Japanese Stiltgrass Control: Now is the time! with American Green



Japanese Stiltgrass (Microstegium vimineum) is an invasive annual grassy weed native to Asia, that has entrenched itself in the Virginia landscape. First discovered in Tennessee in 1919, Japanese Stiltgrass (JSG) was used as packing material for fragile items coming from China. The seeds ended up in trash dumps where they were able to spread. Now JSG grows throughout our woods, roadsides and lawns.


JSG prefers damp areas with semi to full shade but is able to grow in full sun if there is an adequate water supply. Often mistaken for a form of crabgrass in lawns, JSG has been a thorn in the side of many homeowners over the past few years. Irrigated lawns with semi-shade are especially susceptible to the spread of JSG and in as little as one year a lawn can be inundated by this invasive. Most often, JSG spreads to lawns from adjacent woods by wind, animals, water, people and machinery that carry attached seeds.


Although there are many types of weed controls for JSG. The two main categories are post-emergence (weed controls for after the plant has germinated and has started to grow), most have limited effect and may not even be practical for use in turf grass areas. Glyphosate, for example, is very effective in controlling JSG but is a non-selective herbicide which means it will not only kill the stiltgrass, but it will kill the rest of your lawn as well. The other category is pre-emergence (weed controls that prevent seeds from germinating and forming roots therefore stopping the weed before it starts). The most effective and practical way to control JSG in lawns is through the use of pre-emergent weed controls like the ones used for the prevention of crabgrass. Timing is key for effective control of JSG. In Virginia it is best to apply a pre-emergent in the late winter; February through early March.


While applying a pre-emergent to lawns for control over JSG, there are some important factors to consider. The first of which is fall seeding. If seeding was completed on a lawn the prior fall the new grass must first be inspected to know what stage of growth the new grass has achieved. Pre-emergent herbicides prevent the formation of roots and can even make young tender roots die off. If lawns were seeded in late fall and new grass has not grown enough to be mowed three or more times then the use of pre-emergence the following spring may kill the new seedlings and undo a costly lawn upgrade. Another consideration is spring seeding with desirable turf grasses. If a pre-emergent is applied to the lawn in February or March then grass seed will not be able to germinate and grow in the spring. Also, there are many regulations on the amount of pre-emergence that may be applied to a lawn in any given year so it is always best to completely read the entire label of any product to be applied to the lawn and closely follow that label. Or have a licensed and certified lawn professional apply the product for you.


Overall, the control and prevention of Japanese Stiltgrass in your lawn is best achieved through monitoring the lawn and surrounding environment, forming a proactive strategy a year in advance if JSG is in the area, correctly applying pre-emergent herbicides to prevent the invasive plant and if you need help, do not hesitate to call a professional. American Green has been creating strategies for customer’s lawns for the management and prevention of Japanese Stiltgrass for years. If you have questions or need help, please feel free to call us for a free evaluation, plan and quote. We look forward to hearing from you. Thank you for your time today. 540-406-1766