How to Build Adaptive Invasive Plant Treatment Programs

Trying out alternative, scientifically grounded techniques could save time and money and yield benefits that go beyond individual park boundaries.

By Nicholas Stevenson

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About this article

This article was first published online on February 27, 2026, as part of the Picturing the Unseen series.

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An invasive plant management team member estimates the amount of invasive plants in a test plot.

NPS / Northeast Region IPMT

Invasive plants are plants from other places that spread and outcompete native vegetation. They can damage ecosystems, affect human health, and create economic costs. They’re widespread in U.S. national parks and so persistent that managing them can feel endless. Park biologists often spend much of their time reacting to non-native plant infestations. This can make it hard to monitor past treatments or explore innovative tools and techniques. The subsequent gap in knowledge about recent advances can lead to less effective management decisions. But there are scientifically grounded strategies to develop adaptive treatment programs that improve parks’ long-term outcomes.

Build In Monitoring

The key to effective park invasive plant management programs is to build in monitoring and research trials right from the start. This can ultimately save time and money, enhance program effectiveness, and boost staff engagement. The latter by fostering a sense of ownership and giving a deeper understanding of the work.

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It’s a far cry from gathering information solely through GPS points and hand-written pesticide logs.

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Incorporating monitoring can be done efficiently using tools like ArcGIS Field Maps or Survey123. These applications can automatically map the user’s position and allow them to input information directly on a phone or tablet. This ensures all the required data are collected, including georeferenced photo points that show changes over time. This results in a cheaper, safer, and more efficient workflow.

The National Park Service’s regional invasive plant management teams and many parks have adopted these tools. They’re also using the National Invasive Species Information Management System (NISIMS). The NISIMS data management tool allows for consistent and standardized data collection. It’s a far cry from gathering information solely through GPS points and hand-written pesticide logs.

A team member sprays common reed (scientific name: Phragmites australis) while another records GPS locations, percent cover, and herbicide use data.

NPS / Northeast Region IPMT

Give Wings to Park Data

Sometimes practitioners can only visit monitoring sites once a year. Understanding how successful a treatment is can help parks strategize the kind of work to be done, which techniques to use, and how many employees they will need for the following year. Practitioners consider a treatment successful if it eradicates at least 90 percent of the invasive plant. If results fall below this threshold, the park might need to make operational changes.

Effective management of invasive plants thus relies on recording results both immediately after treatments and for years afterward. At a minimum, monitoring records should show the actions taken, the dates of treatment, and the results (for example, the percentage of plants killed). Notes may also include unusual findings and recommendations for future action.

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Parks can adapt the guidance to their needs rather than create a new method from scratch.

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The National Park Service Inventory & Monitoring Division’s long-term monitoring protocols and resulting findings describe plot sampling techniques and how to track a wide range of variables. They can give park programs—regardless of scope—helpful insight and ideas. No matter the program goals, park staff may benefit by starting with one of the many existing protocols. Some of these are outlined in the division’s report, Guidance for Designing an Integrated Monitoring Program. Parks can adapt the guidance to their needs rather than create a new method from scratch. This saves time. It also ensures the data are compatible with broader monitoring throughout the national park system, increasing the data’s scientific utility.

Learn on the Fly

Japanese knotweed is a notoriously resilient invasive species. Over a two-year period, I tested several herbicides and application rates on this plant in the Delaware Water Gap National Recreation Area. The infestation followed a linear pattern along a trail and conveniently grew in separate, similarly sized blocks. These were ideal conditions for comparison studies. Internal trials showed that I could achieve over a 95 percent control rate while using 50 percent less herbicide. This improved safety for both staff and park visitors.

Japanese knotweed (Reynoutria japonica) has hollow, bamboo-like stems, broad green leaves and greenish white flowers in slender clusters. It grows up to 10 feet tall and can can take over large areas. A native of Asia, it was introduced to North America in the late 1800s as an ornamental plant.

NPS / Northeast Region IPMT

Incorporating simple experiments into routine treatments in this way helps build knowledge. Field staff can vary herbicide rates or test new active ingredients to determine what works best under specific conditions. Everyday work thus becomes a means to learn and improve.

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The total added effort amounted to just 5–10 percent of the project time.

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Just like monitoring, building trials and research into a treatment program can be as simple or as complex as time and resources allow. These experiments don’t require hours of advanced planning or a statistically significant number of replicates to be effective. They can be as straightforward as applying slightly different treatments to separate patches of invasive plants and using this to guide future work. Any information on improving efficiency is better than none. The more park staff examine their work, the more possible improvements will become apparent.

The trials I did at Delaware Water Gap required little additional time in the field. The total added effort amounted to just 5–10 percent of the project time. And that included thorough mapping, consistent documentation, and standardized monitoring. The insights gained will help improve management decisions for years to come. But even more kinds of useful experiments can be built into an invasive species treatment program.

A team member scans a wetland restoration area for tall emerging invasive plants such as common reed and Japanese knotweed.

NPS / Northeast Region IPMT

Go Beyond Conventional Techniques

There are benefits to going beyond conventional methods like spraying leaves, treating cut surfaces, or pulling out plants by hand. Other techniques may be more effective or more benign to staff and the environment.

Spraying dormant stems

In this technique, a mixture of herbicide, oil, and water is applied to resting invasive plants in winter, outside of their growing season. The plants absorb the mixture. This method is effective against dense stands of invasive shrubs and vines.

Injecting herbicide directly into plants (precision injection)

Precision injection can reduce environmental exposure and remain effective for months or years. It’s ideal for plants in sensitive habitats or in areas that visitors use.

Applying herbicide to lower part of stem or trunk (basal bark application)

Used in a mix with oil, basal bark application is a good option for large shrubs or trees. And it’s easier and safer than cutting them down with chainsaws.

Using the sun’s heat to kill weeds (solarization)

Solarization can be an option for small patches of invasive plants where herbicide use is restricted. The site is covered with a heavy tarp. This slows plant growth by essentially “cooking” the plants and seeds underneath.

Seeding a cover mix after spray treatments

Herbicide treatments are often followed by a carpet of new invasive seedlings that take advantage of the disturbance. Planting a fast-growing native species reduces this occurrence, making follow-up treatments easier and speeding site recovery.

NPS / Northeast Region IPMT

Up the Gear Game

Practitioners often rely on the same equipment, such as a backpack sprayer with an adjustable cone nozzle. This was true for me early in my career, when we used the same high-volume cone nozzle for every application. After switching to a narrow-angle (80 degrees) flat fan nozzle, treatments of low-growing invasive plants like garlic mustard (Alliaria petiolata) and knapweed (Centaurea spp.) became faster. The treatments also required less chemical, and we achieved better coverage and control.

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This was true for me early in my career, when we used the same high-volume cone nozzle for every application.

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By exploring other types of gear, practitioners can apply more efficient treatments. For example, certain sprayers can apply products in formulations other than liquid solutions, such as powders or dusts. Different kinds of nozzle tips can provide better coverage with less chemical when treating smaller plants. Specialized tools for cutting can make tree or shrub treatments easier and more effective. Different ways of planting native species may be better suited to specific habitats or seasons. These are just a few examples, and invasive plant management technologies are continually evolving.

Test it Out

The Species Strategy Library, available only to Department of the Interior staff, is a good resource for species-specific treatment prescriptions. A highly regarded public site is the Center for Invasive Species and Ecosystem Health. Practitioners will find these resources particularly useful when dealing with unfamiliar invasive plants.

Collecting basic data, like date, type of chemical mix used, plant species treated, and percentage of plants killed can reveal needed changes. In this case, the fewer killed plants in 2025 could be due to the chemical mixture used or environmental factors. To determine which, the team could try a different mixture under the same environmental conditions and time of year. The goal is to use as little chemical as possible but still get good results.

NPS / M. Lawrence. Data from Northeast Region IPMT.

But even when advice comes from experts or highly regarded websites or organizations, it’s often best to test it out. This is because things like recommended temperature ranges for herbicide application may not apply to a park’s local environment or a specific product. The shelf life of herbicides may vary under different formulations or conditions. The effectiveness of manual control methods depends on the species of plant and how large or abundant it is. And applying treatments at the optimal time may not be possible due to workload and staff limitations. When controlling invasive species, all results are local.

Realize It's Not the Last Word

Removing invasive plants isn’t the last word when restoring a site. It’s also important to identify the most effective native species, timing, and techniques for replanting. This is because a healthy native plant community can reduce the likelihood of invasives returning. Small-scale trials of different native plants or seed mixes can help future restoration projects succeed.

A simple garlic mustard (Alliaria petiolata) seed germination trial using an LED grow light, plastic pots, and a sterile soil mix. This experiment is to test if herbicide-treated plants can still produce viable seeds.

NPS / Northeast Region IPMT

If trials aren’t feasible, parks should try to get native plants from as local a source as possible. And they should use a less invaded site as a reference for potential species mixes. Regional sources, such as a state extension office or botanist, can recommend local native plant nurseries. But replanting native plants is almost never the end of the project. Monitoring, spot treating invasives, and planting natives in additional rounds will likely be necessary.

Work Smart

Adapting invasive plant treatments to evolving science, technology, and local conditions can help protect park visitors, staff, and resources. And the knowledge and skills gained enable parks to share their expertise within and beyond the National Park Service. For help in adapting their local programs, I encourage park practitioners to reach out to their regional Invasive Plant Management Team. These teams can provide guidance, on-the-ground resources, and collaboration opportunities to strengthen park programs. Many parks operate with limited resources. Working smart by using adaptive techniques to improve the effectiveness of invasive plant treatments is a no-brainer.

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Acknowledgments

Thanks to the staff (past and present) of the Northeast Invasive Plant Management Team for their opinions on this article and for helping on research projects in the field, and to our partner parks for providing the place and opportunity to improve our craft.

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About the author

Nicholas Stevenson is a natural resource specialist with the National Park Service's Northeast Region Invasive Plant Management Team. Photo credit: NPS / N. Stevenson

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Republishing this article

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Cite this article

Stevenson, Nicholas. 2026. “How to Build Adaptive Invasive Plant Treatment Programs.” National Park Service, February 27, 2026. https://www.nps.gov/articles/000/psv40n1_how-to-build-adaptive-invasive-plant-treatment-programs.htm