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Attack of the Japanese Stiltgrass

Attack of the Japanese Stiltgrass

Attack of the Japanese Stiltgrass

By Dave Jobes, Ph.D.

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I wanted to share a very nice article (below) on a subject that has been causing a great deal of headache for us here in Maryland for the last few years, and that is the onslaught of Japanese Stiltgrass (Microstegium vimineum). Here is a link to a Rutgers University article that goes into great detail on stiltgrass, and I’ll also share my own experience with this incredibly invasive species.

In the last 3 years, we’ve seen explosive growth of stiltgrass in our parks, yards, and gardens. Unfortunately, the best way to get rid of it is by pulling, hoeing, and thatching. Thankfully, stiltgrass has two features that make it somewhat easy to control (1) it has a very shallow root system so even gentle pulling is enough to easily remove it from the soil and (2) it dies off relatively early in the fall (at least here in Maryland), so you can begin overseeding to try to outcompete the stiltgrass for next season. It does, however, leave behind a rather nasty seed bank that will cause the stiltgrass to pop right back up in the spring if you aren’t aggressive enough (read the Rutgers article for more on the seed bank).

This does present one problem though, if you have a significant amount of stiltgrass in your yard. Standard yard grasses (i.e., bluegrass, fescue, zoysia, etc.) have an interlocking root system, so excel at keeping your soil intact, thereby preventing soil erosion. However, in areas where stiltgrass has essentially taken over, you run the risk of serious soil erosion, since the stiltgrass tends to die off in the fall, just in time for the rainy season. That combination of rain and bare areas leads to erosion, with loss of the rich soil and nutrients that are often found in the top layer of soil. So, timing of the stiltgrass die off in the fall and overseeding of your grass of choice is critical. Using aggressive overseeding in the fall, we were able to reclaim >90% of our yard between last season and this season, but it requires lots of pulling and seeding on an ongoing basis.

One other point to consider. In our area, zoysia grass appears to be particularly resistant to stiltgrass invasion (also crabgrass invasion too), presumably because it grows so densely packed together and doesn’t allow the establishment of stiltgrass and other weeds. Therefore, if you have a serious stiltgrass problem you might consider replacing your grass with zoysia to deter stiltgrass growth. If you want to learn more about zoysia grass, here is a nice place to start.