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Sowing a lawn organically seems to have 2 problems that need solving:

  1. Killing the weeds prior to sowing
  2. Avoiding weed growth after sowing

Once the soil is levelled, I'm considering trying the false seed bed technique to kill off any remaining weeds before sowing grass. Wikipedia's article on false seed beds suggests hoeing the soil after 2 weeks, and probably repeating that step again at least once to be sure. If the technique is repeated enough, perhaps weed growth after sowing can be mostly avoided?

Has anyone had experience sowing a lawn with the false seed bed technique? Is there any other advice that might be useful?

Background:

I have recently built a house and the earthworks have resulted in approx 180sqm of a bumpy and difficult mixture of soil and pebbles around the house that I'd like to be lawn.

I know there are heaps of weed seeds in the soil as lots have sprouted over the last few weeks. Our first step will be to have the land levelled with a small digger as there's too much soil to shift by hand - this will hopefully kill off most of the weeds currently growing on the surface, but I'm sure it will also expose more weed seeds.

I have obtained quotes from tradesman for sowing the lawn, but they want to spray with a broadleaf herbicide several weeks after sowing to kill off weeds. Researching the ingredients in the proposed spray (picloram being one), they appear to be very safe in the short term but very little appears to be known about long term effects. It is also toxic to aquatic life, will readily drain through soil into the groundwater (our region uses mostly groundwater for irrigation and drinking!), is long lived, and may affect plant growth when it ends up in our compost. Interestingly, picloram also appears to be considered inappropriate for residential use. Going organic seems like a sensible option!

Thanks!

Update: I hoped the grass would win competing against other plants. After having some issues with birds eating the seed on the day it was sown, I resowed some areas then sprinkled sieved soil over the whole area to protect the seed. It took about 3 hours to sieve enough soil.

Now, something like 10 months later I think, the grass is growing well, however clover is healthily coexisting with the grass. In a few parts which didn't get enough grass seed, the weeds, such as plantain and ox tongue, are much more prolific, so it's clear the grass is dominant enough to keep them down where well sown. I've dug out a few thistle and ox tongues that established themselves amongst the grass.

I'm allergic to beestings, so my daughter might be too, which is why we'd rather not have much clover around; it attracts lots of bees in summer. One suggestion I've had was to add nitrogen fertiliser to make the clover bolt and then die off. I'm not sure whether any organic fertilisers would be adequate for this, or whether I'd need to use a non-organic one such as superphosphate.

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    Not an answer, but IMO if you want an organic lawn, you have to tolerate some weeds. Avoiding weed growth after sowing is best achieved by having the lawn grow quickly and thickly so that it outcompetes the weeds. – bstpierre Nov 8 '11 at 1:56
  • Thanks for the update. I can't find any info on getting clover to bolt. In the past I remember having used an organic weed killer that was high nitrogen that did knock out some white clover. Haven't seen it since and can't remember the name. There are some organic liquid fertilizers but not many high in N. A combination of blood meal and one of them maybe? Do you fertilize the lawn regularly? That can help with density. Superphosphate is 0-20-0, it has no nitrogen. – OrganicLawnDIY Sep 10 '13 at 0:59
  • @OrganicLawnDIY, no I don't use fertilisers regularly. I don't know whether it would work better (if at all) to give a big dose once, or smaller doses over a longer period. Oops re superphosphate! I must be thinking of a different product that's very high in nitrogen; as I said I don't tend to purchases fertilisers! – Highly Irregular Sep 10 '13 at 1:25
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    Fertilizers will help keep the lawn thick and healthy. Depending on the type of grass you have, 3-4 pounds of nitrogen per year is typically recommended. If you mulch mow you are already returning about 1/3rd of the N back to the grass. Multiple applications are better. Don't apply more than 1lb of N in a given application. Early spring, late spring, early fall, late fall are when I usually fertilize. I read a study recently that using something like fish fertilizer sprayed regularly may provide the same benefits with much less actual N applied. – OrganicLawnDIY Sep 10 '13 at 14:10
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You could use corn gluten meal to control weeds. It is a germination inhibitor that lets the grass grow while keeping out the weeds.

However, don't put down corn gluten meal when you sow the grass seed, because it will inhibit germination there, which is exactly the wrong thing. Wait until the grass comes up!

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This is an old question but I'm curious what you wound up doing and how it worked out for you as I did something similar.

I documented in detail on my site my organic lawn renovation which I did last fall. I also used and reviewed some organic herbicides which worked pretty well.

My initial plan was to apply the herbicides in two rounds. Once to kill the existing grass and weeds, and another application to kill new weeds that germinated. I changed my plan based on manufacturer recommendations and I got some weeds during germination. I should have gone with my initial plan.

Another option is soil solarization which has the benefit of killing some pathogens as well but must be done when it's hot out. Usually summer.

I was unaware of the false seed bed technique. That seems like a viable option. Whatever you do, do something to kill the existing lawn and weeds, resurface the soil, then water to let the new weed seeds that have been exposed germinate, kill the weed seedlings somehow and then seed your lawn. Similar sequence as using roundup but use organic methods. I liked the organic herbicides but next time I might try combination of different techniques that would include them and possibly solarization. Spraying is easier than hoeing.

  • Thanks for the answer! I've added an update to the question, above. I do have some more levelling and sowing to do, so the additional information will be useful. – Highly Irregular Sep 10 '13 at 0:26

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