Stiltgrass in Yard - Ask Extension
Hello.
I am hoping to find some advice as to how best remove japanese stiltgrass or outcompete it in my yard. My preference is to avoid herbicides ...
Knowledgebase
Stiltgrass in Yard #878456
Asked July 23, 2024, 3:41 PM EDT
Hello.
I am hoping to find some advice as to how best remove japanese stiltgrass or outcompete it in my yard. My preference is to avoid herbicides if possible, but the stiltgrass seems to be getting worse every year and has exceeded my capacity to pull by hand. Would you recommend an herbicide prior to it going to seed if necessary? Additionally, I do plan on overseeding with fescue in late August to fill in some of the bare areas where the stiltgrass has taken over but I'm unsure if the fescue will be able to compete with the stiltgrass if it is still present. I'm ultimately looking for a strategy that is environmentally friendly while still effective. My goal in the coming years is to slowly minimize the lawn, but the stiltgrass is heavily present in an area that will likely remain turf grass. I can provide pictures if necessary.
Carroll County Maryland
Expert Response
No pictures needed. Japanese Stiltgrass is a widespread and frustrating invasive weed. I just started getting it in my lawn in the last couple of years. The only good thing about it is that it is easy to pull and is an annual plant that dies back completely each year and starts again from seeds left behind within the soil.
If you want to totally avoid the use of chemicals and are able to do it, there is some evidence that letting it grow tall during the season and then weed wacking it back just as it begins to flower can stop seeds from this years crop... however, the seed bank within the soil can keep going for a few years.
You could heavily overseed or even better, do a lawn renovation (or more expensive, sod) this late summer into fall to get a thick cover of turf grass started and then use a
pre-emergent granular herbicide in the spring, which stops seeds from germinating. (This is most often used for crabgrass control but a couple of weeks earlier for the germination period for stiltgrass). This page can tell you more- you want just the preemergent, not a 'weed-n-feed' product as we generally don't recommend fertilizing lawns in spring but fall.
https://extension.umd.edu/resource/japanese-stiltgrass-home-landscapes/
Here is our lawn renovation and overseeding info:
https://extension.umd.edu/resource/lawn-renovation-and-overseeding/
That said, your idea of replacing areas of turf-grass is a good one:
https://extension.umd.edu/resource/lawn-alternatives/ as they are pretty sterile environments that don't contribute to the health or biodiversity of the environment.
I'm not sure what I will do about mine... after all is said and done it may be a fact of life that the invasive is here to stay.
Christine
If you want to totally avoid the use of chemicals and are able to do it, there is some evidence that letting it grow tall during the season and then weed wacking it back just as it begins to flower can stop seeds from this years crop... however, the seed bank within the soil can keep going for a few years.
You could heavily overseed or even better, do a lawn renovation (or more expensive, sod) this late summer into fall to get a thick cover of turf grass started and then use a
pre-emergent granular herbicide in the spring, which stops seeds from germinating. (This is most often used for crabgrass control but a couple of weeks earlier for the germination period for stiltgrass). This page can tell you more- you want just the preemergent, not a 'weed-n-feed' product as we generally don't recommend fertilizing lawns in spring but fall.
https://extension.umd.edu/resource/japanese-stiltgrass-home-landscapes/
Here is our lawn renovation and overseeding info:
https://extension.umd.edu/resource/lawn-renovation-and-overseeding/
That said, your idea of replacing areas of turf-grass is a good one:
https://extension.umd.edu/resource/lawn-alternatives/ as they are pretty sterile environments that don't contribute to the health or biodiversity of the environment.
I'm not sure what I will do about mine... after all is said and done it may be a fact of life that the invasive is here to stay.
Christine
Thank you for the extensive response, Christine! The stiltgrass certainly does seem to be here to stay- the woods behind my house are being overrun by it. Do you have an idea of approximately when it goes to seed? The overseed and pre-emergent plan might be what I need to do, but timing will likely be critical. I want to overseed at a time when it won't need to directly compete with the stiltgrass. I also would like to avoid anymore stiltgrass seed distribution, but that will be tough.
Finally, I do want to avoid herbicides if possible, but given the situation, would some spot applications be appropriate or is the environmental impact too great? I also have children who play outside. I'd be happy to share my results if you need some insight about its presence in your yard!
Finally, I do want to avoid herbicides if possible, but given the situation, would some spot applications be appropriate or is the environmental impact too great? I also have children who play outside. I'd be happy to share my results if you need some insight about its presence in your yard!
Documentation of "fruiting" (ripening seed in this case) for Stiltgrass in Maryland suggests that it ranges from early September to late October across the state. (We don't have more local data, though weather may play a role as well in seed maturation timing from year to year.) Late August or early September would be a good time to overseed with fescue, having cut short the Stiltgrass (and the rest of the lawn in any areas it has infiltrated is okay) just prior to seeding the turf to not only remove the seed heads before they ripen and release seeds, but also to prevent spreading ripe seed around with a mower.
Herbicide should not be needed if you intend to try mowing-off much of the Stiltgrass growth before seed ripens and falls. Otherwise, an organic "knock-down" type of herbicide (that is, a contact-type and not a systemic) might be useful to kill the above-ground growth to weaken the plants. The consequence, though, will be that desirable turfgrass foliage contacted by such a spray would probably be damaged as well, though since turfgrasses are perennial (and cool-season turfgrass would be in one of the peaks of its seasonal growth that time of year), it will recover. (As an annual, Stiltgrass would have fewer root energy reserves for regrowth, though it still may grow back until frost kills it later, since it is tolerant of mowing, which accomplishes essentially the same thing -- temporarily removing top growth. Given that similarity, there's probably no need to bother with herbicide.)
Organic pesticide ingredients (herbicides included) generally tend to biodegrade faster than synthetic pesticide ingredients, so overall would tend to have less environmental impact, as long as the product label usage directions are followed. Like several synthetic herbicide ingredients, though, organic versions are fairly non-selective, meaning they can potentially damage any plant they contact, so application methods still need to be careful.
Miri
Herbicide should not be needed if you intend to try mowing-off much of the Stiltgrass growth before seed ripens and falls. Otherwise, an organic "knock-down" type of herbicide (that is, a contact-type and not a systemic) might be useful to kill the above-ground growth to weaken the plants. The consequence, though, will be that desirable turfgrass foliage contacted by such a spray would probably be damaged as well, though since turfgrasses are perennial (and cool-season turfgrass would be in one of the peaks of its seasonal growth that time of year), it will recover. (As an annual, Stiltgrass would have fewer root energy reserves for regrowth, though it still may grow back until frost kills it later, since it is tolerant of mowing, which accomplishes essentially the same thing -- temporarily removing top growth. Given that similarity, there's probably no need to bother with herbicide.)
Organic pesticide ingredients (herbicides included) generally tend to biodegrade faster than synthetic pesticide ingredients, so overall would tend to have less environmental impact, as long as the product label usage directions are followed. Like several synthetic herbicide ingredients, though, organic versions are fairly non-selective, meaning they can potentially damage any plant they contact, so application methods still need to be careful.
Miri
