Invasive species. Not a sexy topic, but an increasingly important one. Invasive species are often quite attractive, but they are strangling our ecosystems, deeply hurting their ability to support our native animals like songbirds and pollinators. Invasive plants are an important rpart of why our insect and bird populations are plummeting.
It turns out that native animals cannot really use non-native plants. Why? Because our native animals evolved in tandem with our native plants, animal bodies "learning" to neutralize specialized chemicals the plants produce or syncing the timing of their animal life cycles to fit that of "their" plants. This is particularly true for the young (a.k.a. caterpillars) of butterflies, moths, and skippers. And those same caterpillars are the primary source of protein that fuels the growth of baby birds.
Invasive plant species are non-native plants that really, really like it here and that are taking over entire ecosystems, displacing the native plants needed by our native animals.
While kudzu ("the vine that ate the south") is the poster child for invasive species, in this post I want to talk about a species that is less visually obvious but just as detrimental: Japanese Stiltgrass (Microstegium vimineum).
Frankly, I think that Japanese Stiltgrass is quite pretty, especially if it's getting enough water. So what's the problem?
The problem is that nothing eats Japanese Stiltgrass here in the United States, although presumably it is used by wildlife in its native East Asia. Unlike most grasses, this plant thrives in the shade - and it has taken over huge expanses of woodland understory in the eastern United States. Where Japanese Stiltgrass grows, it crowds out most other woodland understory plants, creating a pretty - but functionally useless - understory.
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| The forest floor here is carpeted with Japanese Stiltgrass - pretty, but useless to wildlife. August 16, 2025 |
In our woodlands, you might as well carpet your ground with synthetic carpet for all its wildlife value once stiltgrass takes hold.
Japanese Stiltgrass is an annual, so all of the plants you see growing this year will die when frost hits. Like most annuals, however, it is a PROLIFIC reseeder and its seeds remain capable of germinating for multiple years. If it seeds this year, you WILL have it next year.
So how to get rid of it, especially if you have a lot of it? It's best to use a couple of its growth characteristics against it: first, stiltgrass seeds late in the growing season and, second, it's shallow rooted. So....
1). It's EASY to pull out. I start pulling out stiltgrass as soon as I see it beginning to grow in late spring. My mantra is "a year of seed equals 7 years of week", which is great motivation! I pull it throughout the summer. After several years of careful diligence, I have relatively little left in our 2/3 acre yard.
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| Here, Japanese Stiltgrass (with broader leaves) is mixed in with sedge. August 16, 2025 |
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| A closeup of a sprig of Japanese Stiltgrass, showing its characteristic bright green color and the slightly off center silvery stripe found on many leaves. August 16, 2025 |
2). DO NOT mow it during the summer, as that will encourage it to set seed close to the ground. Wait until you start to see the flower/seed heads developing in late summer or early fall, then scalp the entire area, mowing as close to the ground as possible. (The seed heads look rather like crabgrass seed spikes.) If you do this - and time it well, the plant does not have time to regrow and set seed before being killed off as winter sets in and you've avoided a huge influx of new Japanese stiltgrass seed.
3). Some folks use a pre-emergent weed suppressant in the spring, but that will suppress ALL germinating seeds, not just stiltgrass seeds, so I don't choose to use this method.
NOTE: This is not a single year project. Like all invasive species, Japanese Stiltgrass is very good at spreading and colonizing. You will have leftover seeds in your soil's seed bank, plus new seeds will regularly come in from surrounding yards or "wild" areas on the feet of animals or on car/tractor tires or seemingly by "magic". If you are in an infested region, you will always have some stiltgrass trying to move in. However, you can get it under enough control that occasional hand pulling is more than sufficient to keep it out.
If you find Japanese Stiltgrass in your garden or yard, I highly encourage you to remove it and work to keep it out. If you don't, a little will quickly become a lot, as is the way with invasive plants - and the habitat value of your yard will decrease significantly. Best of luck!
