Weed Warriors

Volunteers spread mulch in a forest.
Volunteers help lay down Mulch at National Public Lands day.

NPS Photo.


The War on Weeds

As suburban sprawl spreads around Valley Forge National Historical Park, the park becomes increasingly important as a refuge for native plants and animals. The habitats in the park, including oak and poplar forests, meadows, wetlands, water, and forested floodplains, support over 1,000 different kinds of plants and 300 animal species.

Non-Native Plants

Approximately 1/3 of the plants in the park are non-native. A non-native plant is a species that has been introduced with human help, either intentionally or by accident, and was not previously found in the area. Not all non-native plants are invasive. In fact, when some non-native plants are introduced to new places, they cannot reproduce or spread readily without continued human help (for example, many ornamental plants).

Non-Native, Invasive Plants

Thirty of the around 300 non-native plants found at Valley Forge are also considered invasive or "weedy" species that can cause significant environmental or economic harm, and/or pose a threat to human health. Non-native, invasive plants are our target in the "war on weeds."

Two volunteers help plant a tree.
Two volunteers help plant a tree at National Public Lands Day.

NPS Photo.

Why We Fight

The spread of non-native, invasive species is one of the leading causes of ecosystem degradation and loss of biodiversity worldwide. These plants can tolerate a wide range of environmental conditions, such as temperature, shade, and moisture and they often possess traits that allow them to spread rapidly, such as prolific seed production and rapid growth rate. Additionally, the predators, parasites, and diseases that keep these species in check in their native lands are not present here.

Biological Pollution

The negative impacts that non-native, invasive plants have on native plants and animals is called biological pollution or biopollution. At Valley Forge invasive plants are considered a direct threat to natural resources because they:

  • Out-compete native plant species for light, space, nutrients, and water.

  • Interfere with natural ecosystem processes such as forest regeneration, erosion and deposition, and nutrient cycling.

  • Threaten native wildlife by reducing the availability and quality of food resources.

It is estimated that non-native, invasive plants spread into an area roughly the size of Delaware each year. At Valley Forge, all habitats are experiencing some level of degradation and loss of diversity due to the spread of these aggressive invaders.


What Can I Do?

You can volunteer as a park Weed Warrior and participate year-round in activities to remove various species of non-native, invasive plants. 'Weed' removal is accomplished using mechanical methods, including hand pulling and cut and cover, and may also involve the use of hand tools. These are great opportunities for both groups and individuals. Participants should come prepared to get down and dirty!

All ages are welcome and park staff will provide necessary training and equipment, including gloves and eye protection. Participants should wear long pants, a long sleeve shirt and closed toed shoes such as hiking boots.

Receive a Weed Warriors button the first time you participate, and earn a Weed Warriors t-shirt after you participate three times!

Two volunteers help install fencing.
Two young volunteers help install fencing.

NPS Photo.

How to Join

To join the Weed Warriors visit volunteer.gov, or email our Natural Resources staff.

Check the current volunteer opportunities at Valley Forge.

Last updated: April 20, 2023

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Contact Info

Mailing Address:

1400 North Outer Line Drive
King of Prussia, PA 19406


610 783-1000

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