Invasive Plant Management

Invasive plants are a large and growing problem for many national parks. These unwelcome invaders reduce native biodiversity, alter forest structure, suppress tree regeneration, and pose significant threats to the long-term condition of parks’ forest health. Discover what Harpers Ferry National Historical Park, the National Capital Area, and the National Park Service are doing to address this issue.

 

 

An Invasive Plant Management Team member works to clear an area of invasive autumn olive.

NPS/W. Heideman

What are those people with the backpacks doing?

The National Park Service (NPS) employees with the backpacks are part of the park’s invasive plant management efforts. They are assisting with habitat improvement projects by managing invasive plants that are outcompeting native vegetation. The spread of invasive species is a major factor contributing to undesirable landscape level change and ecosystem instability in national parks.

Who does invasive plant management within the park?

NPS staff, contractors, and trained volunteers all assist with invasive plant management in national parks.

What are invasive plants?

Invasive plants are aggressive non-native plants that cause harm to the environment, economy, or human, animal, or plant health.

What’s the difference between native, non-native, and invasive plants?

Native plants are species that have occurred, now occur, or may occur as a result of natural processes. Each ecosystem has its own unique set of native plant species.
Non-native plants occur in areas where they didn’t originate. Some were intentionally introduced by humans, and others were introduced accidentally. They may or may not cause harm to the environment, economy, or human, animal, or plant health. Example: dandelion.
Invasive plants have a specific definition: non-native species that cause harm to the environment, economy, or human, animal, or plant health. Example: kudzu.
Learn more about invasive and non-native species.

 

Left image
The area pre-treatment.
Credit: NPS/N. Keefner

Right image
The area post-treatment.
Credit: NPS/N. Keefner

A 2017 wetland restoration action plan identified the area in these photos to have high restoration potential. Harpers Ferry National Historical Park staff are planning and coordinating the steps needed to manage this area as a scrub-shrub wetland with more native plant species. The National Capital Area’s Invasive Plant Management Team (IPMT) plays an integral role in the park’s plans. In October 2021, four IPMT workers (pictured) cut large, invasive autumn olive (Elaeagnus umbellata) at the site to make way for native plants.

 

 

Tree-of-heaven (Ailanthus altissima), one of the invasive plants treated by the park.

NPS Photo

Why does the park use herbicides?

The NPS uses the Integrated Pest Management (IPM) framework to determine the most effective treatment option for all pests, native and non-native. Herbicides are just one of many tools available for vegetation management. In many cases, herbicides can help land managers reduce the overall time commitment required to manage non-native invasive plants and allow park staff to manage a larger area. Herbicides are also a great tool for areas where ground disturbance is not feasible (for example, tree of heaven growing on historic earthworks). Finally, they may be the most effective treatment option for a particular species.

What plants are you spraying? Why those plants?

The NPS uses herbicides as one method to manage invasive plants. These plants can outcompete native vegetation, negatively change the landscape, and create instability within park ecosystems. Harpers Ferry NHP treats jetbead (Rhodotypos scandens), wavyleaf basketgrass (Oplismenus undulatifolius), and tree-of-heaven (Ailanthus altissima), to name a few.

 

Pesticide application signs label areas with active herbicide application.

NPS Photo

What chemicals are you spraying? Why those chemicals?

Products used by the park are registered for use with the state. They are also approved for use by our regional Integrated Pest Management (IPM) coordinator, who has reviewed each product, proposed treatment area, and target species in detail prior to any applications. All products used by the NPS are applied according to the directions listed on the label and are applied by trained Registered Pesticide Technicians and Applicators, or trained staff under the close supervision of Registered Pesticide Technicians and Applicators. Herbicide products selected by the park have been shown to be an effective treatment option for non-native plants targeted by the team.

Are the chemicals safe?

Herbicide products selected by the park have relatively low toxicity to fish, birds, and mammals. Areas treated with herbicides are safe to enter once the product has dried or if proper personal protective equipment (PPE) is worn: closed-toe shoes, socks, and long pants.

Why are the plants blue?

The blue color in the solution is dye that will degrade with exposure to sunlight. It helps the team see the areas that they have treated.

What if my dog has blue paws? What if I got blue on my clothes/skin?

If the dye gets onto your skin, clothing, or animal fur, it can be washed out with soap.

What if my dog ate some of the blue grass?

Visitors and their pets should remain on trails in areas with active herbicide application. Acute exposure through ingestion to mixed solutions used by the park program will most likely cause no harm to visitors or pets, but visitors can always contact the manufacturer on the number listed on the label. Areas with active herbicide application are labeled with Pesticide Application signs. On the back, you will find a name of the product that was applied at this location, the date of application, and contact information for park staff.

 

Learn more about Invasive Plant Management Teams:

• Invasive Plant Management Teams - Biological Resources Division (U.S. National Park Service) (nps.gov)
• Northeast - Invasive & Non-Native Species (U.S. National Park Service) (nps.gov)