Pet-friendly Weed Killer - Vinegar

I have a large (fits 8 cars) stone driveway. My NJ Dog walks on the driveway getting in and out the car. He has a paw licking fetish. There is also an 18 mo old, that occasionally, likes to pick up stones. As small weeds slowly started to sprout, I searched for a dog / kid friendly solution.

Pouring boiling water on weeds in the sidewalk cracks seemed to be the friendliest. However, given the size of the area, this didn’t sound very practical.

I came across several ‘recipes’ using vinegar. The internet has arguments as to why Roundup is less toxic (my coleslaw doesn’t buy it). In addition to vinegar, various recipes added dish detergent, salt, gin, or water in differing proportions. One site (see links below) had tried three recipes and had pictures. It seemed to confirm the results I had come across on several other websites.

1. This ‘weed killer’ kills the leaves of everything it touches (including grass and flowers).
2. It doesn’t kill the roots.  However, repeated applications may prevent the root from getting any nourishment, so it dies by default.
3. You need to spray the mixture on the leaves – preferably on a hot, sunny day, with little chance it will be washed away.
4. Some plants seem to be more resistant to the effects of vinegar than others.
5. I re-spray every week to 10 days – this is not a long-acting solution.
6. Vinegar is acidic.  It can change the Ph of your soil and kill the good microorganisms in the soil. Try to avoid spraying the soil.
7. Stronger concentrations of vinegar can be purchased at some garden stores, but the increased acid concentration will increase the chance of negative side effects.  Acid can cause eye and skin irritation or an allergic reaction.    
8. My son complains the driveway smells like coleslaw after I’ve sprayed.

I mixed 1 gallon of white vinegar ($2.73 @ Walmart) with a squirt, 2-4 oz of dish detergent (Ajax was $1.00 at the dollar store). I’ve seen several sites recommend Dawn, but Ajax has worked fine for me. This provided me with 2+ applications. Compare to Roundup 1.25-Gallon Weed & Grass Killer Refill at Lowes for $13.97 and vinegar is a cheaper alternative (remember, vinegar doesn’t kill the roots and Roundup does).

I used a gallon sprayer – the kind with a short hose & nozzle where you pump up the pressure. It emits a light mist that covers the leaves but is easy to control.

White vinegar purchased in the grocery store contains about 5% acetic acid, which is the active ingredient. The acetic acid draws the moisture out of the pant’s leaves and they wither, turn brown, and dry up. In the sun, a plant needs more moisture, so spraying vinegar on a hot, sunny day can cause the leaves to turn brown in a couple of hours.

Adding soap to the vinegar helps it stick to the leaves, rather than just running off.

Salt also draws moisture from leaves but unlike the vinegar, it gets into the soil and can affect plant growth long after it is applied. It also destroys concrete. Avoid salt.

Water will dilute the concentration of the acid.

Gin?.....belongs in tonic water with a lime wedge when you are done spraying!

Most of the weeds (there seem to be four distinct varieties that like my driveway) are brown within 2 - 4 hours. One variety is a bit more resistant and is yellowy within a few hours. The younger weeds are goners. Most of the more established plants are wounded, but new leaves may start to appear in 7 – 10 days. After the third application, almost all weeds are dead.

The paw licker has shown no adverse effects from trotting across the driveway. However, I don’t let him walk on it after I’ve just sprayed.

Vinegar works for me. It isn’t for every weed-killing situation and you need to be diligent in re-spraying. As with any substance, too much can be harmful – to the soil and the dog. But if you have a patch of weeds, where you don’t want anything growing, give vinegar a try. Let me know how it works for you.