Stiltgrass (Microstegium vimineum)

A carpet of stiltgrass plants on a forest floor  Chris Evans, University of Illinois, Bugwood.org.

 
 

Stiltgrass is an annual grass that grows well in forests. When plants die at the end of each year, it creates a lot of flammable material that can increase the likelihood of fires. Stiltgrass is a high priority for early detection in Minnesota.

Description

Appearance

Stiltgrass is an annual grass that can grow in thick carpets. It can grow up to 3 feet tall. Its leaves have a distinctive line of silvery/white hairs.

Leaves and stem

Leaves are 1-3 inches long and attach to the stem one at a time in an alternating pattern on the stem. Leaves taper at both ends and have a distinctive line of silvery/white hairs. This line is generally slightly off-center as opposed to directly down the middle of the leaf. Stems can reach up to 3 feet tall.

Flowers

The spikes of flowers can be 1-3 inches long with multiple small flowers along the spike (each flower up to ¼ of an inch long). Plants generally flower from late summer to early fall.

Seeds

Seeds are small (up to 1/8 of an inch long). Some stiltgrass seeds have an awn (small bristle) while others do not. A plant can produce up to 1,000 seeds.

Roots

Stiltgrass roots are fibrous and do not extend deep into the ground. There are roots that extend from nodes on the lower part of the stem, these are called “adventitious roots” and are what give stiltgrass the “stilts” that it is named for. Stiltgrass also has “stolons” (runners) which are above-ground stems that are horizontal and on the surface of the soil. As these stolons send out roots, new vertical stems can form. This allows the plants to spread, root, and create more vertical stems. If you pull up a stiltgrass plant, you may find that it is connected to other stiltgrass plants.

Biology

Stiltgrass is an annual grass that can grow well in shady areas. It does well in wet areas, forests, and along waterways. It can also be found in lawns and gardens. Its seeds spread easily along waterways. Stiltgrass produces some flowers that self-pollinate and other flowers that are wind pollinated. A single plant can produce up to 1,000 seeds in a year. Plants generally flower from late summer to early fall with seeds maturing from late September through early November.

Origin and spread

Stiltgrass is native to Asia and was first documented in the United States in 1919 in Tennessee, likely arriving due to use as packing material. It is present in much of the eastern United States but there are few reports in states near Minnesota.

Refer to EDDMapS Distribution Maps for current distribution.

Don’t be fooled by these look-alikes

  • Whitegrass, Leersia virginica (native) – Whitegrass is a perennial species so it has a more well developed root system than stiltgrass. Whitegrass leaves do not have the white stripe on the leaves that stiltgrass leaves have. See pages 30 and 31 in the Delaware Department of Agriculture’s Mistaken Identity guide for a detailed comparison of the two species.
  • Smartweeds such as lady’s-thumb, Persicaria maculosa (non-native) and Pennsylvania smartweed, Persicaria pensylvanica (native) – Smartweed leaves can look similar to stiltgrass leaves, but smartweeds are not grasses. Smartweeds have small pink to white flowers, swollen nodes where the leaves meet the stem, and a thin membranous sheath that encircles the stem (this sheath is called an ocrea).
  • Large/hairy crabgrass, Digitaria sanguinalis (non-native) and smooth crabgrass, Digitaria ischaemum (non-native) - Crabgrass leaves do not have the white stripe on the leaves that stiltgrass leaves have. These crabgrasses are annual like stiltgrass. Crabgrasses commonly grow in lawns and other sunny areas.
  • Nimblewill, Muhlenbergia schreberi (native). Nimblewill is a perennial grass and its leaves do not have the white stripe on the leaves that stiltgrass leaves have.
 
 

Regulatory classification

Starting in January 2026, stiltgrass will be a Minnesota Department of Agriculture Prohibited-Eradicate Noxious Weed meaning that the above and below ground parts of the plant must be destroyed. Additionally, no transportation, propagation, or sale will be allowed.

Threat to Minnesota

  • Forms dense cover and outcompetes other plant species. The dense cover also makes it more challenging for tree seedlings to survive, which can negatively impact the timber industry.
  • Can increase fire frequency and fire intensity because it is an annual plant that dies back each year leaving large amounts of flammable material.

What you should do

One way that invasive plant seeds and fragments can spread is in soil. Sometimes plants are planted purposefully. You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals & mud from boots, gear, pets & vehicle.
  • CLEAN your gear before entering & leaving the recreation site.
  • STAY on designated roads & trails.
  • PLANT non-invasive species.

Native substitutes

 

Control methods

Note that stiltgrass is a high priority species for control in Minnesota. Please contact the Minnesota Department of Agriculture’s Noxious Weed Program for advice about stiltgrass management in your situation.

 

Mechanical control can be done by cutting or pulling the plant by hand or with equipment such as rakes. Pull before the plants have gone to seed. Pulling will need to be done repeatedly over many years to exhaust the seedbank. See the Minnesota Department of Agriculture noxious weed disposal website for additional information about what to do with pulled plants.

Herbicide control can be done using spot applications of 2 percent glyphosate. This is a systemic herbicide which is taken up by plants and moves within the plant, which can kill leaves, stems, and roots. Apply the herbicide during the summer before the plants go to seed.

Reporting

Report new occurrences by submitting a report through EDDMapS, emailing Report A Pest, calling Report A Pest (1-888-545-6684), or contacting your local county agricultural inspector.

Resources

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