Dealing with Japanese Stiltgrass
The basic strategy for managing Japanese Stiltgrass is the same as for any non-native invasive plant:
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Prevent it (if possible)
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Aim for early detection and total eradication (if possible)
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If it is too late for that, figure out how to minimize the damage. That damage includes what happens when the seeds from your property spread to other people’s yards or into natural areas.
Prevention
Prevention may be impossible if there are infestations nearby, especially if they are uphill from your property. We bring seeds in on our shoes and clothes. But we also bring them in with plants that we acquire. Plant exchanges pose a greater risk than garden centers. Bags of turfgrass seed also may contain some weed seeds, as might mulch or compost. Lawn-and-landscaping companies move it around on their equipment.
Things that might help:
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Brush off shoes, clothes at the location where stiltgrass is present to minimize seed transport.
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Bare-root plants before bringing them and planting them in your yard,
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Creating your own compost and using leaves from your own yard as mulch may help as well.
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Deer management can be very helpful, since loss of native plants is a major contributor.
Early detection and eradication
Spreading by roots is not a problem with this annual grass. It only spreads when it starts to go to seed in mid August. You can prevent the reseeding then by pulling it up (it comes up easily) or by shaving it all the way to the ground with a string trimmer so it doesn’t have time to regrow and go to seed before frost. If you need help, the timing is convenient for teenagers looking to earn some cash before school starts. Each plant makes up to a thousand seeds, so you will need to get out every plant eventually, though not necessarily with your first go-round, if that seems like too much. If you get out the majority for a few years in a row, you may beat it back to the point where you can do a more thorough job.
If the stiltgrass is in a mowed lawn, it learns how to set seed very low to the ground. Preemergence crabgrass killer can be effective if applied very early in the season (December through March).
Since the seeds remain viable in the soil for as many as seven years, you may need to keep up the routine for a long time to see progress.
Mitigation
You may find that it is too late for complete eradication on your property if
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It is a long-established infestation.
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The area is larger than you can deal with.
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You are in a floodplain or other area where new seeds continue to wash in.
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You are unwilling or unable to use herbicide. Grass-specific herbicides cannot be used anywhere near water.
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Your site happens to be ideal for Stiltgrass.
It must also be recognized that there is an opportunity cost to working on Stiltgrass. In some cases, time spent trying for total eradication might be better used for controlling other invasive plants or for tending a native plant garden that attracts other people to the movement.
Strategies in this situation include
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Work from the outside in to try to contain spread to healthy habitats.
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Do whatever debulking you have time for.
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Prioritize areas where it is likely to spread into good habitat.
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Plant native plants thickly to reduce room for the stiltgrass to grow.
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Focus on areas where needed to prevent smothering of shorter native plants or to improve the aesthetics.
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Use native plants that are able to stand up to stiltgrass.
An accidental experiment
Before last year, this dry, sunny lawn had stiltgrass everywhere, evenly distributed, and was mowed regularly. Most of the original turfgrass had disappeared long since. Last year, the stripes that here look brown from the autumn stiltgrass were mowed regularly as paths, but except for the perimiter, no mowing was done elsewhere until fall. This year, only the perimter was mowed. Last year's paths are full of stiltgrass, but where the violets have taken over, very little Stiltgrass is growing.
Next year - who knows? We'll see.
Plants that can stand up to a field of Japanese Stiltgrass
Grasses
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Carex squarrosa (Squarrose Sedge)
(full sun to part shade, wet) -
Carex crinita (Fringed Sedge)
(full sun to part shade, moist to wet) -
Carex lurida (Lurid sedge)
(full sun to part shade, moist to wet) -
Coleataenia anceps (Beaked Panic Grass)
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Elymus species
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Paspalum laeve (Field Bead Grass)
(full sun to part shade, moist) -
Paspalum floridanum (Florida paspalum)
(full sun, moist)
For more information, see the Blue Ridge PRISM fact sheet.
Click here for an excellent and detailed webinar.
Forbs
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Cirsium discolor (Field Thistle)
(full sun, moist) -
Eutrochium fistulosum (Joe Pye Weed)
(full sun to part shade, moist to wet) -
Packera aurea (Golden ragwort)
(full sun to shade, dry to moist) -
Solidago rugosa (Rough-leaved Goldenrod)
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Symphyotricum novae-angliae
(New England Aster)
(full sun to part shade, moist) -
Vernonia noveboracensis
(New York Ironweed)
(full sun to part shade, dry to moist) -
Verbesina alternifolia (Wingstem)
(full sun to shade, moist) -
Viola sororia (Common Violet) (Prefers moist shade or part shade but can do quite well with more sun and less moisture)
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Zizia aurea (Golden Alexander)
(full sun to shade, moist to wet)