By Ken Lain, the mountain gardener

This week there has been a trending question at the garden center; so when Christy from Chino Valley asked, “Can I use Vinegar as an Organic Weed control?” I thought the topic worth reviewing.

If you want to get technical about it, the most natural, safest way to get rid of weeds is the ages old method: hand-removal. But, let’s face it; removing weeds by hand is not always feasible.  The weed in question may be too persistent, the area covered too extensive, or health restrictions may prevent any of us from being up to the task. For any of these reasons we turn to herbicides.

Is Vinegar an Herbicide?

Vinegar has shown promise as an effective weed control. There are several variables that alter vinegar’s effectiveness: age and type of weeds to be killed, and the concentration of acetic acid in the vinegar. Household vinegar is a 5% acetic acid solution. Stronger concentrations of 15, 20 and 30% acetic acid are also available.   All concentrations of acetic acid, including household vinegar, should cause treated foliage to brown within 24 hours.

Young, tender weeds and annual weeds like crab grass are susceptible to treatment with household vinegar. However, the roots are often not killed and the weeds may reappear within a few weeks. Repeated applications, up to three times, are needed for complete effectiveness with household vinegars.  Stronger concentrations of acetic acid work faster and their effects last longer.

What’s the Difference Between Acetic Acid and Vinegar?

Acetic acid is created by fermenting alcohol. Household vinegar has a 5% solution of acetic acid made from the fermentation of plant products like grapes and apples. There are stronger concentrations of acetic acid available and even synthetically created acetic acid. All vinegars contain acetic acid, but not all acetic acid is vinegar.

Is Vinegar Considered an Organic Control?

Yes, vinegar is considered organic if the acetic acid in the product is created by the distillation or freeze-evaporation of plants. This is the process used for making household vinegar or the stronger concentrations sold for home canning. Of course, acetic acid made by synthetic processes is not organic.

Will Vinegar Do Anything to the Soil?

Being an acid, vinegar can lower the soil’s pH a bit. It is, however, a temporary effect. Acetic acid breaks down quickly in water, so any residue will be pretty much gone after the first watering or rain.

It is possible to buy products with a higher acetic acid content (20%) than that found in household vinegar. Such products can be purchased at farm stores or from restaurant suppliers. Are there Stronger Vinegars?

Note – The potency of these high percentage acid products renders them unsafe. Also, the dyes, antibacterial agents, and other ingredients in various acids and dish soaps causes the organic gardener to say “no thanks”.

Are there Organic Alternatives at the Garden Center?

Burn Out is a relatively new vinegar-based herbicide.  Designed by Bonide, it is a blended mixture of vinegar and oils for a stronger knockout of local weeds.  Burn Out is approved for organic gardening and is safe to use around people and pets.

I’ve been experimenting with this new weed killer on all types of actively growing weeds and grasses. It appears to be rainproof once it has dried, it works at temperatures as low as 40 degrees, and does not infiltrate the soil. It is a candidate for use around borders, driveways, sidewalks, around the base of mature trees, around buildings, fence lines, barns and pastures, school grounds, in greenhouses, and other areas where safe weed control is needed.  Since birds are always welcome to our gardens, I’m pleased to report that it’s definitely bird friendly.