Japanese Stiltgrass

Photo: A Japanese stiltgrass investation at the Marie Butler Leven Preserve.

This post is the first of our Invasive Plant Profiles. Once a month or so, we’ll feature an invasive species that we are actively working to remove from our local parks. It might, though hopefully isn’t, one that you have in your backyard! We hope that you’ll find this series informative and fun.

Japanese Stiltgrass (Microstegium vimineum)

As you’ve undoubtedly seen in our newsletter, The Acorn, we’ve been hard at work all year removing a variety of invasive alien plants from the Marie Butler Leven Preserve, located in McLean, VA. This summer, we’ve dedicated many volunteer and staff hours to removing Japanese stiltgrass. A big thanks to our Restoration Site Leaders for leading additional volunteers events! This is an invasive that, up until a few years ago, wasn’t present in large quantities in the forests of the Preserve. Over the past few years, we’ve witnessed and attempted to halt its progression into the restored and unrestored forested areas of the Preserve.

In order to control Japanese stiltgrass, it is essential that you prevent the plants from setting seed. Stiltgrass is an annual grass, meaning each plant (roots and all!) dies off at the end of the season; if you’re able to stop new plants from growing, then you can suppress the infestation. Each plant can produce up to 1,000 seeds that can remain viable for at least 3 years. The seeds themselves are sticky (but not as sticky as wavyleaf basketgrass!); they easily cling to your shoes or the fur of your dog and then drop where you walk. We’ve heard park managers say that they can tell where people have walked off of trails, because patches of Japanese stiltgrass pop up where they’ve stepped. At Huntley Meadows Park, Resource Manager, Dave Lawlor has installed boot cleaning stations at trailheads to help stop the spread of Japanese stiltgrass seeds. Stiltgrass can quickly take over a disturbed site, but will also happily invade undisturbed sites, displacing native vegetation as it goes. Fortunately, like many annual grasses, stiltgrass has very shallow roots, making it very easy to pull. (You just have to be sure to pull every single one!)

We started hand-pulling stiltgrass stands in late June, before it began to set seed, collecting the offending plants into piles and leaving them to decompose. But now that it is fall, the plants have begun to produce seed and it is important that we bag the plants to prevent seed from entering the soil’s seed bank (the soil’s natural reserve of viable seeds).

Japanese stiltgrass can be easily identified by a few features. Its stalk forms stilt-like stems that stick up out of the soil; its pale green leaves have a distinctive silverish stripe down the center (unlike one of our native grasses, Leersia virginica, that looks similar); and, as I mentioned earlier, it has very shallow roots, making it unusually easy to pull out.

Apparently, stiltgrass was originally introduced to the United States around 1919 when it was used as a packing material to ship porcelain from China. Like many of our common invasives, it was originally introduced in one area of the United States (in this case it is believed to be Tennessee) by accident and has slowly been spreading ever since. One of the many problems with Japanese stiltgrass is that it thrives in many growing conditions. You can find it in full sun or full shade; along roadsides or deep in the forest; on the forest edge or in open meadows. At Marie Butler Leven Preserve, we have found stands just about everywhere: in the meadows, along the forest edge, and deep in the forest. Our strategy so far has been to carefully hand-pull plants from areas where they are threatening restored sections and then to work our way to unrestored sections.

As with most invasives removal, it will take a number of years to suppress stiltgrass at the Preserve, but with the help of our volunteers, we are confident that we’ll get there!

For more information check out the National Park Service’s Plant Invaders of Mid-Atlantic Natural Areas brochure or their advice on controlling grasses and sedges.