I recently attended the Connecticut Invasive Plant Conference at Uconn. In the afternoon, there was a panel discussion about invasive plant control and a question was posed regarding the control of Japanese Stilt Grass in a large wildflower meadow type landscape. The guy felt his garden was doomed due to the invasion of Japanese Stilt Grass. He’d tried everything and he losing the battle and eventually would lose his beloved garden. His question was how would you control Japanese Stilt Grass in a large planted meadow. All 3 professionals who were on the panel were looking at it as post control. I mean, that was how the question was posed. “Stilt Grass is taking over my large garden, I’ve tried everything and I’m losing the battle”. The discussion went on for 10-15 minutes and the answers from the experts were driving me crazy. There are many post emergent herbicides you could use to kill the Japanese Stilt Grass but as the person with the problem communicated, it’s a large area with dense plantings. It was virtually impossible to apply post emergent herbicides without killing a lot of desirable plants and without each application taking days to apply. The person with the problem chimed in and said to selectively stop spray the Stilt Grass out of this garden would take months, trying to spray the weed yet avoid the desirable plants. Then chemicals were suggested that would knock down the grass and damage the perennials/shrubs but it wouldn’t kill them. Another thought was to use a propane torch to selectively damage the grass. What? If you’ve ever tried to flame a garden or driveway, it takes forever and it’s not that easy to pinpoint extreme heat to select areas. Torching is more like using a non selective herbicide. Expect to kill a lot in a densely planted garden.
Half the battle with eradicating invasive plants is to know how they grow, how they survive and what their life cycle is. Unlike Knotweed and Mugwort, I feel that Japanese Stilt Grass is a relatively easy plant to figure out and control. Well maybe not control as in eradicate but at least to manage and let’s face it, invasives are here to stay. With invasives, it’s all about management even if the goal is total eradication.
Japanese Stilt Grass is an annual. It does not survive our winters and needs it’s own seed, to germinate year after year. You could physically pull the plant but this creates another problem and that’s soil disturbance. Disturbing the soil is not something you want to do in a meadow planting. Why? Because soil disturbance brings new weed seeds to the surface, perpetuating the problem or worse, a new problem. You could cut the plant, leaving the roots undisturbed. Japanases starts setting seed in August so cutting the plant low in August and keeping it low through the first frost would be a good strategy but the area sounded too large for this approach. The only real way to address the problem, something the presenters never even touched on until I posed the questions was to broadcast a pre-emergent herbicide over the entire meadow. Unfortunately, it wouldn’t allow any wildflower seed to germinate as well but I feel like this is really the best approach in a situation like this.
After a couple of seasons, I would slowly dial back section by section to see how much Japanese Stilt Grass comes back and then and cut and remove what comes back.
