Who knew a grass could be so aggressive?! Japanese stilt grass, an invasive species from Asia, is just that and is making its way to the forest floors of Southern Indiana.
Japanese Stilt Grass
Japanese stilt grass first arrived in the United States as a result of its use as a packing material for porcelain. It has since spread to most of the states east of the Mississippi, appearing in southern Indiana in the early 1990's. Well-adapted to low light conditions, Japanese stilt grass seriously threatens our forest communities. Once introduced to an area, the grass will easily create a lawn in a forest understory. The species seems to always show up first on public natural lands at the trailhead - which makes sense since hikers' boots are mainly responsible for moving it around.
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Luckily Japanese stilt grass is one of the few grasses that are easily identifiable. By looking for a distinctive silvery stripe down the center of the upper leaf surface, you know you found it. Leaves are around 3 inches long, lance-shaped and a bit asymmetrical. It likes to sprawl and will grow slowly throughout the summer, reaching heights of 2 - 4 feet if enough light and water is available. Tiny flowers appear in late summer (from August to September) with fruits maturing soon after. By late fall the grass will die back, leaving dead orange-tinged plants.
Stilt grass reproduces exclusively by seed with individual plants producing 100 to 1,000 seeds that fall close to the parent plant. Seed may be carried further by water currents during heavy rains or moved in contaminated hay, soil and more often, on footwear. Japanese stilt grass seed remains viable in the soil for five or more years and, unfortunately, germinates readily.
Controlling Japanese Stilt Grass
Once introduced along roads, trails or other disturbed areas, the grass moves into the understory of forests. It spreads quickly, and will out-compete and displace native plants and tree seedlings. Abundant populations of white-tail deer may facilitate its invasion by feeding on native plant species and avoiding stilt grass.
There are a variety of ways to control Japanese stilt grass, but the best practice—as with any invasive species—is to prevent an invasion in the first place. If Japanese stilt grass is not yet in your area, keep it out by being sure to brush your boots after visiting forested areas in central or southern Indiana. Take care to not carry this invader into new areas on your boots.
Once it is established in an area, the species can be controlled in a couple ways:
Manual/Mechanical – For very small infestations, simply pull the plants out of the ground before they flower. For larger areas, weed-whack the plants to the ground in September, shortly before it produces seed but too late for it to regrow before the first frost. Since it is an annual, preventing the plants from setting seed is all you need to do to eliminate the species from an area. Of course, it will be necessary to pull or mow areas again each year until all the seeds are gone from the site.
Chemical – For extensive infestations, where mechanical methods are not practical, systemic herbicides such as glyphosate (tradename RoundUp, or Rodeo in wetland sites), or grass-specific herbicides like fluazifop-p-butyl (tradenames Fusilade or Fusion) are effective. Spraying areas with a very dilute solution of Fusion (1/2%) plus a surfactant has been very successful at killing stilt grass without impacting other species, even perennial grasses. Plants should be sprayed between June and August, when the plants are actively growing but before flowering. Spraying is generally more effective earlier in the summer and less effective during drought periods.
*Please follow instruction and use extreme caution when working with any herbicides.