(Blue-)Green Weed Spray - From Household Ingredients.




About: I love to design and make things; and am currently developing a variety of small consumer products.

UPDATE- 2017: I've tried to delete this instructable several times, but since "it has been entered in at least one contest" (8 years ago!!), it can't be deleted. Rather than spend another 15 minutes trying to find a way to communicate with the Instructables staff, I'm simply editing this post to omit the salt from the recipe.

This stuff is cheap*, effective, and works fast. It could be the new Roundup [™] but without the cancer-causing ingredients, though it does not necessarily kill the roots of a weed. I find it is just as effective as the high priced brand.

N.B., I have adjusted this recipe, omitting the salt, which is not good for soil where you want plants to grow.

My yard is "organic", meaning I avoid using petroleum-based pesticides and herbicides and other toxic stuff.

I don't like pulling weeds out of cracks in the pavement, be it those lousy pink pavers, or the antique concrete driveway. (It used to have a strip of grass down the middle. I'd like it better if it still did!)

My brothers are big fans of Roundup, which has recently been found to cause cancer (as has been suspected for a long time), etc. A horticulture expert I know says that it breaks down over time, (my brother's justification for using it), but nobody knows exactly what it breaks down into!

A little web searching turned up various recipes. This is my variation. See the before and after photos below.

  • (I'm told that Roundup is cheaper by the gallon, but at what cost to the environment?)

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Step 1: Rob the Kitchen...

Chances are you have most of this stuff in your kitchen already.
If you don't have a gallon of white vinegar, most grocery stores carry it; even the Dollar, 99 cent, etc. stores usually have it for, well, a dollar, a Euro, etc.

The shopping list:

- 1 gallon (about 3.8 litres) of white vinegar
- 2 Tablespoons of dishwashing liquid. The kind used for hand washing dishes. (Not the the kind you put in dish washing machines.)

- A sprayer, like the yellow one here. Or a smaller, trigger-pump bottle.

- A permanent marker, for labeling the brew.

Optional: About 2 ounces of rubbing alcohol. (not shown)

Step 2: Mixing It Up

I recommend you do the mixing outside, not in the house.
This tip alone could save you from banishment, going to bed without your dinner, or worse!

- I like to put the soap and other ingredients into the vinegar bottle, which makes it blend more easily because the detergent doesn't stick to the sides of the bottle. If you have a pump sprayer with a wide mouth, you can put all ingredients directly into the sprayer.

I used a plastic container as a funnel, pinching the sides to make it fit the top of the vinegar bottle.

- Then carefully add 2 Tablespoons (about 30 grams) of dishwashing liquid.

- Put the cap on tight, and shake well. If it's not a screw cap, keep your hand on it to avoid unfortunate incidents, and another trip to the store for vinegar.

Step 3: The Finished Product

You're already greener, because you've re-used the original vinegar bottle.

Be sure to label it clearly so no mistakes are made! You wouldn't want anyone adding this to their laundry, or serving it at breakfast. The ingredients are fairly innocuous, and it's still a good idea to keep the jug out of reach of children.

Step 4: Blast 'em!

Or rather, give 'em a light dousing. I use my pump sprayer, seen in Step One, pumped up just enough to put out a very low pressure spray. It's easy to control, and doesn't deliver too much at once.

All you need is enough to coat the surface of the weeds. The dish soap helps to dissolve the waxy coating on the outside of the leaf(different for each weed), the vinegar (and alcohol) dessicate the leaves, and you leave confident that when you see them the next day, they will be withered, and on their way out.


- For best results. spray on a warm, sunny day, when the Sun will be on the weeds you've just sprayed for at least a couple of hours. A hot day with several hours of Sun exposure is better.

- Remember that you are using a corrosive liquid. It did a fine job removing the oxidation from the brass wand on my sprayer, it can do harm if sprayed on any surface that is sensitive to acid. This may include concrete! [Chemists and other experts, please jump in here with some solid information.] I'm going to keep an eye on my driveway, and (not so) beloved pink pavers.

Update: closer inspection of the pavers and driveway reveal no apparent damage. But as with substance with damage-causing potential, use with care!

When in doubt, rinse!

Step 5: Results After 24-36 Hours.

As you can see, the weeds and grass have shriveled, and look dry. Given a few more sunny days, they will be brown, and can be rubbed away.

The smaller weeds won't grow back. The more determined ones may show up again, smaller and weaker. If you get them when they are small, instead of letting them get as big as the ones in my photos, your weed population will dwindle. Also, you won't be allowing new seeds to form, so next year you'll have fewer to contend with. Especially if your neighbors do their part!

I've noticed that the weeds I sprayed last year have not come back in the same places they've been occupying annually for many years. This year, it's mostly grass.

Like raising kids, they grow fast, and it pays to attend to them when they are small. This year, I got a late start, and just to see what happens, sprayed even the larger clumps of grass and weeds. As nice as spraying is for mass weed removal, sometimes it's faster and easier to just bend over and pull 'em. ;-)

Please comment (and vote!) and let me know how yours works out, and if you have any new recipe ingredients.
I'm a little curious to see if a mix partially diluted with water will work as well.

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    13 Discussions


    10 years ago on Introduction

    Nice instructable. I very much like to see this kind of thing. Be careful with Salt...it will also destroy most masonry (Concrete, bricks, mortar, etc) BTW, don't get carried away by everything being labeled carcinogens.....pure water is an amazing mutagen/carcinogen, an oxygen is among the most biotoxic chemicals. There is no such thing as "not natural" since we don't quite have the omnipresence to 'create' our own matter yet ;)

    3 replies

    Reply 1 year ago

    Water is by far the worst chemical on earth, it kills more people than any other cause on earth, except old age.


    Reply 10 years ago on Introduction

    odiekokee, I think you should go down in the record books for one of the best quotes ever! I've thought the same thing before about natural vs. unnatural, but you summed it up perfectly. People focus too much on all this 'green' bandwagon BS and fail to understand their world for what it really is. Thank you for your insight...


    Reply 10 years ago on Introduction

    Welcome :) "......said He to the scientist "You may think you can invent life from the inert elements, and so you may be able. Prove it I say." The scientist replied to Him "it is quite simple, I merely take these elements and invent life" "Ahh, yes, but you see," He said, "To invent it as 'your' life, you muts also invent 'your' elements first. From what will you invent these??" flame away ;)


    10 years ago on Introduction

    Disolved salt will kill weeds ,will also kill all plants , Table salt ,use 2ounces to a gallon.. Harmful to grass ,But on a driveway it would be fine. We used to do this in high school to spell out the HS name on competitors school yards, PS I think it's against the law now.........

    1 reply

    Reply 1 year ago

    Your comment depends on your plants, if you are in Florida, the grass can survive salt. Salt is not evil, it removes other heavy metals from water, I would like to see a study where the NaCL content precentage for XXX hours will kill something like Kentucky Bluegrass, let alone a generic crabgrass.


    10 years ago on Introduction

    I suspect that salt and vinegar are not used as commercial weedkillers because it will linger in the soil, leech and be a long-term hazard to any growing plants - which is not good if you want a nice garden

    2 replies

    Reply 1 year ago

    There are a lot of things that will kill plants, the last one I would use is salt, I have no issue with RoundUp, but always looking for alternatives. Salt would be the bottom of my list.


    Reply 10 years ago on Introduction

    No doubt. And petro-chemicals are probably cheaper. You may have noticed that I've only used my weed spray in cracks between concrete pieces, not in open areas. I think I'll try a salt-free version, and see how it works. I know that vinegar alone is not very effective.


    Reply 1 year ago

    if you hit the 20 - 25% acid concentration, it will kill everything, can't say it won't take 2 applications, but it works.


    Question 1 year ago on Step 5

    You don't mention your acid concentration, but I have only had good results with concentrations around 20% (http://boulder.extension.colostate.edu/natural-res... I can only find this concentration from the local asian markets, and is way too expensive to use. I would guess I can make my own acid buying a solid, and making my own solution.

    As an instruct-able goes, why are you including soap? This will have zero effect on the plants, as I use a few drops in a spray bottle to take care of bugs (it suffocates them, doesn't kill them directly).


    7 years ago on Introduction

    Don't forget to consider the bees. Any pesticide is VERY destructive to them!