Yes Pull! Now is the time to pull out Japanese stiltgrass, Microstegium vimineum. This invasive species is rampant in the eastern U.S. from Georgia to Massachusetts and west to the Mississippi River. It affects home landscapes and natural area alike. Here in the Mid-Atlantic region the grass is putting on a growth spurt prior to going into bloom. So the plant is expending a lot energy now to grow taller and produce flowers. It also means that it is a lot easier to pull out without getting on you knees. Since this grass in an annual, keeping it from going to seed can go along way to controlling its spread and reducing its numbers.
Early in the growing season Japanese stiltgrass stays relatively low, rooting at several nodes along the stem. In late July it starts growing upward to gets its flowers higher off the ground. If it were only that simple. Stiltgrass not only produces flowers at the top of the stem it also has flowers at most of the vertical leaf nodes buried within the stems. These are referred to as cleistogamous flowers.
Here are some highlights of my nearly 10-year battle with stiltgrass here in Maryland:
Pre-emergent herbicides are very effective in existing lawns and smooth surfaces. These chemicals interfere with the development of germinating seeds but do not have a strong effect on established plants. These must be applied in early spring prior to the germination of the stiltgrass seeds. I have been using a preemergent containing Dimension (dithiopyr) for several years. I took two years of successive treatments to get nearly complete removal of stiltgrass from the lawn in treated areas. Moss has not been effected.
Late summer pulling of previously uncut stiltgrass, especially in shady areas, has reduced the amount of stiltgrass in subsequent years. This does require a multiyear effort. Since nasty things like poison ivy, multiflora rose and wineberry can hide in the tall stiltgrass, it is important to wear gloves and arm protection when pulling.
After about 30 minutes of labor you can see the existing plants reappear. (Some of the freshly pulled stiltgrass is piled in the foreground-left.) |
Identify and plant native species that can compete with stiltgrass. Two exceptional plants that seem to outcompete stiltgrass are golden ragwort (Packera aurea), and mayapple (Podophyllum peltatum). Other plants that are strong competitors include clearweed ( Pilea pumila) and grasses that grow well in shade: river oats (Chasmantheum latifolium), mannagrass (Glycera sp.), Virginia wildrye (Elymus virginicus), and nimblewill (Muhlenbergia schreberi). Also there are a number of sedges that will persist under cover of stiltgrass and can form a dense cover if given the chance. Rosy sedge (Carex rosea) is one example that does quite well on my property. I recently noticed that there was much less stiltgrass growing in an area where celandine poppy (Stylophorum diphyllum) and mannagrass have been spreading. The exclusion of stiltgrass is not as great as with Packera, but it is noticeable.
This opening under the trees is free of both garlic mustard and stiltgrass now. In early spring it is fully covered with mayapples and a few woodland phlox. |
Japanese Stiltgrass Control
Season | Actions | Pros | Cons | Comments |
Late Winter Early Spring | Pre-emergent treatment | Effective in lawns and smoother (even) surfaces with access to soil surface. Allows lawns and perennials to get a head start. | Will affect all germinating seeds for several months. Uneven coverage on rough surfaces. Application needs to be at the right time (same time as for crabgrass). | Takes at least 2 years to knock down seed bank to see significant progress. More time to complete elimination, if ever. Many pre-emergents for crabgrass control are also approved for Japanese stiltgrass (aka Mary's grass, on the label) |
Late spring-Summer | Herbicide | Grass selective herbicide leaves broad leaf plants and some sedges intact. Try products containing Fluazifop-p-butyl | Difficult to control collateral damage, especially with non-selective herbicides | Targeted application and use of selective materials may limit side effects. |
Late spring-Summer | Pulling | Non-toxic and selective. Opens space for other species. | Labor intensive; left over stilt grass will expand to fill gaps. | If removal is not complete this will need to be repeated at the end of summer |
Late summer/Early fall | Cutting/ pulling/ burning | All methods to reduce the amount of seed | Need to complete actions before seed begins to ripen. | Copious amounts of seed being produced, need to be thorough and avoid spreading any ripened seed. |
You can read more information about my on-going battle with Japanese stiltgrass in previous blog-posts by entering 'Microstegium' in the 'Search this Blog' box at the top of this page.
Good luck and I would like to hear about your experiences battling this invasive species.