by Ken Lain, the mountain gardener
Vinegar experiments have been conducted in the Lain gardens with interesting results. Vinegar and herbicides made with acetic acid show promise as broad spectrum herbicides.
Effectiveness seems to depend on the type of weed, its maturity, and the concentration of acetic acid in the vinegar. Household vinegar is a 5% acetic acid solution. Stronger concentrations of 15%, 20%, even 30% acetic acid are also available, but as they are highly caustic, be careful handling these stronger concentrates. All concentrations of acetic acid, including household vinegar, seem to cause weed foliage to brown some within 24 hours.
Young, tender weeds like crab grass are highly susceptible to treatment with household vinegar. However, the roots are often not killed and the weeds reappear within a few weeks. Repeated applications are more effective, and stronger concentrations of acetic acid work even faster with a better, longer, knock down.
Vinegar works really well on weeds between the cracks in sidewalks. I suspect that the heat from the pavement helps the process. I’ve had less luck with vinegar on perennial weeds and those that grow in shady areas; they turned black, but rallied and grew back. These tougher areas needed a couple of repeat applications at 3 day intervals to eventually die back. Sadly, they reemerged again in a month or so.
You can find stronger concentrations of vinegar sold for canning purposes. These work faster and longer than household vinegar, but are caustic and should be handled with extreme caution. Keep it off your skin and away from your eyes!
All vinegars contain acetic acid, but not all acetic acid is 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. Stronger concentrations of acetic acid and even synthetically created acetic acid are available.
If the acetic acid in a product is created by the distillation or freeze evaporation of plant sources, like household vinegar or the stronger concentrations sold for home canning, it is considered organic. Acetic acid made by synthetic processes is not.
Being an acid, vinegar can lower a soil’s pH a bit. However, acetic acid breaks down quickly in water, so any residue is gone after the first irrigation cycle or rain.
To use acetic acid as an herbicide: 1. Spray directly on the foliage and try for saturation without much run-off. 2. Don’t apply before watering or if rain is expected, as water breaks down acetic acid. 3. Avoid spraying on windy days to prevent this killer from drifting onto plants you don’t want to damage or kill.
I had much more success with BurnOut by Bonide, which showed better results and was much safer than the super strong vinegars. This product mixes a stronger solution of citric acid with clove oil. The dual combination allows the stronger acid to penetrate deeply into the leaf and stick to local weeds better than straight household vinegar did. BurnOut is difficult to find locally, but is available in three different sizes at Watters Garden Center.
My personal goal is to keep my vegetable and herb gardens organic for my family’s health, for our pets, for the birds, but finding an effective organic product that really works has been difficult. BurnOut is approved for organic gardening, and safe for use around people and pets. It killed all types of actively growing weeds and grasses while proving remarkably rainproof once it was dry. BurnOut worked really well around borders, driveways, sidewalks, even around the base of mature trees, around buildings, fence lines, barns and pastures, in the greenhouses, and other areas where it was applied.
After experimenting with so many different types of vinegars I unflinchingly recommend the switch from vinegar to BurnOut for our Watters customers.
FREE Gardening Class on July 16 is about Perennial Summer Flowers. These impressive bloomers come back year after year. Increased rain in July makes this the ideal month to plant perennials. Students will learn how to design for a continual four-season bloom in a garden or landscape. Emphasis will be given to local native bloomers.
Until next week, I’ll be helping gardeners kill weeds here at Watters Garden Center.
* Disclaimer – Vinegar is not labeled for use as a herbicide, so I’m really not able to recommend its use. But experiments as a gardeners is recommended. I can recommend the us of Burnout by Bonide corporation because of its label and Arizona registration. Household vinegar works well on young weeds. Repeated applications seems to improve effectiveness. Don’t bother trying to kill older weeds, thistle and perennial weeds with vinegar They simply grow back to quickly. Switch to stronger caustic solutions or Bonide’s fast acting ‘BurnOut’ for a better weed killing experience that still keeps the garden organic.