As a summer annual plant, Japanese Stiltgrass germinates in spring, so it's likely that young plants escaped notice until they reached maturity this time of year, rather than very late-germinating plants only appearing recently. Can deer enter the meadow? They are thought to be a primary way the plant spreads via seed (other than a built-up seed bank already in place, which might germinate any time the soil is disturbed), where the seeds can cling to their leg fur or hooves. If it is feasible due to the size of the space and costs, try excluding the deer with fencing to reduce how much Stiltgrass is reintroduced to the area after you get the current population under control.

Additionally, as an annual, the Stiltgrass will die out this winter, even if you take no action now. Ideally, the grass would be removed before it can go to seed, but mowing this time of year is both impractical for meadow management and not able to completely remove the potential for the grass to go to seed, since Stiltgrass is capable of producing seed stalks close enough to the ground to be missed by a mower.

To discourage the germination of its seeds next year, you might need to resort to applying a pre-emergent. There are some active ingredients that work on grassy weeds while leaving broadleaf plants unharmed, though those would probably also hamper warm-season grass germination (if you have any desirable grasses in that category that you are relying on self-sowing to fill in.) Otherwise, covering any bare ground with a groundcover (if one isn't already a component of the meadow) would be the best approach, as that will help to out-compete Stiltgrass seedlings before they can establish. You may be familiar with "matrix" planting, which uses a foundation like a ground-covering species (or, ideally, a mix of a few species for better resilience) that taller plants are sown/planted into. The matrix plant(s) fill-in any gaps between those larger clumping plants so it acts like a living mulch.

Research is ongoing as to which, if any, organic herbicides suitably control Japanese Stiltgrass as post-emergent options. So far, trials with iron-based herbicides, for example, are not encouraging. Corn gluten can be an organic option as a pre-emergent herbicide (in areas that are not lawns), but it is non-selective, so any desirable seed germination would likely be suppressed as well. However, the timing of application -- early spring for weedy grasses like Stiltgrass and Crabgrass -- might limit how much impact it has on any later-germinating desirable plants in the meadow. This is not an approach we have experience with, so cannot say how successful it would be. If you try it, follow all product label directions on the package, and be aware that corn gluten serves as a nitrogen fertilizer source as it breaks down, which might not be advantageous for native species that grow and compete with weeds best in lean soil. It also might need to be applied twice to catch Stiltgrass seedlings that can sprout in mid-spring or so.

Fortunately, Stiltgrass probably wouldn't out-compete established perennials since it only has a one-year life cycle and each plant is fairly small compared to the biomass of most mature perennials, but it might be more of a threat to annuals or short-lived perennials that you are relying on self-seeding to maintain their presence in the meadow.

If you'd like to hire a consultant, persons with Chesapeake Bay Landscape Professional training, which teaches sustainable landscaping techniques (that can include meadow creation and maintenance), may be a good starting point.

Miri

You're welcome. Unfortunately, Japanese Stiltgrass is found in every county in the state, and as you noted, is common along trails (both human and animal) in many of our parks and woodlands. Good luck!