Invasive plant
Japanese stiltgrass
Microstegium vimineum
Japanese stiltgrass identification: a silver stripe down the blade, shallow roots and late-summer seed heads. Learn how to stop it before it seeds.
Published Last reviewed
Japanese stiltgrass is an annual grass with a silver stripe down the middle of each blade. It spreads by seed, dies back each fall, and returns from a seedbank that can last five years or more. The first decision is whether you can stop this year’s seed, or whether you need a multi-year plan.
What does Japanese stiltgrass look like?
The fastest check is the leaf. Look for a bright green, lance-shaped blade 1 to 3 inches long with a patch of silver hairs down the center. The shiny midrib is slightly off-center, and the leaf feels smooth when you rub it in both directions. Most native grasses feel rough along the blade.
Then look at the base. Stiltgrass roots at the nodes, and the shallow roots send up short props that look like stilts. In late summer, each stem ends in a small one- to three-branched flower spike. After frost, the dead stems turn straw-colored and can stay standing through winter.
How to identify Japanese stiltgrass
The native look-alike to rule out is Virginia cutgrass. It is a perennial, and its flower spike is much larger, up to 10 inches long. It also has patches of dense white hair around each leaf base. Japanese stiltgrass has smooth leaves, a small branched spike and no dense hair rings.
Crabgrass is the other common mix-up. Both are annual grasses, but Japanese stiltgrass germinates earlier in spring and matures later in fall. The silver stripe and the stilted roots settle it.
Why Japanese stiltgrass spreads
A single plant can make 100 to 1,000 seeds. The seed is small, sticky and easy to move on shoes, clothes, tires, tools and animal fur. It also floats, so water moves it along ditches and streams. Penn State Extension notes that the seed can stay viable in the soil for up to five years, and University of Connecticut Extension says five years or more.
The plant is also a soil-disturbance specialist. Digging, tilling or pulling too early can open ground and bring more seed out of the seedbank. That is why the timing advice below is not just about the plant in front of you.
How to get rid of Japanese stiltgrass
| Your situation | First move | What to watch |
|---|---|---|
| A small patch, before seed heads form | Pull by hand, roots and all. | Bag plants that have flowered. Pulling is easiest because the roots are shallow. |
| A larger patch, before late August | Cut at ground level with a string trimmer, or mow in late summer. | Penn State Extension says string trimming is more effective than mowing because mowing can leave stem nodes. Either way, finish before seed set. |
| A lawn with a history of stiltgrass | Apply a preemergence product labeled for the site by mid-March, or spot-treat young plants with a labeled postemergence product. | University of Maryland Extension names prodiamine for preemergence and fenoxaprop for postemergence in lawns. Follow the label. |
| A wet area or stream bank | Stop and check the label before you buy anything. | Use only an aquatic-labeled product, and do not spray the water itself. |
Herbicide is not a reset button. Penn State Extension notes that postemergence products do not affect seed already in the soil. The seedbank is the reason this is a multi-year job.
When to treat Japanese stiltgrass
| Time of year | What the plant is doing | What to do |
|---|---|---|
| Late February to mid-March | Seed is still in the soil, waiting for soil temperature to rise. | Apply a preemergence product by mid-March, or two to three weeks before germination. |
| April and May | Seedlings are emerging. | Pull small patches. Postemergence treatment can begin in mid-May. |
| June and July | Plants are growing fast and starting to crowd other vegetation. | Pull or cut. Delay major mechanical work until June so an early pass does not trigger another flush of seed. |
| Late July and August | Flower spikes are forming, then seed is maturing. | Make the last cut or pull before seed set. Penn State Extension says to finish before the seed heads emerge in late August. |
| September and October | Seed is mature and the plant is dying back. | Do not spread cut material. Bag seed heads and plan next year’s preemergence timing. |
| Winter | Dead straw is standing, but the seed is in the soil. | Map the patch and order the spring plan. |
Is Japanese stiltgrass regulated in your state?
| State | Status | What it means for a homeowner |
|---|---|---|
| Pennsylvania | Noxious, Class B | It cannot be sold, transported, planted or propagated. Existing patches do not have to be removed, but control is encouraged. |
| New York | Prohibited | It cannot be sold, imported, purchased, transported, introduced or propagated. |
| Virginia | Not on the noxious weed list | The separate DCR invasive plant list is advisory only. |
| Ohio | On the invasive plant list | It cannot be sold, propagated, distributed, imported or intentionally spread. |
| Wisconsin | Prohibited | It cannot be transported, possessed, transferred or introduced without a permit, and control is required. |
A plant can be a serious invader and still be legal to sell. Check your state’s current list before you buy, move or plant anything. The Pennsylvania and New York pages have the state contacts.
What to do this week
- Check the leaf for the silver stripe and the base for stilted roots.
- Walk the patch and mark where the seed heads are. Those are the plants you cannot leave.
- If the patch is small, pull it now and bag anything in flower.
- If the patch is large, put the late-summer cut on the calendar before the seed heads open.
- If you use an herbicide, read the label first. The label is the law, and the label for your product is the only rate that applies.
For the wider seasonal plan, see when to treat invasive plants and how to get rid of invasive plants without chemicals. Debris and seed heads go in the trash, not the compost; the disposal guide explains the bag-and-solarize method. More profiles are listed under invasive plants, and image credits are on the image credits page.
Identification
Look for the combination of characters below. A single feature is rarely enough, especially when a native look-alike is present.
- Height and habit
- A summer annual grass that grows 1 to 3 feet tall and forms a dense, arching mat. It looks a little like young bamboo and can tolerate low mowing.
- Leaves
- Alternate, lance-shaped and 1 to 3 inches long. A patch of silver hairs runs down the center of the blade, the shiny midrib is off-center, and the leaves feel smooth when rubbed in both directions. There are no auricles at the leaf base.
- Stems and roots
- Stems can root at the nodes, and the shallow fibrous roots send up short props at the base, which is where the name "stiltgrass" comes from. Dead, straw-colored stems can stay standing through winter.
- Flowers and seed
- In late summer and early fall, each stem ends in a small, one- to three-branched flower spike. A single plant can produce 100 to 1,000 seeds, and the seed can stay viable in the soil for five years or more.
- Season
- Seeds germinate in late winter or early spring, the plant grows through summer, and it dies back in fall. Leaves often turn purple or pale yellow before frost.
Look-alikes
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Virginia cutgrass
Leersia virginica
A native perennial grass with a much larger flower spike, up to 10 inches long, and patches of dense white hair around each leaf base. Japanese stiltgrass has a small one- to three-branched spike and smooth leaves.
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Crabgrass
Digitaria species
Another annual grass, but Japanese stiltgrass germinates earlier in spring and matures later in fall. The silver stripe down the center of the stiltgrass blade is a useful check.
Range and status
Native range: Asia (China, India, Japan, Korea and Malaysia)
Regulatory status by state
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pennsylvania Noxious weed
Japanese stiltgrass is a Class B noxious weed on the Pennsylvania Department of Agriculture list. Class B means it is widely established and cannot feasibly be eradicated. Noxious weeds cannot be sold, transported, planted or otherwise propagated in the state.
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new-york Prohibited
Japanese stiltgrass is prohibited under 6 NYCRR Part 575. Prohibited plants cannot be sold, imported, purchased, transported, introduced or propagated in New York.
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virginia Not on the state noxious-weed list
Japanese stiltgrass is not on Virginia's noxious weed list in 2VAC5-317-20. The separate DCR invasive plant list is advisory only.
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ohio Prohibited
Japanese stiltgrass is on Ohio's invasive plant list under OAC 901:5-30-01, which bans selling, propagating, distributing, importing or intentionally spreading it. It is not on the separate prohibited noxious weed list, so the management duty for those weeds does not apply.
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wisconsin Prohibited
Wisconsin classifies Japanese stiltgrass as Prohibited under NR 40. Prohibited species cannot be transported, possessed, transferred or introduced without a permit, and control is required.
Why it matters
Japanese stiltgrass forms dense stands in forests, floodplains, roadsides and lawns, where it crowds out native plants and reduces wildlife habitat. Its tiny seed moves on shoes, tires, tools and water, and it can stay alive in the soil for five years or more. A patch that is pulled after seed has formed can still spread, so the timing of the work matters as much as the method.
Management
Stop seed before late summer
Timing: June through late August.
Penn State Extension says the goal is to prevent seed set and limit competition with desirable plants. Complete mechanical work before the seed heads emerge in late August. If you wait until the seed is ripe, you have missed the part that matters most.
Pull small patches
Timing: Late July to August, before flowering.
The roots are shallow, so small patches pull easily. University of Connecticut Extension prefers pulling after July but before flowering, because pulling earlier disturbs the soil and can wake more seed in the seedbank. Bag plants that have flowered.
Cut low, and time it before seed
Timing: Late summer, before seed set.
Penn State Extension says cutting at ground level with a string trimmer removes all stem tissue and is more effective than mowing, because mowing can leave stem nodes that regrow. University of Connecticut Extension says mowing in late summer, after flowering but before seed set, can still reduce seed production. Both agree on the deadline, which is before seed.
Use preemergence herbicide before germination
Timing: Late February to mid-March.
Penn State Extension names prodiamine and pendimethalin as selective preemergence options and says to apply them two to three weeks before expected germination, generally by mid-March. University of Maryland Extension gives early March as its local guide. These products affect germinating seed, not established plants. Follow the product label; the label is the law.
Treat emerged plants in spring and summer
Timing: Mid-May through August.
Penn State Extension names glyphosate, glufosinate and quizalofop as postemergence active ingredients. University of Maryland Extension names fenoxaprop for lawns. Glyphosate and glufosinate are non-selective, while quizalofop is grass-selective. Near water, use only an aquatic-labeled product. Follow the product label; the label is the law.
Plan for the seedbank
Seed remains viable in the soil for five years or more, so one season will not clear a site. Monitor the patch each spring and pull or treat new plants before they flower. Replant bare ground with native or non-invasive vegetation so the next seed that germinates has competition.
Sources
Facts on this page were checked against the sources below. Each link shows the date the source was accessed.
- Japanese Stiltgrass — USDA National Invasive Species Information Center Accessed November 3, 2026
- Japanese Stiltgrass in Home Landscapes — University of Maryland Extension Accessed November 3, 2026
- Invasive Plant Factsheet: Japanese Stiltgrass — University of Connecticut Integrated Pest Management Accessed November 3, 2026
- Japanese Stiltgrass — Penn State Extension Accessed November 3, 2026
- Microstegium vimineum (Trin.) A. Camus (Nepalese browntop) — USDA NRCS PLANTS Database Accessed November 3, 2026
- Controlled Plant & Noxious Weeds Lists — Pennsylvania Department of Agriculture Accessed November 3, 2026
- Invasive Species Regulations — New York State Department of Environmental Conservation Accessed November 3, 2026
- 2VAC5-317-20. Tier 1, Tier 2, and Tier 3 noxious weeds — Virginia Administrative Code Accessed November 3, 2026
- Invasive Plants — Ohio Department of Agriculture Accessed November 3, 2026
- Regulated Species — Wisconsin Department of Natural Resources Accessed November 3, 2026
Related pages
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Spring Invasive Plants Checklist: What to Look For in March, April, May and June
Spring invasive plants checklist: what to look for and act on each month from March through June, with links to species and removal guides.