Annual jewgrass goes by a number of different names. It is commonly referred to as Japanese stiltgrass, but may also be called basketgrass, bamboograss, or by its scientific name of Microstegium vimineum. Whatever the preferred name in your region, annual jewgrass can be extremely problematic as it can take over areas of struggling turf, particularly in shady areas. Annual jewgrass can thrive in areas with as little as 5% sunlight and can be much more invasive and prolific than other problematic grasses such as crabgrass.
This broadleaf weed germinates in early spring, well before other invasive grassy weeds. Its leaves are generally shorter and broader than other types of turf weeds. Annual jewgrass generally grows upright and is freely branched with sprawling stems that take root at the nodes. Stems are stiff and can grow as tall as three feet if left to its own devices. Its leaf blades tend to be wider than other types of grasses, and it can be particularly noticeable in shady areas where annual jewgrass thrives. Leaves of mature plants can be slightly hairy in appearance on the topside and free of hairs and membranous on the underside. This grassy weed tends to have a shallow and fibrous root system, which can intermingle with desired growth and compete for resources and crowding out native plant life.
Annual jewgrass is an introduced exotic plant that originates in Asia. It is currently prevalent in the southeastern United States where it was first recognized in Kentucky in the early 1900s. As already mentioned, it thrives in shady, moist areas that include disturbed areas, woodlands, wetlands, upland forests, and sparse low-maintenance turf. In general, infestations begin in disturbed sites and once established can easily spread into undisturbed areas.
As a summer annual, annual jewgrass begins germinating in the form of seedlings in early spring. It grows throughout the summer and tolerates light frosts. In autumn, the grassy weed will flower. Flowers are spikelets that appear on a branched spike. Each branched spike may have 1-3 branches that may grow as large as 5 centimeters long. It can produce a large number of seeds, which can be as many as 50,000 seeds per square meter. Fortunately, seeds are only able to germinate within 3-5 years, making it a much shorter-lived annual weedy grass than other problematic turf weeds.
There are several measures of weed control when it comes to annual jewgrass. If caught early in its life cycle as seedlings, manually pulling plants can be an extremely effective means of control. For more established areas of infestation, control measures are generally multi-pronged approaches, and it may take several years to eradicate. Mowing annual jewgrass low, particularly prior to seeding, can help prevent seeds from dispersing. Additionally, there are some post-emergent weed control products that can be effective against this broadleaf weed. Selective herbicides that are designed for crabgrass can actually be more effective on annual jewgrass than on crabgrass. Non-selective herbicides may also be used, but it is important to note that these weed control products are sometimes capable of killing everything around it (non-selective). Spreading mulch over landscaping beds can help prevent annual jewgrass.