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We've got a ~4500sq/ft back yard that's probably 90% weeds. Is there an organic/natural way to kill off all the weeds so we can start from scratch? With kids and dogs and a swimming pool right beside the area, I'd really rather not spray a ton of roundup (or something comparable).

I had one guy suggest Iron X but I've read mixed reviews.

I've always read about people putting newspaper or black tarp over areas of weed to kill them, but with this square footage I'm just not sure that's feasible.

Here's a close up of what most of the weeds are (though really there are probably a dozen different types):

enter image description here

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Those are strawberries! –  Chris Cudmore Mar 8 '11 at 19:42
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@ChrisCudmore those are false strawberries (Potentilla indica, formerly Duchesnea indica). I have them too, and they are as bad as creeping charlie. –  J. Musser Feb 16 '12 at 2:39
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@jmusser: good id! I have them too, but only in areas where the soil hasn't been improved. They don't seem to spread into lawn that has been well fed and limed. –  bstpierre Feb 16 '12 at 22:28
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What's your long term goal for the area? Lawn? Vegetable plantings? Sod? –  Amanda Jul 9 '12 at 19:57
    
no-one mentioned steam? some councils here started using these steam backpack units instead of deadly copper (at those concentrations) maybe you can find one in a hire shop. –  Chris Aug 7 '12 at 15:46

16 Answers 16

up vote 28 down vote accepted

Well, I might argue that a tarp IS adequate. It is far better than a lot of chemicals, especially with kids & a dog.

Buy one large tarp. You can easily buy a 30x40 foot tarp for under $100. I saw one on Amazon for $59. You would probably spend that much money on chemicals anyway. 30x40 feet is 1200 square feet, or 1/4 of the square footage of your yard. So kill off one rectangle of weeds. This will take a few weeks. Then move the tarp to a new spot. After 4 placements of the tarp, the entire lawn is done. Clean up any small spots in the corners with a hoe.

And, if you look around, you might be able to find a larger tarp. I did just look, and I found a silver/black poly tarp for $65 that was 30x50 feet, so 1/3 of the footage of your lawn.

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Good point. Does the color of the tarp matter? I've found a 50x80 tarp for a reasonable price, but it's blue. Most places I've read say use black. –  Shpigford Mar 8 '11 at 22:50
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You'd need to plant grass seed right away after moving the tarp I think. Otherwise within a few days, you'll probably have weeds growing back again in the new bare patches. –  gregmac Mar 8 '11 at 22:53
    
The black tarp lets less light through (the blue ones tend to be rather thin, you might have to double it over), but also the black absorbs more light and the warmth helps to kill things off (although, I don't know that it'll get to the necessary temp you need to get to kill off most seeds, which is why gregmac's comment is important). Before planting, I also pull up the runners from plants so they have as easy of a time coming back. –  Joe Mar 9 '11 at 1:58
    
Also, consider multiple smaller tarps ... more easy to fit them into areas, and you can often find other uses for them later (eg. drop cloth). And you can then move one once it's done, while leaving another section for an extra week. –  Joe Mar 9 '11 at 2:01
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Black is good here. You want it to block light and even water, which any color tarp would do. But also important is the ability to absorb as much light as possible, to get hot and bake the weeds. So black is an important color here. –  user923 Mar 9 '11 at 4:03

This is a little strange, but I'll throw it out here anyways.

Around here there is actually a company that rents out goats to clean up large areas of unwanted vegetation. They come out with some hungry goats, the goats eat all the weeds right down to the ground, then they leave with the goats.

Not sure if there is anything similar in your area, but might be worth checking into.

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Haha, we've actually looked in to this but unfortunately our neighborhood HOA won't allow farm animals of any type to be present on your property. Though...wondering if I sneak them in for a few days if anyone will notice. Hmmmmm. :) –  Shpigford Mar 9 '11 at 19:20
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I can just see it now - "They're...um...dogs! Yeah, dogs. With mutant horns and hooves...and they eat grass." –  Doresoom Mar 10 '11 at 19:11
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I can't help but smile at the thought of large, horned "dogs" munching away. "Honest, they said these were dogs!" –  user923 Mar 10 '11 at 22:13
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Be careful about goats. I used to have them and they will not discriminate about what they eat. Mine ate 5 10' tall fruit to the ground, trunk and all! If you have any shrubs you want to keep this is a bad idea. Also, they are major escape artists, so expect to chase them down at least once a week. –  JohnFx Mar 14 '11 at 1:32
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Sheep would be safer and are less satanic looking. –  JohnFx Jun 6 '11 at 4:00

Vinegar works pretty well. Spray down, and within a few days they should be dead. I'd follow it up after a few days with a rototiller, rake, and seed.

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Almost sounds too easy to use vinegar. Seems like if it really worked that well, then everybody would be using it. –  Shpigford Mar 15 '11 at 4:10
    
I've used vinegar. It works pretty well, though not as dramatically as RoundUp. You can get stronger vinegar at feed stores to use as herbicide. It seems to work best in sunlight. –  Scott Saunders Jun 7 '11 at 19:26
    
I don't know how much, but I would think that vinegar will acidify your soil. Acid soil could be part of the root cause for the failure of lawn grasses to thrive and weeds to take over. I don't know if Potentilla indica does well in acidic soil, but strawberries (which are related) do like it. –  bstpierre Feb 16 '12 at 22:10
    
I think vinegar works well enough on some weeds for spot applications but I've found that it is only so-so for some weeds. It also is basically ineffective on weeds which spread via rhizomes. –  itsmatt Jun 9 '13 at 1:00

Something not suggested: sheet mulching for "lasagna" gardening.

A local department store will probably give you 4,500 sqft of cardboard boxes for free -- they may even deliver them! De-tape and de-staple them, break them down, and put them over everything you want to kill. Put a bit of topsoil on the cardboard to hold it down. The cardboard will eventually break down, enriching your soil.

Please don't use RoundUp. Despite claims here and in Monsanto's marketing literature, it is deadly poison to numerous things -- including people. In India, an epidemic of farmer suicides is coming from drinking RoundUp in protest over Monsanto's grip on their seed supply.

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A non-toxic way of killing off a patch would be to cover the area in a black, light-proof tarp.

The heat, combined with the lack of light and moisture, should kill anything under it.

Edit: Oops, missed the "4500 sq ft" part. You might be able to find some rolls of inexpensive material, like plastic wrap or roofing cover, but that's still a lot of material.

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Like I mentioned in the original post, due to the size of the yard (4500 sq/ft), covering the whole thing in tarp just isn't feasible. –  Shpigford Mar 8 '11 at 21:15

I had the same problem in our yard - 80% weeds, but wanted to avoid chemicals b/c of kids and dogs. Our yard was much smaller (less than 1000 sq/ft), but the solution worked well: I rented a gas-powered sod cutter, set it for a fairly deep setting and cut off the entire layer of grass/weeds. It's pretty hard work (especially hauling the sods pieces away).

This method avoids pushing weed seeds farther into the ground as would happen if you just roto-tilled. After cutting the sod, I tilled and then planted grass seed.

4,500 sq. ft is a ton of sod though...

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Another idea would be to flip the sod over and then cover with a tarp and solarize it. –  itsmatt Jun 9 '13 at 1:25

Good answers above. But one is missing:

Torch your weeds.

You can build your own torch (um, dangerous) or purchase one such as the Red Dragon.

But beware. According to this worthwhile read at Bifurcated Carrots, you should not use a torch near dry brush or over mulch, both of which can be extremely flammable. Also, a torch may not kill weeds that have matured past the cotyledon stage.

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+1 for the torch - very effective. I always wet everything down ahead of time and keep a sprayer of water available. The Red Dragon is what I have. Works well. –  itsmatt Jun 9 '13 at 1:31

You could kill the weeds with any of the other solutions already posted here, but if you don't cure the root cause as to why the weeds are outcompeting the lawn grass, they will just come back.

  • Before you kill the weeds, get your soil tested. At the very least, check the pH.
  • Then kill the weeds. (I think your best approach to killing the weeds will be multiple tarps.)
  • When the weeds are dead, spread lime as recommended by the pH test.
  • Spread at least 1/2" of compost (1" would be better). That's about 7 cubic yards -- get it delivered (or make a couple trips with your pickup truck) in bulk, don't try to buy bags from the local big box! This will feed your lawn. It's worth investing in quality compost: free composted horse manure, for example, may be loaded with weed seeds. Municipal compost, if available in your area, probably won't have this problem.
  • Seed your lawn. If allowed by your HOA, consider using a lawn seed mix that contains white clover. Clover draws nitrogen from the air and puts it into the soil; this helps to feed the grasses.
  • Follow the tips in this answer for ongoing lawn maintenance. If you keep your grass healthy it will outcompete the weeds and you won't have this problem again.
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As noted in my comment above, those are strawberries. Think about preserving a patch.

Roundup is not a bad idea, unless you live near a swamp/waterway, as it is toxic to amphibians. I'd just spray, and go visit the parents for a weekend.

Other than that, your best bet is to roto-till and pull up as many roots as possible by hand, and then re-sod.

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+1 for preserving the strawberries ... but I can't agree on the RoundUp, partially because I'm against Monsanto's behavior when it comes to seeds. –  Joe Mar 9 '11 at 1:57
    
Joe, is there any other reason you can't agree on RoundUp? I can't say I really care about Monsanto's behavior here...I just want something that works. –  Shpigford Mar 9 '11 at 14:50
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@Shpigford : I'm also in a semi-rural wetlands area, with lots of wildlife and farms down stream from me, so against herbacides in general ... but I'm particularly against Monsanto's products for what they've done both with their seeds and suing neighboring farmers and getting farmers using their seeds to indiscriminantly spray herbacides. –  Joe Mar 9 '11 at 15:49
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@Shpigford I'm with Joe.You should watch the documentary 'Food, Inc'. –  J. Musser Feb 16 '12 at 2:43
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@Shpigford: reasons to avoid roundup might include a half-life of several months and exaggerated safety claims by Monsanto. –  bstpierre Feb 16 '12 at 22:06

Further to the suggestion of goats, I had a large patch of Spiderwort (Tradescantia fluminensis) which was taken care of by two young hens within a couple of weeks.

You could try the chicken tractor method or just let them roam around.

There are many benefits to this method:

  • Free chicken feed
  • Free eggs
  • Improved soil
  • Chickens will do a good job of getting not just the tops of the plants, but they will scratch up the roots

With the Spiderwort the chickens were quite interested in eating it and it has hardly come back at all this warm season (in Australia) leaving a few small plants which I could easily remove by hand.

The only thing I would mention is to do some research to make sure the weed you have there is not toxic to animals.

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Re RoundUp - don't use Round up, if you must use a weedkiller, buy glyphosate. This is the active ingredient in Round Up, minus all the other additives they put in it which make it more of a threat to the environment. Glyphosate works just as well - if you want to add a surfactant, a squirt of washing up liquid will do the job. Note that Round Up once contained the slogan 'bio degradable, environmentally friendly'. This labelling was removed some while back when these claims were proved to be false. Black plastic or tarpaulins, if you want to go that route, must be anchored tightly to the ground to exclude, air, sunlight, and water, and should be left in place for a year to achieve good results. You could cover most of the area with those, and then use the most eco friendly solution of all - digging, with a fork, extracting all the roots, a patch at a time, just whatever you can handle.

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Any organic gardener will tell you Round Up damages the ground. It will cause resulting weed problems that last for years. It's also not organic.

A rototiller won't be of any help. It's better not to disturb the ground. Once the weeds are killed some other way a rototiller will just stir things up. If you use a rototiller when you still have weeds, it will just break them into tiny pieces that will regrow and make a mess.

A weed burner won't kill established weeds.

This is a reasonable area to use black plastic on. I suggest not thinking about it as an area you will transform overnight, but rather over a few years. You could think about covering a quarter of it at a time, then you don't need to buy so much plastic. The best plastic to use is woven landscape plastic, that will let through water and air. Unwoven plastic will kill all life in the ground, and it will take time to recover from this. Also unwoven plastic will stick and become a mess if you leave it too long. Black plastic takes about 6 months to completely kill weeds, not just a few weeks like someone said above.

A nice, organic and renewable way to kill the weeds is with wood chips or bark. You'll need a lot, it'll have to be delivered by truck. It'll be a little pricey. You'll need about 80 yards. You'll want an initial layer about 6 inches or thicker. As it kills the weeds it'll rot, feed the ground and get thinner. You can rake holes in it to put plants, or move it from one side of the yard to the other to maintain thickness. After about 2 years it'll mostly be gone, and you'll be left with rich weed free ground. When you get tired of the bark, you can rake it into a compost pile.

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I had a backyard that was all weeds. Before I was educated on weed killers ( 10 yrs ago)I sprayed the yard. It killed everything. The weeds came. Back after a couple of weeks before I had a chance to do anything. I did it again. The weeds didn't resurface. I didn't till ( this would bring more seeds to the top) I users dethatcher and removed everything. I put sod down and haven't had a problem with the weeds.

Round up is only active when absorbed by the plant. Once it hits the dirt it becomes inactive. You might try the tarps. Then lwhatever germinate use the round up as soon as you see the sprouts. I beleave in laying sod. See if your area has a master gardener program and call them shouts the round up.

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Roundup is active in the ground. It effects the micro-biota that makes soil rich. –  Jan Steinman Jul 9 '12 at 18:23

I would suggest Avenger weed killer. It's an organic (citrus oil) post-emergent herbicide. It works pretty well mixed at strongest ratio the day before and then sprayed on a hot day right before the sun hits the area. It is very fast and effective, with results two hours later. I have used it for clients for blackberries and it turns them brown in 2 hours. It does not work well on cape ivy. I think it's best in sunny locations.

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I suspect this product is only available to gardeners located in the Continental United States. –  kevinsky Jun 10 '13 at 19:07

A good non toxic herbicide is Round-up. Although it is not strictly organic, it is non toxic. It is systemic and works in less than 7 days usually. The refuse can be tilled in with no damage to new plantings. You will need to rototill or York rake the area before replanting grass.

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Since roundup is "Isopropylamine salt of glyphosate" It technically is Organic. However, it's probably not natural. –  Chris Cudmore Mar 9 '11 at 17:48
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Organic! Hardly. Round-up is a deadly herbicide/pesticide that is polluting the world. Please stop using it and buying into Monsanto's propaganda. See organicconsumers.org/monsanto/roundup080805.cfm –  user2843 Jun 4 '11 at 14:35
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Organic refers to compounds containing carbon. More directly, it is an IsoPropyl alcohol with an attached ammonia. Definitely organic chemistry. Which reminds me of the dry cleaner near me who advertises "100% organic solvents used." Technically, he is correct. But to quote Inigo Montoya: "You keep using that word. I do not think it means what you think it means." –  Chris Cudmore Feb 15 '12 at 18:21
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"Organic" is a term-of-art in numerous fields, with specific meaning in each. For food, "organic" is rather precisely defined as to exclude RoundUp and other herbicides. An "organic sculptor" would be puzzled by your assertion. A lawyer would start thumbing through his pages for some new meaning of "organic law." What you have said applies only to organic chemistry. –  Jan Steinman Jul 9 '12 at 18:23

Newspaper works also: put down some newspaper, spread mulch on top, wait a bit and rototill it all in.

Newspaper ink is soy based now so it's fine; prepare the soil and plant.

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