Invasive Species Case Study: Japanese Stiltgrass

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.

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.

Here, Japanese Stiltgrass (with broader leaves) is mixed in with sedge.
August 16, 2025

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!

Then and Now: A Living Explosion

"The yard is alive, with the sound of music!  With songs that've been sung for a million years...."  (My deepest apologies to Rodgers & Hammerstein for that abysmal rewording of their song.)

The yard IS alive, now, but when we moved in, it was quiet and boring.  Here's a summary of our journey so far....

THEN:    

    When we moved to southeast Virginia in fall 2019, our "new" yard challenged us. 

    The Prairie Boy was overwhelmed by the trees, 100+' giants that dwarfed the prairie trees he grew up with.  He likes to see the horizon, and you basically can't do that when you are surrounded by giant trees.  The yard was an enigma to him.

    The Druid was excited about having real, live, BIG trees in her everyday life again, having a true forest garden.  Her elementary school days had been spent in the eastern deciduous woodlands and she missed the ambiance and the ecosystem.

    However, the yard has ended up stymying both the Druid and the Prairie Boy.  These weren't just tall trees, these were TALL trees.  The neighbors told many tales of trees falling unexpectedly and hitting houses, so every time the wind blew, a sense of uncertainty swept in as well.

    There were remnants of prior landscaping in the yard, but they were truly remnants:  solo large shrubs, deer pruned and lonely, unsupported by companions and some seemingly placed almost at random.  In the spring, daffodils emerged and bloomed beautifully, but there were no flower beds, there was no lawn, and there was little discernible landscape design of any sort.

    Making matters even less promising, the vast majority of the huge shrubs were non-natives:  Chindo Viburnum, Camellias, Burford Hollies, Little Leaf Hollies, evergreen Azaleas, (small) Boxwoods, and a huge Rhododendron.  For native shrubs, there were a couple large Yaupon Hollies, planted way too close to the old greenhouse wall, and 3 Yellow Anise Shrubs.  Neither of these species are technically native to southeast Virginia, but at least they were "near natives".  There were no true native shrubs.

    As far as the "forest floor" was concerned, the yard had a lot of Japanese Stiltgrass and other non-native weeds, a few huge clumps of old fescue, a bit of Poison Ivy, and not much else besides the springtime daffodils and summer snowflakes.

    How in the world could we bring this space to life?  How could we create cohesion, and even beauty, in this struggling and rather awkward space?  In the spring of 2020, shown in the photo above, our newly acquired yard felt barren, despite the towering 100' tall trees that graced it.  We'd been feeding birds all winter, but there was precious little other wildlife to be found:  a skink or two, squirrels (of course), and honeybees from neighbors' hives, but almost no native insects.  That summer we had an Eastern Ratsnake show up one day, only to be found dead in the neighbor's driveway not long after.  A Leopard Frog made a brief appearance, as did a toad or two.  That was about it.

   I started pulling out the Japanese Stiltgrass the first summer, sitting directly on the ground, clearing out that invasive annual a few square feet at a time.  I'd researched stiltgrass and I'd learned that it didn't bloom and set seed until late summer or fall, but at that point it seeded prolifically;  I was determined to avoid new seed falling in as large an area as possible.  As I sat on the ground working, I got to know our yard "up close and personal".  

For example, in the photo above, you can see the bloom of a Naked-Flowered Tick-trefoil and a sedge, both of which are native, interspersed with the invasive non-native Japanese Stiltgrass, which has the broader leaves.  These particular native plants aren't showy, but the native insects need and use them. 

    I found a few really nice surprises:  several Striped Wintergreen plants (two are shown above), Southern Adder's Tongue, a few native tree and shrub seedlings, 2 stunted Mayapple leaves,  2 or 3 single Bloodroot leaves, and some nice Partridgeberry vines.   Mostly, though, I found a lot of non-natives, some of which were problematic and a few of which were outright invasive.

    Most disturbingly, I found almost no life in the leaf litter.  We'd left the leaves on the ground in the fall, so we did have leaf litter itself, but despite hours of sitting on the ground, all I saw that summer were a few little black crickets.

NOW: 

    It's been 4 years since that first daunting summer.  The Japanese stiltgrass still shows up a little, but it's easily pulled as I meander in the yard.  I've moved on to actively extracting Asiatic Hawkweed, fescue clumps, and Ground Ivy.  Ajuga is on my radar screen.  We've left the leaves every year and a healthy leaf litter has started to develop, feeding and protecting the soil, as well as providing habitat for a myriad of little animals.

 We've established a series of paths in the front yard, outlining them with branches from the tree trimming that has occurred.  We've left a large log and several small sections of logs,  forming an impromptu "jungle gym" for our grandsons in the front yard.  These have become favorite seats for me, as well.  In the back yard, we have a brush pile that the birds and the skinks find irresistible.

    For the most part over these intervening growing seasons, I've welcomed whatever native plants wanted to show up in the yard, relocating a few of them, but generally just observing and enjoying.  Because we have many seedlings sprouting, I can tell which plants are the birds' favorites, species like Spicebush, Wax Myrtle, and Black Cherry.  We've also planted a lot of native plants:  ferns, Columbine, Beautyberry, Viburnums, Goldenrod, Mayapples, and Bloodroot, just to name a few.

    We fight the deer...and the voles...and even, for a brief time last spring, a groundhog.  The deer have kept our newly planted plants undersized, but with judicious and regular use of deer repellants, we're finally seeing some growth.  Last spring the voles set us back on our heels for a while, but they haven't been as bad this year.

    Most excitingly, our yard has come alive with animal life.  These days I hear bird song all day long from a variety of species, including Brown Thrashers like the one shown above.   Fireflies twinkle at night.  

Butterflies flit through the air.  During the summer, I see Zebra Swallowtails and Eastern Tiger Swallowtails almost every day, but to get both in the same photo last summer felt like a real coup!  

In the leaf litter, there are now millipedes (like the one in the photo above), as well as snails and centipedes and roly-polies and firefly larvae and a gazillion ants and ...and ....and crickets, too, of course.  Moths have FINALLY appeared, especially the drab little leaf litter moths that are so incredibly important as food for many other animals.  

Solitary native bees, like this Georgia Mason Bee (Osmia georgica), visit our flowers and nest in the yard, as do a variety of solitary wasps who feed their young with paralyzed spiders or crickets or caterpillars or beetle larvae, depending on the species, helping to keep those populations in balance.

    So far this spring, we've had the parent birds of 10 different species bring their young to our feeders, including Carolina Wrens, Hairy Woodpeckers, and Brown Thrashers.  The photo above is of a father Downy Woodpecker feeding his daughter last spring.

    Pileated woodpeckers forage regularly on the stumps and the decomposing wood logs lining our paths.  

, 

    We have an untold number of Broad-headed Skinks in the yard, including this pair who had set themselves up in a prime location at the base of a dead tree.  Last summer, I also saw a Little Brown Skink, a species that lives entirely in the leaf litter.

    Butterfly numbers and species have increased, including this Common Buckeye (Junonia coenia) from last August, but greedily I would love to see even more.  I'm hoping that my increasing numbers of native flowers and host plants will bring them in - and help raise up new generations of lepidopterans.

    Most excitingly, this spring we've now seen TWO Eastern Ratsnakes, a big one and a little one.  Presumably they are why the voles are less of a problem this year!

    I still feel like the yard's design is far from optimal, but I'm continuing to work on it, aiming for beauty and cohesion as well as for increasingly healthy native plant and animal populations.

    

Ours may not be the most classically beautiful yard in the neighborhood, but it's rapidly becoming a most vibrant one, our own fascinating wildlife preserve.