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

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?)

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.

Tips:

- 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.