Problematic Plant Monitoring at Arkansas Post National Memorial

Controlling Chinese privet (shown here) is a priority at Arkansas Post National Memorial.

NPS

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 areas where we searched for problematic plants in the Memorial Unit and the Osotouy Unit at Arkansas Post National Memorial. The average size of these individual search areas is 2.0 acres.

NPS

Plant Surveys

Park managers have 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 Arkansas Post National Memorial. We surveyed the park in 2006, 2011, 2015, and 2019. 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 28 problematic plants at Arkansas Post National Memorial; 23 of these species were found in 2019. Our Heartland Invasive Plant Management Team focused control efforts on four species in the Memorial Unit: Chinese privet, hardy orange, black locust, and Japanese stiltgrass. We also controlled Chinaberry tree as we came across it while treating and removing the other species. We will continue to survey for and control these plants to protect the native plants and animals in the park.

Survey Highlights

• The amount of Chinese privet decreased from 7.8 acres in 2006 to 0.3 acres in 2019 but was found in half of the search units.
• Hardy orange decreased from about 82.7 acres in 2006 to 1 acre in 2019 and was growing in a third of the search units.
• Black locust was only present on a few of the search units in 2019 and has occupied an acre or less over the years.
• Despite control efforts, the amount of Japanese stiltgrass was similar over time. There was a decrease in 2019 but this may be due to flooding events. This grass spreads rapidly and can outcompete native species.
• Chinaberry tree decreased over time at the park.

Problematic Plant Species at Arkansas Post National Memorial (2006–2019)

Problematic plants found at Arkansas Post National Memorial (2006–2019). An asterisk (*) indicates that the species was not found during 2019 surveys.

Common Name	Scientific Name
silktree	Albizia julibrissin
alligatorweed	Alternanthera philoxeroides
giant reed*	Arundo donax
eastern baccharis	Baccharis halimifolia
bald brome, spiked brome	Bromus racemosus
Bermudagrass	Cynodon dactylon
Queen Anne's lace	Daucus carota
barnyardgrass*	Echinochloa crus-galli
common water hyacinth	Eichhornia crassipes
sericea lespedeza	Lespedeza cuneata
Chinese privet	Ligustrum sinense
Japanese honeysuckle	Lonicera japonica
Chinaberrytree	Melia azedarach
Japanese stiltgrass, Nepalese browntop	Microstegium vimineum
wartremoving herb*	Murdannia keisak
parrot feather watermilfoil*	Myriophyllum aquaticum
Kentucky bluegrass	Poa pratensis
hardy orange, trifoliate orange	Poncirus trifoliata
black locust	Robinia pseudoacacia
multiflora rose	Rosa multiflora
curly dock	Rumex crispus
Johnsongrass	Sorghum halepense
erect hedgeparsley	Torilis japonica
hedgeparsley	Torillis spp.
narrowleaf cattail	Typha angustifolia
common mullein*	Verbascum thapsus
bigleaf periwinkle	Vinca major
Chinese wisteria	Wisteria sinensis

Hardy orange grows very fast and can shade out native plants. When it is well established, it can form impenetrable hedges. This tree blooms in the spring and produces fruits in the fall and its wood is hard and dense.

M. Marquez

Species Spotlight: Hardy Orange

Hardy orange (Poncirus trifoliata) is in the same family as other citrus trees (Rutaceae), but it's fruits are extremely bitter. This shrubby tree has many long, sturdy thorns that can pop tires. A native of China, hardy orange was grown in Europe and brought to North America during colonial times. Colonists candied the rinds, made marmalade from the fruit, and used the fruit pectins to make jams and jellies. In China, this tree has been cultivated for thousands of years. Unfortunately, it is very invasive. It spreads aggressively and outcompetes native plants in woodlands, forest edges, and disturbed areas. Our efforts have decreased the amount of hardy orange at Arkansas Post National Memorial, though we are still finding it on about a third of the areas we monitor.

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.