Diagnose and fix
How to Get Rid of Japanese Stiltgrass in Virginia Lawns
By Patrick Klippen, Owner & CEOB.S. Landscape Horticulture · VDACS certified applicator #141054
Published Updated
Short answer
Japanese stiltgrass is an invasive annual grass that spreads entirely by seed, so the control that works is a pre-emergent in early spring, the same window as crabgrass. Look for a silvery stripe down the center of each pale, lance shaped leaf and wiry stems that pull up easily. Pulling it by hand fails because one plant drops a huge amount of seed that stays viable in the soil for years.
What is Japanese stiltgrass?
Japanese stiltgrass (Microstegium vimineum) is an invasive annual grass introduced to the United States in the early twentieth century and now widespread through the Mid-Atlantic. Northern Virginia sits in the thick of it, and homeowners here often spend two summers fighting what they assume is crabgrass.
How do you tell stiltgrass from crabgrass?
Look for a silvery stripe of reflective hairs down the middle of the leaf, because stiltgrass has it and crabgrass doesn't.
| Trait | Japanese stiltgrass | Crabgrass |
|---|---|---|
| Leaf | Short, thin and pale green, shaped like a lance | Wider, coarser and darker green |
| Midrib stripe | Silvery stripe of hairs | No stripe |
| Habit | Sprawling, wiry stems that root along the ground | Low rosette spreading from one crown |
| Where it grows | Shade, moist ground, tree lines, creek banks | Full sun, hot edges, driveways, sidewalks |
| When it germinates | Early spring, in the same window as crabgrass | Soil near 55°F, mid-March to early April |
| Roots | Shallow and weak, and it pulls up easily | Tougher and fibrous, and it resists pulling |
Where it shows up on Northern Virginia properties.
Stiltgrass shows up first where mowed lawn meets a tree line, a creek, or an unmowed field, which describes a huge share of property boundaries in western Prince William, Fauquier, and Loudoun counties. If your lawn backs to woods or pasture around Haymarket, Warrenton, or Aldie, assume that back edge is under pressure. Seed works inward from unmanaged ground, so the middle of the yard is the last place you notice it.
Deer avoid stiltgrass and browse the natives around it, and that same wood line margin is where tick pressure is highest.
Why pulling it by hand does not solve it.
Pulling it by hand doesn't solve the problem because stiltgrass comes out so easily that you think you're winning. A single plant drops a very large amount of seed that stays viable in the soil for years, so one missed season undoes the work. Pulling is worth it on a small patch you catch before seed sets in late summer, but it won't hold a wooded edge.
The good news is that it is an annual.
Every stiltgrass plant dies each winter, so a properly timed pre-emergent in early spring prevents the whole generation. The timing matches crabgrass prevention, so one well planned spring application handles both.
- Get pre-emergent down before soil at two inches holds near 55°F, usually mid-March to early April.
- Extend it all the way to the mowed edge, where the seed is.
- Split the application to cover the late spring germination flush.
- Spot treat what comes through in early summer, while plants are small.
- Repeat every year, since on a wooded or rural edge this is ongoing maintenance.
What to do about plants that get through.
Treat survivors post-emergent while they're young, because small stiltgrass is far easier to kill than a midsummer mat. We use a selective grassy weed herbicide labeled for tall fescue, so the stiltgrass dies and the lawn doesn't. A lawn on a rural or wooded edge will always need more attention along that boundary, and our lawn weed control program covers it each spring. Most single-family lawns run $60 to $90 a visit.
No. Stiltgrass is a shade tolerant invasive with a silvery midrib stripe, while crabgrass is coarse, loves the sun, and has no stripe. They germinate in about the same window, so one pre-emergent prevents both.
Not on its own. Mowing before seed set in late summer reduces seed drop, but stiltgrass flowers low enough to seed under the mower deck. Use mowing to limit seed and pre-emergent to control it.
Not if your lawn borders woods, a field, or a creek. Seed keeps washing in from unmanaged ground, and the seed bank in your soil takes several clean years to run down. The realistic goal is keeping it out of the lawn with annual spring prevention.
The conditions it likes are everywhere out here, including shade, moisture, and long boundaries between mowed and unmowed ground. Heavy deer browsing also removes competing native plants.
Related guides
Keep reading.
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Crabgrass Prevention in Northern Virginia
Why pre-emergent timing runs on soil temperature instead of the calendar, and the mistakes that waste it.
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The Northern Virginia Lawn Care Calendar
What to do to a Northern Virginia lawn in every month of the year, and why fall matters more than spring.
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Tall Fescue Lawn Care in Virginia
The grass most Northern Virginia lawns are made of, and the one yearly habit that keeps it from thinning.
