Japanese stiltgrass can be hard to control
For a number of years, my husband and I have been trying to control Japanese stiltgrass in our lawn. I hate it. It tends to grow very densely and I don’t like the way it looks. More importantly, it is extremely invasive, spreading into wild areas and choking out native plants. We try not to use chemicals, though we have applied a pre-emergent in the past. It seems chemicals are the only way to control it because we’ve found it impossible to pull all of the stiltgrass out of our lawn. We’ve been overseeding with lawn grass seed and we fertilize with an organic lawn fertilizer. This year, we thought the lawn looked better, until recently when the stiltgrass quickly grew and spread. So, I referred to the following Penn State article: https://extension.psu.edu/controllingjapanese-stiltgrass-in-your-garden
While the article mentions pulling the stiltgrass to prevent seed production, it doesn’t suggest any type of tool that might help with this task. I’ve considered purchasing a powered dethatcher, but I’m not convinced that would work. Do you know whether or not it would? We’ve tried a manual detaching rake. Beside the fact that it’s physically difficult to use, the sharp metal tines tend to cut the stems, so it doesn’t remove all of the stiltgrass. Can you suggest a tool that is (hopefully) a little easier to use, but is more effective for pulling up the mats of stiltgrass in our lawn? Thank you. — Anna Grunwald The Penn State article is quite thorough. Japanese stiltgrass (Microstegium vimineum) is a very invasive and difficult to control weed. The grass grows one foot to three-feet tall and produces spreading mat. Although it is an annual, it can produce thick mats of thatch that will smother other competing vegetation. The leaves, arranged alternately on the branched stake, are about one inch to three inches long and bright green. There is a silvery strip on the midrib of each leaf. The flowers appear at the top of the stalks and set seed in late August to September.
There is no hope of eradicating it. Control will take a multipronged approach. Anne has applied several of the control methods, but will need to employ them all in the same season. Japanese stiltgrass seeds quite freely and readily grows in most areas. The seeds, small, shiny and sticky, are spread throughout the landscape on the fur and hooves of animals, flowing or flooding water, and on the clothes and shoes of anyone who comes in contact with them.
Control stiltgrass spread by mulching ornamental beds and maintaining dense, healthy lawn. Avoid cutting grass very low, as it stresses the grass, and any bare spot or sparsely grassed location is a potential site for stiltgrass to grow.
Hand-pulling is a good control for small patches.
The grass is shallow-rooted and easily removed. Remember that since this opportunistic weed grows well in disturbed soil, areas recently weeded will have a regrowth, as seeds already in the soil are stimulated to germinate.
Large patches should be mown in August after the flowers have appeared, but before the seeds are mature. Ideally, bag and dispose of clippings. Cutting earlier in the season will result in shortened plants that still develop seeds. Note that plants, particularly mature ones, should not be composted.
Pre-emergent herbicides are of some use, but will only kill those seeds that germinate that season. Note that stiltgrass germinates several weeks before crabgrass, so any herbicide should be timed to that event. Seeds are viable in the soil for several years (about five). Post-emergent herbicides are effective, but generally non-discriminative, killing whatever they touch, and are environmentally damaging in many cases.
As far as dethatching, I would not worry if the roots are not removed, as the grass is an annual and will die off at the end of the season. Dethatching will help remove the dense mats that develop in heavy infestations, but if the plants have matured, it will also disperse the 100 to 1,000 seeds that each plant can produce. Dethatching will also disturb the soil and, as previously mentioned, result in a new crop of weeds from previously dormant seeds in the soil.
Control must employ several methods. Cutting before seeds mature, mulching beds, dethatching will combine to decrease the number of plants. However, no method or combination of methods will be effective unless it/they are employed annually.
Another descriptive and informative site is: https:// extension.umd.edu/hgic/topics/japanese-stiltgrass, from the University of Maryland Extension website.