Sunday, April 28, 2013

SMACKDOWN: Vinegar vs Glyphosate for Weed Killing

Various blends of vinegar, salt and dishwashing liquid being used as an "organic" or "natural" or "no chemicals" weed killer are all over Pinterest and gardening blogs. They claim it's faster, cheaper and better than "Roundup" herbicide.

I have no clue how a blend of a commercially produced acid and a concentrated household detergent could be considered either "natural" or 'chemical-free". But I'm all for cheaper and better, so I tried it. I did a comparison test in early March by spraying two clumps of my worst weed, annual blue grass.
One side is vinegar, salt and dishwashing liquid
the other is Glyphosate.
You guess which is which.

The Commercial Herbicide

If I use herbicides, I use glyphosate, the generic herbicide version, not whatever blend is currently being sold as trademarked "Roundup"*.

Glyphosate has close to a 100% kill rate with one application if you follow the directions. It's a slow herbicide, but it's fast enough that if I spray on a weekend I can see what I missed the following weekend. The sprayed weeds are yellowing and wilting and the green ones are the ones I missed.

The Vinegar-based Recipes:

With lots of salt: "2 cups table salt, 1 gallon white vinegar (make sure it has 5 percent acidity)". Gads, the salt content alone could sterilize the dirt and prevent anything from growing. Have they not heard of salt damage? Carthage?

With some salt: "3 gallons for around $4.00 Worked better than Round Up killed the weeds/stray grass on first application. One gallon of vinegar, 1/2 c table salt, 1 tsp Dawn." This is the recipe I used, cut down to make a pint of the mix.

Without salt, and with a dislike for the ever-popular Dawn brand liquid detergent: "4 C. Apple Cider Vinegar, 1 t. Dish Soap (not Dawn) Mixed in a spray bottle. Add soap, then vinegar. Don't shake (BUBBLES) It all seems so gentle and harmless but remember, vinegar is acidic and not selective when sprayed on plants."

Is It Cheaper?

I can buy generic glyphosate concentrate at Walmart for under $8. Mixed with tap water at the recommended dilution, it makes 10 gallons of herbicide, so that's 80 cents a gallon for the commercial herbicide.

Vinegar - plain white generic vinegar with 5% acetic acid - is $1.89 to $2.12 a gallon at the local stores, so the vinegar mixes are 2 to 2 1/2 times more expensive than my generic glyphosate mix.

It's only cheaper if you compare the vinegar solution with buying ready-mixed containers of herbicide, which is not being thrifty. Convenient, but for the few minutes it takes to mix up a gallon of weed killer it's not worth the added cost.

Is it Better?

The vinegar spray looked impressive 3 days later. The clump was yellowing and turning brown at the tips. The glyphosate sprayed clump was still green. Unfortunately, I didn't take a closeup picture.

Ten days later I checked again. Uh-oh! The grass given the vinegar treatment had recovered, showing fresh green color. The glyphosate treated clump was yellowing as expected, with just a trace of green at the tips of the seed heads.
Glyphosate on the left, vinegar mix on the right, 10 days after spraying.
Three weeks later it was a clear win for the glyphosate. The vinegar treated clump was green and healthy, the glyphosate treated one was dead. 
Glyphosate, 3 weeks later

Vinegar mix, 3 weeks later

But, but … 

… say the fans of the vinegar mix .... you just have to keep treating the weeds and they will eventually die. That may be true, but if I have to spray the weeds several times with a solution that is twice as expensive as the glyphosate, tell me again how it's cheaper and better. Also, annual weeds die here when the weather gets hot. The purpose of killing them is to prevent their setting seeds and multiplying all over the yard.

* NOTE: “Roundup” used to be just glyphosate, but Monsanto has added some other herbicides to it to give it a faster “knockdown”. Apparently most of the gardening public wants to see weeds appear to shrivel and die by the next day.


Joe'sCentipede said...

The vinegar that actually kills plants is a 20% concentration. You're exactly right that the salt is probably doing most of the killing in that solution. Carthago delenda est! 20% vinegar can be dangerous to apply, so you want to wear protective gear, especially if it's windy. It's also not sold at every grocery store.

Joe'sCentipede said...

Oh, and while we're on the subject of acidity, at what rate did you apply sulfur and how deeply did you incorporate it into the soil? Do you have a caliche base under your topsoil?

Lazy Gardens said...

Joe - I know about the 20% horticultural vinegar. I was testing the widely publicized household vinegar mix to see if it worked or not. It didn't.

About the sulfur: I sprinkled it onto the dirt in a thin layer until about 50% of the surface was covered with the pellets. Then in the lawn area the sulfur got tilled in 6-8 inches deep. In a garden area I just rake it into the top couple of inches and put mulch on top. It doesn't make much of a difference in pH, but it does increase the availability of the iron and other minerals.

Yes we have caliche under some parts of the garden, although the plants are breaking through it and breaking it up.

The original tree plantings were reportedly done by hammering a hole into the caliche and dumping a gallon of pool acid into the hole. When it stopped fizzing, they hammered a crowbar down as far as it would go and dumped in more acid ... repeats until there was a drain hole.

Once the tree roots get into a crack in caliche they will break it into chunks and it's no longer a problem.

Joe'sCentipede said...

I figured you had run across it. Thanks for the quick responses!

I've just recently plugged in my Buffalo Grass (Prestige from Todd Valley). I'm in Las Vegas with caliche as well but I had read Buffalo Grass takes it in stride.

That tree hole digging sure would have been something to see!

margaret sales said...

I had to leave the home for some days..when i returned i saw weeds overgrown over my crops and pop up sprinklers.....I used vinegar over it and the next day all my crops seemed to be dried up....I think i had applied more than what was needed.....thanks for the information!!!

Anonymous said...

What type of glyphosate did you get at Walmart?

Lazy Gardens said...

Brand name is "Eliminator"

Reading the label, it's 41% glyphosate.

Kevin Talley said...

I bought "CropSmart" Glyphosate 41 plus, at Rural King, for under $18.00 per gallon about 33 years ago. It is $20 per gallon now. Most weeds need about 2 oz. per gallon of water. I'm in the shade and need it a little richer, but at 2 oz per gallon it computes to a bit over 31 cents per gallon.

Anonymous said...

Of course using GLYPHOSATE will be quicker and even cheaper but think about your health and that of your children and pets. Not everyone is diligent about wearing protective clothing and a mask while spraying.....this stuff is highly toxic people....cancer, Parkinson's disease, and other neurological problems have been linked to this and other toxic weed killers.....come on do yourself a favour they are just weeds!!!

Lazy Gardens said...

Dear Anonymous:

Glyphosate is not "highly toxic". It is not implicated in causing Parkinson's** or cancers*. Please "do your research" somewhere besides Natural News, FaceBook and YouTube.

* I've read the Seralini study and all I can say it that he did the equivalent of feeding Pug puppies with commercial dog food and then claiming the chow caused dwarfism and facial deformities.

** paraquat and rotenone, which are insecticides, not herbicides, and heavy exposure to them has been circumstantially linked to Parkinson's.

Anonymous said...

If roundup is non-toxic then why are Indian farmers committing suicide by drinking it? This is after they lose their butts trying to grow Monsanto's BT cotton.

Lazy Gardens said...

Anonymous ...
The short answer is: they usually use paraquat or other more toxic substances.

Here's the longer answer, and it's not pest-resistant cotton.

M. D. Vaden of Oregon said...

After one customer got me to try their way and an orange oil which proved useless, I have no interest to try vinegar.

As for Roundup, a huge advantage is spraying the leaves of small weed trees that grow in the midst of shrub roots. The Roudup only follows the stem and roots of the weed tree into the other root system.

If you like comparisons, some folks pull their hair out over the lasagna gardening vs. roundup thing. See:

Lazy Gardens said...

MD Vaden -
I'm one of those lazy gardeners. I lay down one layer of cardboard under the mulch as an initial weed suppressant. But the rest of my compost is just food scraps, kitty litter sawdust, and leaves and grass from the yard.

I hadn't thought about the impact of removing cardboard and paper from the recycling stream (assuming you are in an area that even HAS recycling) but if it takes less energy to re-make paper than use virgin materials it could be considerable.

matermark said...

Is 20% vinegar a permanent solution, or does it too need reapplications? I'm buying 99% acetic acid for under $10/liter (950ml) to try; I recently tried a recipe of 1 gallon 5% vinegar plus 2 cups epsom salts and 1/4 cup of Dawn. I actually used 6% Heinz vinegar, which should be 20% stronger, but applied the mixture later in the afternoon, which probably affected the outcome. Some of the weeds were quite tall, some over 12 inches, but my biggest problem is young nutsedge that is hard to eradicate--it snaps off quite easily.

Lazy Gardens said...

20% vinegar will need re-application every year, or when a new crop of weeds sprouts.

I found that the vinegar, salt, soap mix made the weeds wilt and some changed color, but they recovered and kept growing. The results were worse than genetic glyphosate, and cost more.

Nutsedge is extremely persistent - you have to kill the tops and keep killing them until the roots are exhausted and can't sprout any more.

matermark said...

When you mentioned that the vinegar/salt/soap mix made the weeds change color but they recovered, were you talking about 5%? My 99+% came in today and it was too windy but if it's nicer tomorrow, I'll try a batch 1:4 acetic to water.

That should put me around 20%... at 20%, do you use it as-is or do you add anything else like salt or epsoms, or just a spreader-sticker or dish detergent?


Lazy Gardens said...

I use glyphosate because I don't want to mess with nasty acids like 99% acetic acid. A few ounces of glyphosate in some tap water and I can kill anything with one application.

99+% acetic acid is NASTY stuff and will cause severe lung damage from the fumes. It is no longer "vinegar", it's ACID! WEAR the appropriate protective gear. If you have not researched what to use to safely handle this stuff, do it before you open the shipping container.

When I was a lab tech, one of the containers of it was handled wrong by the guys making a delivery and it leaked in the hallway. It ate through the commercial vinyl floor and was bubbling through the concrete. We wore hazmat suits with acid filters in the gas masks to clean it up, and had to evacuate the lab for a few hours to clear the fumes.

Even the 20% stuff has serious possibility for damaging the user with the fumes and liquid - read the MSDS and the application instructions for it before you do anything.


Oh ... and always add acid to water. Adding water to acid results in acid flying all over the room.

matermark said...

Just to clarify, when you said, "I found that the vinegar, salt, soap mix made the weeds wilt and some changed color, but they recovered and kept growing" were you talking about 5 percent vinegar or 20 percent vinegar?

I've used 41% glyphosate in the past, everything turned brown but if you pulled the weeds later (like a few days) depending on the weed, some grew back. Pennsylvania Smartweed, Nutsedge, Dandelion, and another unidentified weed that pulls easier at about 8-10 inches are my worse offenders, plus some common weeds that can be pulled easily like Lamb's Quarters are also a nuisance. I also have a Lemon Balm outbreak, but at least I have a use for it.

Lazy Gardens said...

I was talking about the popular grocery store vinegar, salt or Epsom salt and dish soap recipe that I tested.

I have never messed with the agricultural strength vinegar. it's only virtue seems to be that it's approved for use while maintaining your "organic" certification and that's not an issue for me.


Some weeds, especially if they have reached adult stage and have a good root system, are hard to kill even with glyphosate. They have enough energy reserve in their roots to resprout a few times.

Nutsedge is probably the worst, because of the multiple tubers.

Lambs quarters, because of the fuzzy leaves, is a bit resistant. Adding 1/4 teaspoon of dish detergent gets the weed killer past the fuzz by lowering the surface tension.

jolj1 said...

Nutsedge/ nutgrass has a herbicide that kills all lentil, this is why it can not be applied to peanuts.
But you are right that the nuts are hard to kill, I have found hogs do a good job.