There are a wide variety of non-native invasive plant species that have taken hold in Madison County. These plants cause harm to the environment, as well as potential harm to human, animal, and plant health in the preexisting environment. Some of these damages can be caused by overtaking beneficial native plants in the ecosystem, act as vectors for diseases and other invasive species, such as invasive insects, and are unhealthy or potentially toxic to native animals. In this series, we will discuss identification and control of these prevalent invasive plants.
Identifying Japanese Stiltgrass
Japanese stiltgrass (scientific name Microstegium vimineum) is known by many names, including nepalese browntop, japanese grass, asian stiltgrass, flexible sesagrass, bamboograss, and several more. This invasive grass is a warm-season annual that grows in a bright green color that can grow up to2 to 3 feet in height. The blades of this grass consist of long, thin leaves that grow in an alternating pattern up the stems. Each blade is flat and slightly hairy on the upper and lower surfaces, with a whitish colored midvein that is not centered in the leaf, and nodes separating different pieces of the stems. These jointed stems range in colors from light greens to reddish purples, and are often lifted off of the ground by exposed roots that appear almost like legs, giving this plant the common name “stiltgrass” it is often known by. The flowers of this grass emerge as small spikelets of seeds grouped together, usually appearing from August to September.
This invasive plant prefers growing in moist, partially shaded areas, but is easily adaptable and can grow in many different soil conditions and areas. A single Japanese stiltgrass plant can produce anywhere from 100 to 1,000 seeds. These massive amounts of seeds produced by this invasive plant can also remain viable for up to five years, meaning that they can pop up in different environments years after they were deposited there by whatever various methods moved them to that area.
How It Spreads
Japanese stiltgrass is a prolific spreader due to the massive amounts of seeds produced by each individual plant. These seeds spread in a variety of different ways, which include by attaching to the hides of wildlife, and the clothes and shoes of people moving through these infested areas, as well as being spread by fill-dirt moved from place to place, contaminated hay, and even flooded areas. This invasive plant is severe threat in natural areas, as it is adapted to grow in low light and spread seeds in a way that is functional for the understory of a forested environment, and is a major threat to native, beneficial species in shaded floodplain areas and in areas that are subject to treatments that may disturb the soil, such as tilling, mowing, or ditching. Despite this adaptation to partially shaded areas with moist, acidic to neutral soils, Japanese stiltgrass can take root in drier areas with full sunlight. After about 3 to 5 years of growth, this invasive species can create monocultures of itself where it chokes out any other diversity of plant life in the area where it is growing, whether it be a forest floor, a floodplain, or a pasture. This invasive plant also is undesirable to wildlife such as deer, which removes any grazing pressure on the plant and allows it to spread more quickly and overtake plants that are being consumed by plant-eating wildlife.
Controlling Japanese Stiltgrass
There are a few methods of control that can be used to help combat Japanese stiltgrass. If it is possible, try to prevent the establishment of this invasive plant in an area by removing them when first noticed, and closely monitoring the site to remove any resprouts as soon as possible. Some of the methods that can be used to control Japanese stiltgrass include mechanical removal as well as chemical treatment methods. Mechanical treatments can be effective depending on the size of the infestation and the time of year that the method is being implemented. These methods include mowing, hand pulling, hoeing, weed-eating, and flame weeding. Hand pulling and hoeing can be effective on small infestations of Japanese stiltgrass, as it is not a practical choice for large areas that are covered with this invasive plant, while continuous mowing can be a better choice for control in those larger infested areas, but is non-selective and can also harm beneficial plants in the area. Using tools such as a weed-eater can help mow more selectively, but it can also be a difficult and time consuming method when trying to manage land. Flame weeding, which is the use of intense heat to manage weeds, can also be a selective method of control for Japanese stiltgrass, but it is not a viable choice in dry areas or during fire-risk seasons. Whatever mechanical method is chosen, it is important to match your timing to the stage of growth for the invasive plant. If the chosen mechanical control method is applied too late, Japanese stiltgrass will have the chance to spread the large amount of seeds that comes from each individual plant, and will make it more difficult in the following year to manage. Due to this, it is important that mechanical methods such as hand pulling, hoeing, and flame weeding be used before the plant flowers and disposed of through methods like burning to prevent it from potentially coming back if roots remain viable. When mowing or weed-eating, Japanese stiltgrass will continue to grow after being mowed, and still risks producing flowers and seeds if it is allowed to grow for too long, so the infested site must be monitored and frequently mowed to prevent it from going to seed.
Chemical control methods can also be viable and effective options for controlling large infestations of Japanese stiltgrass. Herbicides known for controlling crabgrass, another warm-season annual, have been shown to be effective on controlling Japanese stiltgrass, but there are herbicides specifically labeled to control this invasive plant as both a pre-emergent, and a post-emergent. A pre-emergent herbicide is a type of herbicide that prevents plants from sprouting by blocking the seed’s ability to germinate in the soil. In a landscape setting, some of these pre-emergent herbicides contain the active ingredients dithiopyr, and indaziflam. In other areas, read the labels on these Japanese stiltgrass specific pre-emergents to see the areas where they are labeled for use. These pre-emergents must be applied before seeds germinate to be effective, which means that the pre-emergent herbicides will need to be applied in mid to late winter. When planning to use a post-emergent herbicide, or a herbicide made to be used once the plant has sprouted, this treatment should be applied at a similar time to the mechanical treatments, before Japanese stiltgrass begins to flower and produce seeds. Low doses of glyphosate have been shown to be effective in controlling Japanese stiltgrass through a foliar application. To use this foliar application method, create a solution of 0.25 to 0.5 percent glyphosate and 0.5 percent of a non-ionic surfactant in water, and spray the Japanese stiltgrass with this solution until it has been thoroughly wet. When using glyphosate, be sure to use a product that is still listed for the area being treated as well, such as landscape and turfgrass for a residential area, forest for forested areas, and aquatic for wetland spraying. Multiple applications may be necessary for full control of Japanese stiltgrass, as using a post-emergent chemical treatment will not remove the existing seed bank in the ground. Be sure to apply as needed until the existing seed bank has depleted, and the invasive plant will not return.
No matter which methods are chosen to treat this invasive plant, make sure to continue to monitor the area so any sprouts or regrowth can be swiftly dealt with to prevent another infestation from beginning.
If you have any other questions about identifying or controlling Japanese stiltgrass, please contact the Madison County Cooperative Extension Center at (828) 649-2411, or reach out to me directly at peyton_duckett@ncsu.edu.
Citations
Hooks, C. R., & Joseph, D. (2022, June 14). Flaming as a Weed Management Tool. University of Maryland Extension. Invasive Species Leaflet. (2010, March). NCDA&CS, Forest Service Division.
Neal, J., & Judge, C. A. (2013, February 18). Japanese Stiltgrass Identification and Management. NC State Extension Publications.
North Carolina State University. (n.d.). Microstegium vimineum. North Carolina Extension Gardener Plant Toolbox.
