# Best Weed Killer
**URL:** https://boards.straightdope.com/t/best-weed-killer/982284
**Category:** In My Humble Opinion
**Created:** [April 7, 2023, 1:39am UTC](https://boards.straightdope.com/t/best-weed-killer/982284 "2023-04-07T01:39:26Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)
#### Post date: [April 7, 2023, 1:39am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/1 "2023-04-07T01:39:26Z")
If this is the wrong forum, mods feel free to move it.
What is the best weed killer? I’m not talking a weed & feed for my lawn or RoundUp for spot weed killing. I mean something I can spread to salt the ground so nothing can ever grow again.
Is there something like that?
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### Author:  [@wolfpup](https://boards.straightdope.com/u/wolfpup)
#### Post date: [April 7, 2023, 1:55am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/2 "2023-04-07T01:55:25Z")
Roundup will certainly do the job, although its effect will not be permanent (and neither will anything else, in the long run). It’s a broad-spectrum herbicide.
Aside from personal and environmental commentary that is not appropriate for FQ, I will say that I used it once – and only once – to good advantage in my desperate battle with some sort of invasive bush that kept growing to huge heights even when chainsawed down to a bare stump. It just sprouted again. I paid a gardener twice to cut the damn thing down with a chainsaw and haul away the debris – which completely filled the bed of his pickup truck each time. And then it started sprouting yet again. Completely fed up, I bought the herbicide glyphosate (Roundup – which is restricted here but legally available) and doused the stump with its yet-again newly emerging sprouts. It seemed to kill it, but it revived itself a few months later. I doused it again, and this time I think it’s done for good. Eventually I’ll either grind down the stump or have it pulled out.
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### Author:  [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)
#### Post date: [April 7, 2023, 2:00am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/3 "2023-04-07T02:00:14Z")
You said it yourself. Probably salt.
Most herbicides break down and none are likely to be fully effective against all plants for extended periods. Most are intended to kill living plants without long term implications.
Salt will leach down over time, but the dynamics of salt in soil is complicated.
Long term prevention of stuff growing is perhaps better addressed with things like fine mesh mats.
Glyphosate aka Roundup only works on a limited range of plants and needs them to be growing vigorously. It is great for most grasses, but barely touches many plants.
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### Author:  [@wguy123](https://boards.straightdope.com/u/wguy123)
#### Post date: [April 7, 2023, 2:12am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/4 "2023-04-07T02:12:36Z")
Weed mat will do it or do like they did in the old days and spread your used motor oil and turn your property into a mini superfund site.
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### Author:  [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)
#### Post date: [April 7, 2023, 2:15am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/5 "2023-04-07T02:15:28Z")
> [@wguy123](#):
>
> Weed mat will do it
All they do is make it impossible to pull out the weeds that grow through it.
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### Author:  [@DCnDC](https://boards.straightdope.com/u/DCnDC)
#### Post date: [April 7, 2023, 2:26am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/6 "2023-04-07T02:26:29Z")
What are you trying to kill? What is the ultimate goal? How large an area are attempting to clear?
Having dumped hundreds of pounds of salt on my own lawn trying to permanently kill the whole thing, I can tell you the main problem with that plan is quantity. You don’t just need a sprinkling, you need like a 2" thick layer. Seriously. That sounds like way overkill but trust me, it’s not.
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### Author:  [@thorny\_locust](https://boards.straightdope.com/u/thorny_locust)
#### Post date: [April 7, 2023, 2:44am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/7 "2023-04-07T02:44:51Z")
> [@Francis\_Vaughan](#):
>
> Probably salt.
> [@wguy123](#):
>
> spread your used motor oil and turn your property into a mini superfund site.
And probably your neighbors’, and the water table. Similar issues with that much salt. Somebody may sue you – an affected individual, or the municipality or water district. Or even your state.
You want the place bare for an extended time that badly, pave it. Solid, not something with cracks. But check your locality’s zoning regulations first; they may have an impervious-surfaces limit by now.
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### Author:  [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)
#### Post date: [April 7, 2023, 3:37am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/8 "2023-04-07T03:37:45Z")
[ ](https://morbotron.com/meme/S02E07/367623.jpg?b64lines=IFRoZSBwbGFuIGlzLAogYmFzaWNhbGx5LCB0byBwYXZlCiBvdmVyIHRoZSBhcmVhIGFuZCBnZXQKIG9uIHdpdGggb3VyIGxpdmVzLg==)
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 7, 2023, 5:13am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/9 "2023-04-07T05:13:56Z")
I remember someone who grew up in the “future’s so bright I gotta wear shades” 1950’s, told me about a neighbour who worked for a chemical company. He was touting something like Roundup or agent orange or whatever - the idea was to spray the entire lawn with it, kill everything, then spread fresh grass seed and fertilizer a week later, and ta-da = only the wonderful new grass, nothing else.
Kind of reminds me of the story of the medieval bishop in the Albegnesian crusade…
“How will we know who are heretic and who are proper Chirstians?”
“Kill them all and let God sort them out.”
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### Author:  [@wguy123](https://boards.straightdope.com/u/wguy123)
#### Post date: [April 7, 2023, 11:23am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/10 "2023-04-07T11:23:47Z")
> [@thorny\_locust](#):
>
> And probably your neighbors’, and the water table. Similar issues with that much salt. Somebody may sue you – an affected individual, or the municipality or water district. Or even your state.
I hope you don’t think I was recommending this when I gave it a “superfund site” classification.
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### Author:  [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)
#### Post date: [April 7, 2023, 11:47am UTC](https://boards.straightdope.com/t/best-weed-killer/982284/11 "2023-04-07T11:47:58Z")
Concrete
This will last until you get a little crack, then a dandelion will grow there.
You can cover the land with something like cardboard but it eventually breaks down and has to be refreshed.
Thankfully there’s no chemical that lasts forever and kills all plants that we are allowed to buy and spread on the ground.
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### Author:  [@FluffyBob](https://boards.straightdope.com/u/FluffyBob)
#### Post date: [April 7, 2023, 12:11pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/12 "2023-04-07T12:11:28Z")
Entropy always wins.
A really thick layer of mulch / washed rock works pretty good, but you need a lot. Minimum 6", more the better. Eventually detritus and decomposition will create enough humus for things to grow in again, and the whole bed will need to be raked up and refreshed. Any significant size and a skid steer and operator will be a must. Landscape mesh helps at first but greatly increases the labour and hassle when it is time to refresh things.
Concrete or road crush and plenty of regular traffic work alright.
I take it just letting things be wild is not an option.
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### Author:  [@thorny\_locust](https://boards.straightdope.com/u/thorny_locust)
#### Post date: [April 7, 2023, 12:36pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/13 "2023-04-07T12:36:35Z")
> [@wguy123](#):
>
> hope you don’t think I was recommending this when I gave it a “superfund site” classification
No, I didn’t! I was taking off from that “superfund” description.
Sorry to have been unclear.
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### Author:  [@solost](https://boards.straightdope.com/u/solost)
#### Post date: [April 7, 2023, 12:38pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/14 "2023-04-07T12:38:12Z")
We have a very long gravel drive that opens into a small parking lot-sized area, so we’ve been fighting weeds that grow up through the gravel for years. We used to use Roundup, but due to the cost and the rumors of it being a carcinogen (which I guess is overblown…or not? Who knows), Mrs. solost found a homebrew solution: a mix of white vinegar, salt, and dish detergent. We mix it up, put it in a sprayer, and use it just like Roundup, and it works about as well if not better. It’s a ‘once a month’ thing though, it’s far from permanent. The phrase ‘growing like a weed’ exists for a reason. I’ll ask her for the exact formula if you’re interested.
There are also preemergent herbicides, which stop seeds from germinating but do not harm established plants. I’ve never used these, so I can’t attest to their effectiveness, but I’ve found the idea of them intriguing:
> **[Preemergent herbicide](https://en.wikipedia.org/wiki/Preemergent_herbicide)**
>
> Preemergent herbicides are a form of chemical weed control which prevent germinated weed seedlings from becoming established.
> In some areas of the world, they are used to prevent crabgrass from appearing in lawns.
> Preemergent herbicides are applied to lawns in the spring and fall, to prevent the germination of weed seeds. They will not affect any established plant. In the spring, they should be applied when air temperatures reach 65–70 °F for four consecutive days. In the fall, they should b...
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### Author:  [@burpo\_the\_wonder\_mutt](https://boards.straightdope.com/u/burpo_the_wonder_mutt)
#### Post date: [April 7, 2023, 1:18pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/15 "2023-04-07T13:18:55Z")
**Best Weed Killer**?
Well, that would have to be our own @kayaker. I understand he can kill off a quart Ziploc bag in about 14 minutes. YMMV.
🤣 😉
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### Author:  [@kayaker](https://boards.straightdope.com/u/kayaker)
#### Post date: [April 7, 2023, 1:21pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/16 "2023-04-07T13:21:43Z")
👍. I am sitting at work, laughing.
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### Author:  [@burpo\_the\_wonder\_mutt](https://boards.straightdope.com/u/burpo_the_wonder_mutt)
#### Post date: [April 7, 2023, 1:23pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/17 "2023-04-07T13:23:10Z")
You’re a good sport.
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### Author:  [@bump](https://boards.straightdope.com/u/bump)
#### Post date: [April 7, 2023, 1:57pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/18 "2023-04-07T13:57:59Z")
Seems like some of the herbicides that are labeled for weed control and NOT for food are somewhat persistent, and are intended to be sprayed on things like rock paths and the like to keep the weeds down longer than regular glyphosate would.
Here’s an example:
[Ortho Groundclear Year Long Vegetation Killer1 | Ortho](https://ortho.com/en-us/shop/weeds/ortho-groundclear-year-long-vegetation-killer1/ortho-groundclear-year-long-vegetation-killer-one.html)
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### Author:  [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)
#### Post date: [April 7, 2023, 2:23pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/19 "2023-04-07T14:23:48Z")
> [@DCnDC](#):
>
> How large an area are attempting to clear?
That’s the big question. A small plot is easy, a large lawn is difficult.
Weed mat/barrier/fabric works well but needs to be installed properly and maintained. I’ve also used discarded shower curtains to kill off remaining plants after turning over soil for a garden plot.
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### Author:  [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)
#### Post date: [April 7, 2023, 2:31pm UTC](https://boards.straightdope.com/t/best-weed-killer/982284/20 "2023-04-07T14:31:22Z")
I’d be apprehensive about using an herbicide so powerful that a single application would effectively prevent plant growth forever. Never heard of such a thing anyway.
If the objective is Permanent Weed-Free Living, an impermeable physical barrier (not “weedblock” fabric) is the best bet. If a garden space is involved, close planting, a good layer of mulch and periodic attention works fine.
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