reseeding- with weeds?

Discussion in 'Turf Renovation' started by godjwood, May 14, 2009.

  1. godjwood

    godjwood LawnSite Member
    from RI
    Messages: 137


    I am redoing a section of lawn for a customer. it is filled with weeds and pretty much no grass.

    in the past I have spread topsoil on top of the grass (about 2 inches) and seeded and the other seed comes through.

    however, i am not sure what to do in this situation. if i rototil the weeds and the soil i am afraid that it will cause weeds to come in.

    If i spray the weeds then reseed i think i have to wait a couple weeks before i can seed?

    what would be your approach to this. it is about a 15x40 foot area.

    should i just dump topsoil on top of everything?

    please give me your suggestions.

    thank you.
  2. bigslick7878

    bigslick7878 LawnSite Senior Member
    Messages: 809

    Round up breaks down pretty quickly,usually in a week.

    You dont need to wait any longer than that.

    I would highly recommend NOT just throwing top soil over existing weeds.
  3. White Gardens

    White Gardens LawnSite Fanatic
    Messages: 6,776

    I would spray the weed and wait at least two weeks. Some Glyphosates suggest waiting to seed for up to 30 days.

    But yes, you should get the weeds under-control first, otherwise they will smoother out any grass seed that germinates.
  4. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,806

    Roundup is inactivated by soil--the dirt. You can't even use it with muddy water because it sticks to soil particles and is ineffective after that. It only works when it hits green plant tissue. In theory you could reseed the same day. Consider Roundup and then slit seed. Or...roundup followed by double dethatching, seed then rake it in. You should be sure to expose at least 50 percent loose soil. Possibly you could substitute core aeration for power raking, but there may not be enough seed-to-soil contact. Use high quality seed. It is normal for new seedings to be weedy due to weed seeds in the soil, be ready to spray weeds in about 8 weeks.
  5. Runner

    Runner LawnSite Fanatic
    Messages: 13,497

    If you are just overseeding and raking it in, spray them, (and yes theoretically you could seed right away - Riggle is absolutely correct on this). The next step I would do in your situation, is wait about a week while the weeds turn brown (they are actually dead long before that), just to make sure you got them all. Then, do your reseeding, and working it into the soil. A week later (but no later), respray it with gly for good margin. This will do two things - it will kill any new weed growth that perhaps didn't die all the way and may have had rhyzomes underground, and will help the new seed germinate easier and faster. Do not wait any later than one week to do this follow up though, as the new seed will begin germinating shortly after that. Also, make sure you use starter fert.. It makes a huge difference. The rest (and the most important part) is in proper watering.
  6. godjwood

    godjwood LawnSite Member
    from RI
    Messages: 137

    by spraying it with "gly" do you mean a weed killer like razorburn or roundup? and if i spray a week after wont i be spraying the new grass that is just starting to sprout? how will this make the seeds germinate faster?
  7. bigslick7878

    bigslick7878 LawnSite Senior Member
    Messages: 809

    Yes,its just a fancy name for Round Up.

    I think he didnt see the part where you said it was pretty much all weeds,and you are killing everything and not just the weeds.

    Just spray once,and then reseed.

    2 months after you seed you can then spray the weeds that will inevitably come in with the new seed.
  8. Runner

    Runner LawnSite Fanatic
    Messages: 13,497

    Actually, what I meant was - to put the seed down, then spray it with gly (Roundup). I mentioned to do it a week after the seed was down...but no later. The reason for this, is that within a weeks time, none of the seed will yet be germinated. Anything much past that, and there IS a risk of killing some potentially germinated new grass. Also as stated, the seed will start germinating after that.
    The spraying of the glyphosate on the area a week afer that will do two things; It will get any areas that may have been missed in the first spraying (will be more identifiable), and it will help the new seed germinate faster and easier.
  9. godjwood

    godjwood LawnSite Member
    from RI
    Messages: 137

    thanks, i appreciate all the help guys.

    i am planning on doing this job tomorrow, since we dont have much work lined up and i just got the go-ahead today. This is what i quoted the guy:

    "Rototil and clean rocks out of area to be seeded. Deliver and spread 4 yards of high quality topsoil. Spread shady mix lawn seed, apply Tupersan starter fertilizer to prevent crabgrass and cover with peatmoss."

    so what you are telling me is that i can actually spray seed with weed killer before it has germinated and it will still grow? thats crazy, i wouldnt have thought that was possible.

    So what i had in mind was to spray the weeds, then go out and get the topsoil, and put it on top. Will this be effective? or will the soil render the weed killer ineffective even after it is sprayed on the green weeds?

    i dont want to back out of the topsoil at this point because I have already quoted the customer for it.
  10. godjwood

    godjwood LawnSite Member
    from RI
    Messages: 137

    hmm.. afterthought.. if i am putting down 2-3 inches of topsoil on top of the weeds.. will the weeds really grow through that? wont it just smother them?

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