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Problematic Plant Monitoring at George Washington Carver National Monument

Bright green sumac filling a field in front of a row of trees
Smooth sumac (shown here) in the north unit of George Washington Carver National Monument prior to removal and restoration of the site.

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What Are Problematic Plants?

Sometimes plants grow in places where they don't naturally occur and some plants can cause damage to ecosystems and even harm people. Exotic plants are nonnative species that are typically introduced into an ecosystem by human actions, whether intentional or not. Invasive plants are exotic species that cause ecological or economic harm. Pest plants, which can be native species, interfere with specific management objectives and are sometimes called weeds. We refer to the collection of exotic, invasive, and pest plants as problematic plants.

Problematic Plant Management

National parks spend a lot of time trying to remove or control problematic plants to protect native plant and animal communities and visitors at parks. When a plant species is impairing park resources, managers are required to control the plant. They use five criteria to decide what other problematic plants they will control: the origin of the species, prudence of the action, feasibility of controlling the plant, the harm or impact that the plant causes, and the harm that removal of the plant could cause. Environmental assessments, the professional judgment of experts, and scientific research provide the information managers need to make these decisions. Parks also consult with regulating agencies and the public.

Map of the 114 problematic plant search units on the park; average search unit size is 1.9 acres.
Map of the areas where we searched for problematic plants at George Washington Carver National Monument. The average size of these individual search areas is 1.9 acres.

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Plant Surveys

Park managers need to know where problematic plants are to control them. The Heartland Inventory and Monitoring Network collects information on the cover (a measure of how much ground is covered by the plant), distribution, and location of problematic plants at George Washington Carver National Monument. We surveyed the park in 2006, 2013, 2016, and 2020. Managers can develop management actions and track the success of their control efforts using the information from our surveys. We use an early detection watch list and a park-established watch list to search for problematic plants. Early detection species are plants that have not been detected on the park before but have the potential to grow there. Plants on the park-established watch list have been found in the park during previous surveys.

Problematic Plants at the Park

Since 2006, we have identified 50 problematic plants at George Washington Carver National Monument; 35 of these species were found in 2020. Only tall fescue (Schedonorus arundinacea), one of the four species found at high frequencies, exceeded the 10-acre threshold we use as an indicator of whether a plant species will be easy or difficult to control. Because of the number, extent, and cover of problematic plants in the park and the small park size, control efforts should focus on treating high priority species across the entire park. High priority species may include plants capable of rapid spread, species that have low population levels, and species that can be effectively controlled.

Survey Highlights

  • The amount of smooth brome, poverty brome, cheatgrass, Japanese honeysuckle, and crown vetch in the park decreased.
  • Bald brome, bluegrass, and tall fescue were all widespread invasive cool season grasses in 2020, occupying more than 60% of the surveyed area.
  • The amount of Johnsongrass increased in 2020 to 37% of the areas searched.
  • Despite control efforts, the amount of sericea lespedeza remains relatively high. It was present in 62% of the search units.
  • Common woodland problematic plant species were eastern redcedar, osage orange, multiflora rose, Japanese honeysuckle, and wintercreeper.
  • Tree-of-heaven and Japanese barberry were found on the park for the first time in 2020.


A cluster of white and purple flower petals on a green stem with sparse compound leaves.
Dense stands of crown vetch threaten native plant communities. It spreads rapidly and is difficult to control. Treatment of this plant on the park appears to be helping reduce its populations.

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Species Spotlight: Crown Vetch

Crown vetch (Securigera varia) is a member of the pea family. It is native to the Mediterranean region of Europe, southwest Asia, and northern Africa. It was introduced to the U.S. in the 1950s for erosion control and is found in nearly all U.S. states. This plant aggressively invades natural plant communities, inhibiting native plant growth and creating too much shade for native plants to survive. It makes many seeds that remain viable in the soil for up to 15 years, and it can spread through creeping rhizomes, an underground stem that puts out lateral roots. These rhizomes can grow to 10 feet long causing rapid spread of the plant. Crown vetch is also difficult to control, often requiring many years of herbicide treatments, mowing, manual removal, and prescribed fire. A large patch of crown vetch in the northern prairie of George Washington Carver National Monument has been treated and is decreasing. We have not detected spread behond this patch. We monitor invasive plants to helps parks make decisions about managing and controlling them and to know if control efforts are working.

For More Information

Read the Full Report.

Check back later for updates. We will update this page each year as we gather information.

Visit the Heartland Inventory & Monitoring Network website.

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George Washington Carver National Monument

Last updated: June 22, 2022