Japanese stiltgrass was not on my radar until a recent visit to a local park. It had piqued my interest because of the lushness of the plants beneath a full canopy of trees. My first thought was, what is this grass that could be a recommendation for shady sights? My excitement quickly waned because our hosts explained that the annual grass unfortunately, is considered an invasive species. In fact, this non-native species from Asia, which was first found in Tennessee in 1919, can produce up to a 1000 seeds per plant and crowds out native plants. The seeds from this plant are dispersed by a number of mechanisms including foot traffic, water movement, equipment, and wildlife.
Japanese stiltgrass (Microstegium vimineum) can be found in disturbed areas such as; edges of fields, forests, ditches, recreational trails, etc. It grows in low-light environments with sufficient soil nutrients and moisture but it can also adapt to low-nutrient and low-moisture areas with adequate light.
Japanese stiltgrass leaves are flat, pale green, asymmetrically lance-shaped, and about 1–3 inches in length. Leaves are sparsely hairy on both sides and along the margins. A shiny, off-center, mid-rib is conspicuous on the upper surface, which is sometimes described as a silver stripe, and is a distinctive identification feature. Leaves are arranged alternately along the branched stem and project outward. Spikelike flowers up to 3 inches long develop in late summer or early fall in the axils of the leaves at the tip of the stem. A shallow and fibrous root system is a distinguishing characteristic that sets it apart from the native white grass (Leersia virginica), which has a stout rhizome.
Managing for Japanese stiltgrass is not unlike managing for other invasive plant species. It requires diligent, hard work! Inspection of equipment such as mowers, road maintenance equipment, and timber harvesting is important. Cleaning and sanitizing equipment with known stiltgrass infestations helps to prevent spreading of this grass. Hand-pulling is effective late in the season before plants flower. Pulled plants should be bagged. Mowing and/or weed eating is also effective if done before the plants mature and go to seed. Chemical control with non-selective herbicides, non-selective pre-emergent herbicides and selective grass-specific herbicides can be effective but may require more than one application over the course of a few years. When using any chemical always read and follow label instructions.