do is make sure that they’re not invasive. Probably the easiest way to do that is to google the plant name and “invasive” and try to avoid it if you see any information popping up about invasive tendencies.
Invasive plants aren’t necessarily invasive everywhere (they might only be harmful in part of their non-native range). But with big changes like climate change, it’s becoming harder to predict what could be invasive in a given ecosystem. Better to avoid planting invasives entirely.
What are three misconceptions about invasive plants?
Most people would probably think that we know which plants are invasive and stop them from being grown and sold. Unfortunately, that’s rarely true.
Few states have the resources to invest in preventing invasions, which means that state and federal regulations lag far behind current sales of non-native plants. We simply don’t have the resources or personnel to evaluate risk from thousands of species and move from risk assessments to prohibiting sales. Some states don’t have any laws to prevent the sale of invasive plants at all.
The result is that over 60% of known invasive plants are still offered for sale in the U.S. So just because you see a plant for sale doesn’t mean that it’s safe for the environment.
What are three invasive plants in the U.S. to watch out for?
Unfortunately, there are hundreds (maybe even thousands) of invasive plants in the U.S. Once you learn a few in your area, you’ll probably start noticing them everywhere.
What is one way people can help stop the spread of invasive plant species in their area?
Not planting them is by far the most important way to stop invasive plant spread. If you already have some invasive plants in your landscape (not uncommon), you can also work to slow their spread by cutting them back, smothering them, or using herbicides.
Most homeowners use way more herbicide than recommended though, so be careful about herbicides also affecting non-target native plants.
If you’re looking for advice on managing invasive species, you can probably find some from your local university extension office or from area NGOs that specialize in conservation.
What, if anything, can local or state governments do to reduce the impact of invasive plants?
- Being proactive about stopping invasive plants before they arrive is the most effective (both cost-effective and ecologically effective) way to manage invasions.
- Write to your representatives about enacting, funding, or strengthening regulations to prevent the ongoing sale of invasive plants.
Behind the ranking
First, we determined the factors (metrics) that are most relevant to rank the States With the Most Invasive Plant Species. We then assigned a weight to each factor based on its importance and grouped those factors into 3 categories: Invasive Plant Presence, Climate, and Regulatory Membership. The categories, factors, and their weights are listed in the table below.
For each of the 50 states and the District of Columbia, we then gathered data on each factor from the sources listed below the table.
Finally, we calculated scores (out of 100 points) for each state to determine its rank in each factor, each category, and overall. A state’s Overall Score is the average of its scores across all factors and categories. The highest Overall Score ranked “Most Invaded” (No. 1) and the lowest “Least Invaded” (No. 50).
Notes:
- The “Worst” among individual factors may not be No. 50 due to ties.
- “Number of Invasive Plant Species” includes terrestrial and aquatic plant species listed on the U.S. Department of Agriculture’s National Invasive Species Information Center site.
- “Number of Invasive Plant Species Reported” includes invasive and non-native plants mapped by a database of citizen scientists and managed by the University of Georgia Center for Invasive Species and Ecosystem Health. These may include non-native plants that have yet to be classified as invasive and may also include negative and eradicated records.
Sources
National Association of Invasive Plant Councils, National Invasive Species Information Center, National Oceanic and Atmospheric Administration, University of Georgia
Final thoughts: 5 invasive plants to watch out for
Research suggests that invasive species have cost North America an estimated $26 billion or more each year since 2010.
Invasive species — bugs, plants, and animals included — can contribute to issues like tree cover loss and hog resources from local species, leading to species endangerment and extinction. Meanwhile, planting native species can reduce water bills, preserve local biodiversity, and control erosion.
Click through our slideshow below to learn more about 5 invasive species that might be right in your backyard.
Chinese wisteria is a fragrant and fast-growing vine that can live for more than 50 years. While appealing to the eye with beautiful flowers, this invasive plant is known to cover and kill plants and trees.
Photo credit: Krzysztof Ziarnek, Kenraiz | Wikimedia Commons | CC BY-SA 4.0
Tree-of-Heaven is a large and smelly invasive tree that can survive and spread under harsh conditions. The tree produces chemicals with a herbicidal effect, killing neighboring native plants. It also attracts the invasive spotted lanternfly.
Photo credit: Cbaile19 | Wikimedia Commons | CC0 1.0
Frequently spotted alongside the road, Kudzu is a wide-spreading invasive vine. Growing up to a foot per day, it can smother forests, agricultural lands, and vacant lots. It is also known to disrupt the railroad and soybean industries.
Photo credit: Scott Ehardt | Wikimedia Commons | Public Domain
Commonly sold in plant shops, English ivy is a ground cover and vine bearing toxic leaves and fruit. Known to dominate understories and tree canopies, the vine blocks sunlight from reaching other vegetation, killing plants and preventing new growth.
Photo credit: Forest and Kim Starr | Flickr | CC BY 2.0
If you spot giant hogweed, stay away! This giant invasive herb can surpass 14 feet in height, and contact with its sap can cause severe burns, scarring, and sun sensitivity. This plant can produce between 20,000 and 100,000 seeds, which can survive in the ground for more than 5 years.
Photo credit: Andrew | Wikimedia Commons | CC BY 2.0
Avoid invasive plants and noxious weeds, and hire a local Lawn Love crew to fill your landscape with native plants.
Media resources
Quotes from Lawn Love Editor-in-Chief, Sharon Sullivan
- 19 states are members of the National Association of Exotic Pest Plant Councils, a coalition working to manage invasive plants spreading in natural areas nationwide.
- Luckily, California (No. 1) is a top state for animal lawn mowing — renting goats and sheep to cut grass and foliage. Targeted grazing by animal mowers can naturally help manage invasive species. Consider adopting or renting a goat for your natural land management projects.
- States like Pennsylvania (No. 17), Missouri (No. 18), and Maryland (No. 19) are taking legislative action to ban harmful species like Callery pear trees from being sold at local nurseries.
- Alaska (No. 51) has the fewest invasive plants to look out for — just 15 species according to NISIC. However, the state is experiencing a recent surge of non-native plants due to shifting wildfire patterns and climate change.
• High-resolution images of states
Main photo credit: U.S. Fish and Wildlife Service – Northeast Region | Flickr | Public Domain
