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Author Topic: What non-toxic chemicals may be used to kill unwanted grass?  (Read 16465 times)

Offline cheryl j

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What non toxic substance can i use to kill grass in in the cracks in my side walk or along my rock border in my garden. Would salt work, or an acid or base?
« Last Edit: 24/05/2012 22:17:56 by chris »


 

Offline Don_1

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Re: killing grass
« Reply #1 on: 11/05/2012 15:07:29 »
Whatever you use it will only be temporary. Grasses are pretty resilient and even if you kill off the top growth and the root, the chances are seed will still be there ready to germinate as soon as it gets the chance. If not grass re-growing, it may be some deep rooted wild plant (weed) such as Hawksbeard or Dandelion.

Your best bet is to pull up the grass and plant something which will prevent its regrowth. such as Camomile, Thyme or a Sedum. Beware of some ground cover plants which can spread like wildfire and be a real pain to get rid of. Thyme can be a bit of a pain as can Mind Your Own Business. In cracks, let mosses grow.

Otherwise, I'm affraid its a case of perseverance and a pain in the back! Even if you resort to weed killers, they will only last for a limited period, which will depend mostly on rainfall.
 

Offline CliffordK

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Re: killing grass
« Reply #2 on: 11/05/2012 22:58:29 »
There are, of course, rubber sealants that you can put into the sidewalk cracks, although not as effective around garden stonework.  If you haven't gotten all the grass killed off, it can be pretty resilient and push the rubber out of the way though.
 

Offline Bored chemist

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Re: killing grass
« Reply #3 on: 12/05/2012 01:03:34 »
"What non toxic substance can i use to kill..."
None.
Non toxic things don't kill things ( by the definition of toxic)
 

Offline cheryl j

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Re: killing grass
« Reply #4 on: 12/05/2012 01:42:07 »
Well what i meant by nontoxic was not a herbicide like Round up, or various weed killers. I was thinking that something with a high or low ph or salt might kill the plant it landed on, but would eventually be diluted or neutralized as it spread out, and also not possibly carcinogenic. I don't really care if its short term since I'm in Canada and its only warm for about 2 months anyway. But I hate spending those two months weeding. How environmentally bad would chlorine bleach be?
« Last Edit: 12/05/2012 01:43:48 by cheryl j »
 

Offline Geezer

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Re: killing grass
« Reply #5 on: 12/05/2012 07:07:15 »
Get a goat. Goats eat anything. There are goat herders around here who rent their goats out to the highway departments to control the noxious weeds at the sides of the roads.
 

Offline Bored chemist

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Re: killing grass
« Reply #6 on: 12/05/2012 17:31:32 »
Boiling water?
It depends how big an area you are treating.
Any acid, base or salt that's toxic enough to kill the weeds will probably cause at least some damage when it's washed into the flower beds.
Bleach is converted to salt and that's bad for the plants.
 

Offline Geezer

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Re: killing grass
« Reply #7 on: 12/05/2012 18:26:59 »
 

Offline wolfekeeper

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Re: killing grass
« Reply #8 on: 12/05/2012 20:41:26 »
One time i had a chrome plated bumper on a car that was parked for a long while. The moss all died underneath the bumper where the water had run off.

Dunno whether copper metal would work. A lot of copper salts are quite toxic. That would gradually give off poisons where you put it, hopefully without being dreadfully toxic; low levels of copper are nutrients, high levels, not so much.
 

Offline Geezer

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Re: killing grass
« Reply #9 on: 12/05/2012 20:47:18 »
Copper is certainly toxic to moss. You can prevent moss from growing on roofs by nailing a copper strip along the ridge. Not sure what it does to grass though.
 

Offline wolfekeeper

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Re: killing grass
« Reply #10 on: 12/05/2012 21:03:22 »
You could also over-fertilise in the gaps; several times the normal recommended amounts.
 

Offline RD

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Re: killing grass
« Reply #11 on: 12/05/2012 23:24:05 »
Sodium chlorate is used as a weedkiller ...

Quote
Most commercially available chlorate weedkillers contain approximately 53% sodium chlorate
http://en.wikipedia.org/wiki/Sodium_chlorate

but apparently has been banned in the EU since I last used it.
 

Offline Bored chemist

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Re: killing grass
« Reply #12 on: 13/05/2012 15:19:25 »
There's a fundamental issue with this thread.
Historically, society asked the chemists if they could come up with replacements for old fashioned weed killers like salt or acid because they were not very safe or environmentally friendly- they tended to accumulate in the soil (and people got tired of pulling weeds by hand).
The researchers came up with things like glyphosate.
It has low mammalian toxicity (oral LD50 in rats is > 5 grams/kg. Salt, by comparison is about 3). It's not carcinogenic (unlike spraying acid- sulphuric acid spray is a known human carcinogen).
It's a weak teratogen in some species- but then, so is salt.

So the idea that you should replace roundup by something "non toxic" like salt or acid simply doesn't make sense.
Cheryl- the world of science already answered the question once. But it seems you don't want to listen to the answer.

Why is that?
 

Offline CliffordK

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Re: killing grass
« Reply #13 on: 13/05/2012 21:46:24 »
How about urine?
 

Offline Geezer

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Re: killing grass
« Reply #14 on: 13/05/2012 21:50:39 »
How about urine?

Dog urine certainly does a number (1) on a lawn, although I think lady dogs are best (or worst, if it's your lawn.)
 

Offline RD

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Re: killing grass
« Reply #15 on: 13/05/2012 23:51:36 »
Dog urine

I doubt even this dog could be trained to only pee on weeds in the gaps in paving.  :)
« Last Edit: 13/05/2012 23:56:59 by RD »
 

Offline Don_1

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Re: killing grass
« Reply #16 on: 14/05/2012 13:47:07 »
Dog urine

I doubt even this dog could be trained to only pee on weeds in the gaps in paving.  :)

I can't stand 'talent shows' and animal acts are usually real naf, but the wife called me in to see this one.

Quite remarkable.
 

Offline Don_1

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Re: killing grass
« Reply #17 on: 14/05/2012 13:58:39 »
The grass growing in these areas will probably be Ryegrass. It is widely used in garden lawns and where toughness and resilience are required, such as sport grounds.

It is even used in quality lawns to add reslience to the more fine grasses such as the fescues and bents.

It is tough and persistant.
 

Offline Bored chemist

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Re: killing grass
« Reply #18 on: 14/05/2012 19:38:07 »
They train racing greyhounds to pee in sample cups for drugs testing.
I vaguely wonder if the first person to think  " We could get the dogs to pee in sample cups" was tested for drugs.
 

Offline CliffordK

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Re: killing grass
« Reply #19 on: 15/05/2012 04:15:47 »
Dog urine
I doubt even this dog could be trained to only pee on weeds in the gaps in paving.  :)
I can't stand 'talent shows' and animal acts are usually real naf, but the wife called me in to see this one.
Quite remarkable.
Very cute.
I saw all 3 shorts of the Ashleigh and Pudsey shows.  I liked the second one (above) best.  Perhaps someone said a dog show had to have a dog walking up a ramp and through a tunnel, but I think it was all about the dance. 
Glad to hear she won the show.
Hopefully she has some good investment advice for the winnings, and potential future TV commercial spots. 

Dogs, of course, aren't the only source for urine.

You do have a tall fence around the back yard...  don't you?   :o
 

Offline cheryl j

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Re: killing grass
« Reply #20 on: 23/05/2012 01:45:03 »


So the idea that you should replace roundup by something "non toxic" like salt or acid simply doesn't make sense.
Cheryl- the world of science already answered the question once. But it seems you don't want to listen to the answer.

Why is that?

I'm actually not someone who assumes that something "natural" is always less toxic or less likely to be carcinogenic than compounds that are created or modified in a lab. Tobacco after all is natural. So I would take almost any suggestion. My assumption was based on the physiological concept that certain compounds like salt are harmful in large amounts, but even necessary for life in small amounts, which is why salting fish prevents bacterial growth but doesnt really harm us when we eat it.  The corrosiveness of acid is also a matter of degree, although as you said acids can have other chemical properties aside from their effect on pH.

I am right next to a river, and had heard that round up affected amphibians.
 

Offline Bored chemist

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Re: killing grass
« Reply #21 on: 23/05/2012 22:14:08 »
If you use salt, for example, it will build up in the soil and, unless the plants you want happen to be salt tolerant then you won't grow much.
There is an alternative scenario. the salt might get washed into the river.
If it's diluted enough then it won't have any effect.
Of course, the same would be true of roundup- except that it is destroyed in the soil by bacteria so less of it will get to the river.

That's the point- glyphosate has a "self destruct" mechanism: salt or acid don't
 

Offline CliffordK

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Re: killing grass
« Reply #22 on: 24/05/2012 00:02:23 »
Depending on where you are, the governments will salt the roads, usually a lot more than you could possibly put on your garden, so I wouldn't worry about the effect of a little salt on your garden or walkways would have on the rivers.  When I was in St. Louis, there were days when I would wake up in the morning to see the roads blanketed in white...  and not a snowflake to be seen anywhere!  One could smell the salt dust as one would drive, just about like being at an inland ocean.

When salt enters a river, the salt dilutes well, then gets flushed down to the ocean quickly (assuming the river drains to the ocean).

There are issues in some areas where irrigation will raise the natural salt level in dry lake beds, and poison the soil.  In most other areas, it would take an awful lot of salt to do long-term poisoning of the soil with salt.  How long do you expect your walkway to last?  Is it permanent?  There will be a small plume of salt going away from where you deposit it, but it should not be too bad.
 

Offline Bored chemist

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Re: killing grass
« Reply #23 on: 24/05/2012 19:04:13 »
I'm told that in some areas of Derbyshire there are seaside plants growing alongside the roads because of the salt pollution.

What do you mean by "the salt dilutes well". Does it get diluted any better than glyphosate?

Salt builds up to harmful levels, even where it is not added deliberately.
http://westernfarmpress.com/management/salt-build-adds-water-crisis
Of course, it's less of a problem if you have a river you can pollute.
 

Offline cheryl j

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This a tangent, but something I've always wondered about, but I'm not sure how to word my question.  How does one differentiate between chemicals whose anti-biological properties are clearly related to concentration. Like salt for example. We actually need a certain concentration in our blood to create the right osmotic environment for our cells. But of course, too much, like being on boat in the ocean and attempting to drink salt water, would kill us. Is this the same or different from "safe" levels of chemicals, like say, lead or mercury, which in miniscule amounts probably doesn't cause measurable harm, but some how never really seems like a good thing.
 

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