Organic Spray for lawn prior to overseeding

Question: We just bought a house and the the whole yard is essentially goosegrass and other grass weeds, we have made garden beds and have planted natives but still need a lawn and are planning on aerating and overseeding in the fall. Do you have any recommendations for a organic spray that wouldn't hurt the ecosystem/runoff to the bay to spray on the lawn areas prior to overseeding or do you just recommend spraying an herbicide one time and be done with it? The lawn size is too big for using a flame. We are not planning on using any harsh chemicals on the lawn after that. Any recommendations are appreciated.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied August 12, 2024, 2:47 PM EDT
response: It's hard to ID the weedy grasses from the photo, though some of them may be Crabgrass instead of Goosegrass. Both species are annual and will die once it freezes later this autumn, and by overseeding the lawn to thicken it up, that will help to out-compete their seedlings should they germinate next year.  If you wanted to kill the existing weeds before seeding, which will help get the foliage out of the way (since good seed-to-soil contact is essential for good germination), you can use any of a variety of options among organic herbicides, especially those that include grasses on their label (as opposed to only broadleaf weeds). Organic herbicide ingredients will generally be non-selective, meaning they will damage anything the spray contacts, so use them with caution around any patches of good turf or other landscape plants. Perennials accidentally hit with spray should regrow, since organic herbicides also tend not to kill any weed roots since they are not systemic (they're contact-only, so only affect the plant parts they contact directly and are not absorbed). While you could use a systemic synthetic/conventional herbicide to kill the roots of the weeds treated, that might not be necessary if they're annuals and not likely to regrow much (if at all) after a "burn-down" treatment with a contact-type chemical.  Extension doesn't have information on all the various organic lawn herbicides on the market at any given time, but since most of Montgomery County restricts lawn pesticide use, they have some products listed online which are organic and permitted under their regulations, in case that's helpful (see linked page). Our Organic Lawn Care page might also have some tips that prove useful.  In the meantime, try to have a laboratory soil test performed so you can learn if applying a certain fertilizer type (with or without phosphorus, essentially) and lime would benefit the new lawn. When ready to overseed, try to use a blend that includes as many (even if it's just one, which is sometimes all you can find) of the recommended turf cultivars as possible, particularly of tall fescue, which will help to keep the lawn resilient to typical stresses and diseases. (The 2023 edition of turf cultivars is up now, but will be replaced with the 2024 version as soon as it's published, which won't be long now.)  The pages linked above contain lots of info (and we have plenty more lawn care and maintenance web pages as well), so while it might seem overwhelming at first, you can refer to them as you're ready to proceed and hopefully they're helpful.  Miri

responder: The Question Asker Replied August 12, 2024, 4:14 PM EDT
response: Thank you Miri for the in depth answers, I wasn't expecting 1/8 of the information you provided, it is greatly appreciated.   I'll probably use a vinegar based post emergent herbicide on the crabgrass/goosegrass combo and avoid any of our bedding plants.   I'm planning on aerating before I seed too so hopefully that will help with germinations of the seed blend, planning on using the DelMarva Johnathan Green mix to avoid a monoculture and best chances of survival. I'll do the soil test too, thanks again for all your help, it was appreciated. Regards,  Ian   On Mon, Aug 12, 2024 at 2:47 PM Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied August 12, 2024, 4:22 PM EDT
response: You're welcome!  A cautionary note regarding vinegar as an herbicide: use only a product that is labeled as a weed killer (that is, not household food or distilled/cleaning vinegar). Herbicide vinegars, more appropriately referred to as acetic acid to differentiate them from consumable vinegars, are a much stronger concentration in order to function well, and as such, can be very caustic and hazardous to use, even if considered a more "natural" or organic type of weed control option. Skin and eye protection are a must, and do not apply during breezy or hot weather, or what evaporates could easily damage nearby plant foliage, even if not directly contacted by the spray.  And yes, core-aerating is a good method for alleviating soil compaction if done just prior to seeding, and it can improve seed-to-soil contact as well given the soil plugs brought up to the surface.  Miri

responder: The Question Asker Replied August 12, 2024, 4:33 PM EDT
response: No worries, Miri. I was thinking more along the lines of Green Gobbler, a lower density vinegar based herbicide and then waiting 4 weeks before aerating and seeding. Thanks again.  https://www.homedepot.com/p/Green-Gobbler-1-Gal-20-Vinegar-Weed-Killer-G6008/317909972    Regards,  Ian   On Mon, Aug 12, 2024 at 4:22 PM Ask Extension <<personal data hidden>> wrote: