Japanese stiltgrass remediation - Ask Extension
Hello - During a Bay-Wise visit we saw large areas of Japanese stiltgrass on a steep slope in Critical Areas. (See photo.) What is your recommendation...
Knowledgebase
Japanese stiltgrass remediation #873916
Asked June 20, 2024, 12:28 PM EDT
Hello - During a Bay-Wise visit we saw large areas of Japanese stiltgrass on a steep slope in Critical Areas. (See photo.) What is your recommendation for eradicating it please? Would a deep covering of wood chips over sheered back foliage be effective? Are there any native plants, such as Packera aurea, that are proving to be effective in out competing it?
Thank you!
Anne Arundel County Maryland
Expert Response
Any plant removal, planting, and soil disturbance or erosion potential in a Critical Area might need to be approved by local government before taking action. Japanese Stiltgrass is a summer annual, and since it dies by winter, only the prevention of new seed germination would be needed to keep it from taking over again the following year. Deer and other wild animals also likely help to move seeds around by inadvertently carrying them on their feet or fur, so deer exclusion, while important for private properties, isn't a practical approach in natural areas or for large expanses of land.
Establishing a native, aggressively-spreading groundcover might help with annual weeds like this; it's not necessarily effective combatting established perennial weeds, in case they turn up later. We recently overhauled our groundcovers page and included several species lists of native plants that might be suitable for certain locations (sunny and damp, shady and dry, etc.). They are not exhaustive lists, but provide options and ideas to get someone started.
We don't know if a wood chip layer over mown-down Stiltgrass would be sufficient. It probably would smother it well enough if the layer could be around 8 inches or so thick, but on a slope, that depth might not stay in place. There are paper-material landscape "fabric" options, which biodegrade, but we don't know if its use would be permissible in a Critical Area, though at least it would help suppress erosion until new plantings establish. Any such mulch would be compatible with planting plugs or older plants, since it can be moved aside (or cut, for the paper or burlap) to install individual plants, but it would not be useful if you intended to seed the area with natives, so that might be a greater revegetation cost to consider with the project.
Miri
Establishing a native, aggressively-spreading groundcover might help with annual weeds like this; it's not necessarily effective combatting established perennial weeds, in case they turn up later. We recently overhauled our groundcovers page and included several species lists of native plants that might be suitable for certain locations (sunny and damp, shady and dry, etc.). They are not exhaustive lists, but provide options and ideas to get someone started.
We don't know if a wood chip layer over mown-down Stiltgrass would be sufficient. It probably would smother it well enough if the layer could be around 8 inches or so thick, but on a slope, that depth might not stay in place. There are paper-material landscape "fabric" options, which biodegrade, but we don't know if its use would be permissible in a Critical Area, though at least it would help suppress erosion until new plantings establish. Any such mulch would be compatible with planting plugs or older plants, since it can be moved aside (or cut, for the paper or burlap) to install individual plants, but it would not be useful if you intended to seed the area with natives, so that might be a greater revegetation cost to consider with the project.
Miri
