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I was reading over here that salt can be used to control weeds in paved areas?

  1. Is salt an effective way to kill all (or most) plant types?
  2. Is it permanent?
  3. Will using salt effect ground water (I have a bore) and nearby gardens?
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Yes, it's effective. No, it's not permanent because water dissolves it and leaches it into the drainage, some of which ends up in your water table. And it really plays hell on concrete, causing spalling and crumbling. –  Fiasco Labs May 24 '13 at 0:50
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2 Answers

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Yes, salt will kill plants. In theory, if you use enough of it in the soil, it will kill a tree.

Regarding whether its permanent, no, its not. If you saturate open ground with salt, everything dies, and, by and large, nothing grows for some months, even years. In your case, you want to know whether it works permanently when its been applied to paving. No, is the answer, it will wash through eventually, so you will need to re apply.

Yes, using lots of salt to kill weeds will affect ground water, although how much its affected depends entirely on how much you use and how often. A small amount occasionally is unlikely to cause much harm.

But there is one other factor to consider - salt damages concrete and other paving materials. Damage occurs from the use of salt/grit mixes on concrete or paved surfaces as a de-icing solution - it's more likely to occur when used neat on paving, even if you're trying to only get it in the cracks. It is toxic to plants and other forms of life within the soil, and the risk of run off onto planted areas when it rains should also be considered.

Personally, I would not recommend it. The use of salt as a weedkiller because it's believed to be 'organic' and less toxic than a commercially available tailored-for-purpose path weedkiller is erroneous - salt, used frequently, is much more toxic in comparison to one or two applications of path herbicide a year, assuming the herbicide is intended for amateur garden use rather than professional agriculture.

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Salt can damage cements and the concrete itself, but it is a real killer when it comes to reinforced concrete as it greatly accelerates the rebar corrosion. Iron expands as it rusts causing the concrete to crack - hence the cracks in old road bridges. "Concrete Cancer" is a name sometimes given to the effect. –  winwaed Sep 17 '12 at 13:34
    
I'm thinking of using it on a bricked area and have zero experience using salt to de-ice. How will it damage the bricks? –  Coomie Sep 18 '12 at 3:48
    
Salt will pit the surface, eventually causing spalling to occur. –  Bamboo Sep 18 '12 at 12:33
    
In my opinion bricks are probably better than most surfaces, but I still would NOT do it for the other reasons @bamboo describes. –  winwaed Sep 18 '12 at 13:02
    
Agree with winwaed, particularly if you want to be a natural, organic gardener. Salt's worse than pesticide. –  Bamboo Sep 18 '12 at 13:48
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I have been using salt to control my neighbor's bamboo for 5 years now. He planted a 200 foot line of bamboo with no intention of controlling it. I had to trench my own yard for 200+ feet and lay in a barrier 3 feet off the property line. (After I removed over 100 feet of roots destroying my yard). Then to keep the plants from filling in from the barrier to the property line I place 800-1000 pounds of salt once to twice a year along the area. Any bamboo that crosses the property line not only stops but it kills the offending plants. Thankfully after 5 years of doing this, the bamboo is more intent to grow towards his pool and house instead of filling up my yard.

The reason I went with salt is because other toxins are too expensive, dangerous to kids and I cannot legally spray any of his plants. This leaves me with constant vigilance for new plants which takes much of my time and doesn't cure the problem or creating the "no plants land" 3 feet wide by 200 feet long and salting it. Any offending plant ends up committing suicide and I never touch his property or plants.

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