Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: cheryl j on 11/05/2012 03:56:12
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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?
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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.
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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.
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"What non toxic substance can i use to kill..."
None.
Non toxic things don't kill things ( by the definition of toxic)
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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?
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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.
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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.
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Boiling water?
or skip the boiling stage, and go for extreme prejudice http://www.groworganic.com/weed-pest-control/organic-weed-control/weed-torch.html (http://www.groworganic.com/weed-pest-control/organic-weed-control/weed-torch.html)
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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.
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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.
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You could also over-fertilise in the gaps; several times the normal recommended amounts.
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Sodium chlorate is used as a weedkiller ...
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.
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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?
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How about urine?
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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.)
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Dog urine
I doubt even this dog (http://www.youtube.com/watch?v=KH7viWp5KrE#t=1m20s) could be trained to only pee on weeds in the gaps in paving. [:)]
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Dog urine
I doubt even this dog (http://www.youtube.com/watch?v=KH7viWp5KrE#t=1m20s) 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.
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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.
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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.
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Dog urine
I doubt even this dog (http://www.youtube.com/watch?v=KH7viWp5KrE#t=1m20s) 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]
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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.
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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
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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.
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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.
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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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I suppose one of the risks of road salt usage is that if there is semi-arid land downstream of the area that applies the roadsalt, that uses the river water for irrigation, then it puts those farmers at risk.
Not all states use Road Salt. Oregon does not.
http://www.subaruforester.org/vbulletin/f76/map-states-use-road-salt-27855/
I believe that Washington does use it in the Puget Sound area, but at least that salt only travels a short distance to reach the Pacific Ocean. Other areas in the country have a much longer downstream impact.
I consider the salt to be extremely destructive, and would hope highway officials would pursue alternatives. A non corrosive liquid de-icer is often used here in Oregon.
I also have refused to use salt de-icers for sidewalks.
I was surprised to see on the map that California is listed as using road salt. If the salt is a problem for the agriculture there, I would think they would prohibit the use of road salt, as well as working with all the upstream states, Nevada, Utah, and New Mexico to find alternatives. (most of Idaho's drainage is northward and their application is listed as minimal).
Apparently Australia has been developing salt tolerant wheat varieties. Perhaps the salt will become a natural herbicide.
http://www.sciencedaily.com/releases/2010/04/100423094622.htm
http://www.sciencedaily.com/releases/2012/03/120311150717.htm
Anyway, compared to the approximately 10 million tons of salt used on the roads in the USA each year, a couple of pounds of salt used along a walkway would be pretty insignificant. However, I wouldn't consider it an optimal solution.
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The question has been around for a while.
http://en.wikipedia.org/wiki/Paracelsus#Contributions_to_toxicology
and I don't think they have solved it yet.
This
http://echa.europa.eu/documents/10162/13632/information_requirements_r8_en.pdf
talks about threshold and non threshold effects.
The issue is even more complicated with things like salt, copper iron or even oxygen where too much is bad for you but not enough is also bad news.
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There are a number of dose related values that you may see.
LD50 is the Lethal Dose in which 50% of the sample group dies.
http://en.wikipedia.org/wiki/Median_lethal_dose
But, as BC mentioned, it can be complicated. For example, some toxins build up in the body, or otherwise are more represented by a cumulative dose.
There is also a concept of Hormesis, in which low doses of a normally toxic substance may in fact be beneficial.
http://en.wikipedia.org/wiki/Hormesis
Radiation exposure, for example, is something that some people consider any dose as being a risk, but in fact there is an amount of hormesis effect, so low dose radiation may in fact reduce the cancer risk.
http://en.wikipedia.org/wiki/Radiation_hormesis
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It's a long way from clear that hormesis is real.
As that wiki page says "Quoting results from a literature database research, the Académie des Sciences — Académie nationale de Médecine (French Academy of Sciences — National Academy of Medicine) stated in their 2005 report concerning the effects of low-level radiation that many laboratory studies have observed radiation hormesis.[6][7] However, they cautioned that it is not yet known if radiation hormesis occurs outside the laboratory, or in humans. 8 "
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If it's a small area, cover it with sheets of black plastic, which should get rid of every kind of plant. Non-toxic, reusable, etc.
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I have heard that biodiesel will kill grass and weeds for about a year or so after a spill, then they will come back quite well.
You can mulch your flowerbeds with bark. Perhaps using a landscape fabric below the bark. The landscape fabric is supposed to be more porous than black plastic, and doesn't float up as badly.
I dump my grass clippings around my flowerbeds which will also help control the weeds. Then the clippings go away over the winter.