July 1, 2026: Thank you for visiting! Please note, this page is being built out over time. 

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Thank you for your interest in this important topic.  On this page, you'll find information about:

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• Definitions for native, non-native, and invasive plants

• Why some invasive plants spread so successfully

• The environmental impacts of invasive plants

• Resources to help you identify and manage invasive plants responsibly

Everyone can play a role in preventing invasive plant spread. Learning to identify invasive plants, choosing native or non-invasive alternatives for your landscape, and removing invasive species before they become established are simple but meaningful steps that help preserve New Hampshire's natural beauty for future generations.​

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Information below is adapted from articles provided by the USDA: National Invasive Species Information Center and Forest Service.

 

What Is an Invasive Species?

An invasive species is one that meets both of these criteria:
It is not native to the ecosystem where it is found.
It causes—or has the potential to cause—harm to the environment, the economy, or human health.
It's important to remember that not every non-native species is invasive.

Defining Native vs. Non-Native

A native plant naturally occurs in a particular region without human introduction.
A non-native (or introduced) species has been brought to an area, either intentionally or accidentally. Many non-native species provide benefits and coexist without causing problems.
For example:

• Tomatoes and peppers originated in South America but are valuable garden crops throughout North America.

• Lettuce was first cultivated in ancient Egypt.

Because of this, the terms "non-native" and "invasive" should not be used interchangeably.

Why Are Invasive Plants So Successful?

Invasive plants often have characteristics that give them a competitive advantage over native species. Some of these traits include:

• Producing large numbers of seeds, allowing them to spread quickly.

• Growing especially well in disturbed areas, such as roadsides, construction sites, and recently cleared land.

• Having seeds that travel long distances by wind, water, birds, wildlife, or even on people's clothing, equipment, and vehicles.

• Developing extensive root systems that spread aggressively and produce new plants far from the original one.

• Forming dense root networks that crowd out nearby vegetation by taking up available water, nutrients, and space.

• Releasing natural chemicals into the soil that can slow or prevent neighboring plants from growing, giving invasive species an additional advantage.

Many invasive plants are attractive ornamentals. For example, Dalmatian toadflax has bright yellow flowers that resemble snapdragons, making it appealing in gardens despite its ability to spread aggressively into natural areas.

How Do Invasive Plants Affect Our Environment?

Once established, invasive plants can have widespread effects on both natural ecosystems and human activities. Some of the most significant impacts include:
 

• Crowding out native plants by competing for sunlight, water, nutrients, and growing space.

• Reducing plant diversity, resulting in less resilient ecosystems.

• Degrading habitat for birds, pollinators, and other wildlife that depend on native vegetation.

• Contributing to the decline of many rare, threatened, and endangered species. Across the United States, invasive species have played a role in the decline of approximately 42% of federally listed threatened and endangered species and are the primary cause for about 18% of those declines.

• Lowering the productivity and quality of agricultural land.

• Affecting streams, lakes, and wetlands by reducing water quality.

• Increasing the risk of soil erosion as native plant communities are displaced.

• Limiting recreational opportunities such as hiking, fishing, hunting, and wildlife viewing when natural areas become overrun.

 

Source articles: 

https://www.fs.usda.gov/managing-land/invasive-species

https://www.invasivespeciesinfo.gov/what-are-invasive-species

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Important Reminders: 

 

When removing or managing invasive plants, your safety should always come first.

• Wear appropriate personal protective equipment (PPE). Gloves, long sleeves, long pants, and sturdy closed-toe shoes can help protect your skin from scratches, thorns, sap, ticks, and poison ivy that may be growing nearby.

• Protect your eyes. Safety glasses are recommended when cutting or pulling woody plants or working around branches that may snap back.

• Use tools safely. Pruning saws, loppers, and herbicide applicators should be used according to the manufacturer's instructions.

• Wash clothing and tools after use. Seeds and plant fragments can hitchhike on boots, gloves, clothing, and equipment, potentially spreading invasive species to new locations.

• Know the plant you're handling. Some invasive plants can cause skin irritation or allergic reactions, while others require specialized removal methods.

Respect Property Rights

• Never remove or treat plants on property you do not own without the owner's permission.

• Applying herbicides on someone else's property without authorization may violate state law and could result in legal liability.

• Even well-intentioned removal efforts can unintentionally damage desirable plants, wildlife habitat, or private property.

• If you notice invasive plants on public or private land, consider notifying the property owner or the appropriate land manager rather than taking action yourself.

• When in doubt, ask first. Working together with landowners is the best way to protect both our natural resources and our community relationships.

Together, these impacts disrupt the balance of healthy ecosystems, making it more difficult for native plants, wildlife, and people to thrive.