Control of Japanese Stiltgrass

Question: I have 40 acres that is simply covered in stiltgrass! What can I do to get rid of this weed?

Thanks for your question! Japanese stiltgrass (Microstegium vimineum), a native to Asia, is an invasive grass to Virginia. Luckily, this grass is an annual and as such, doesn’t come back year after year. It can reseed itself, so the key to eradication is to prevent seed production. Control of Japanese stiltgrass can be a challenge since it can establish a persistent seedbank (particularly when you have 40 acres!). With hard work and persistence, Japanese stiltgrass can be controlled.

Let’s discuss what a “seedbank” is in your yard. A seedbank is all the viable seeds that exist in the soil of a given area. For Japanese stiltgrass, this means all the seeds that are viable and will reintroduce stiltgrass next year or even the year after that.

If you have a small property or have just a small amount of Japanese stiltgrass, the best approach is to prevent it from going to seed. Since it is an annual, it needs a seed to germinate and grow back next year. If you prevent seed production, you can control this grass. Mow the grass frequently on a low setting or pull the grass out by hand or by other mechanical means. If it is in an area that can’t be mowed, chop the grass down regularly by using a trimmer.

Controlling Japanese stiltgrass over a large area can be time-consuming and difficult. Plan on at least 5 to 7 years to get rid of it entirely. The first step, as stated above, is to mow frequently and pull as much as you can out by hand. This will need to be done for many years because of the seedbank. Another method to control the grass and, likely a better option for control in larger areas, is the use of an herbicide.

Glyphosate is a nonselective herbicide, meaning that it will kill or damage any plants around the grass that may accidentally be sprayed. There are other herbicides that can be used against Japanese stiltgrass. Be sure to read the label thoroughly and follow the directions exactly. Visit here for more details.

Consider planting an alternative groundcover in the place of the grass you remove. When you remove one plant from the landscape, another will grow in its place. It is important to fill this space with a plant better suited for your landscape. Visit here for native groundcover options.

Control of Japanese stiltgrass is a challenge, but can be achieved through consistency and vigilance. If you have successfully controlled this weed one year, you may want to consider the use of a pre-emergent herbicide in subsequent years. Applied 2 to 3 weeks before seed germination, it can prevent germination and reestablishment of stiltgrass. However, a pre-emergent herbicide will have little effect on plants that are already present.

More question on Japanese stiltgrass? Please feel free to contact the Piedmont Master Gardener’s Horticultural Help Desk. More information about this free service is located here.

References:

Invasive Plant Species Management – Japanese stiltgrass (Microstegium vimineum),” Penn State College of Agricultural Sciences.

Invasive Alien Plant Species of Virginia – Japanese stiltgrass (Microstegium vimineum),” Virginia Native Plant Society & Department of Conservation and Recreation.

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