Disadvantages Of Using Vinegar In The Garden (& What To Use Instead)

A staple in most pantries, vinegar can be a versatile cleaning tool that seems to do it all. Among its endless list of uses, some gardeners even turn to vinegar to use as a weed killer. But before you start spraying, there are some important disadvantages of using vinegar in the garden that you should know about. Tiffany Selvey, House Digest's Garden Editor and in-house Master Gardener states, "In gardening, as in life, there's no single solution to every problem. While vinegar can be useful in managing some weeds, it may not be effective for everything, as I learned when I tried it in a DIY weed killer. In fact, in some situations, it can do much more harm than good."

To start, you need to know your types of vinegar. The household stuff that's probably in your pantry right now usually has a 5% concentration of acetic acid. The herbicidal vinegar that's used as a weed killer comes in concentrations as high as 30%. Household vinegar may be too weak to get the job done. But even if you get the right kind, there are still some important downsides to note.

Herbicidal vinegar can kill weeds, but it's not as effective as some of the other herbicides out there. It can also be harmful to you, your plants, and your outdoor furniture if not used carefully. From solarization to hand pulling to boiling water, there are options other than vinegar that are safer, cheaper, and easier.

Research does show that vinegar, especially the 20% or 30% concentration formulas sold as horticultural vinegar, kills weeds. When applied properly, it can kill 90% or more of treated weeds. To get those results, you need to spray enough to ensure that the entire weed is covered in vinegar. Then, you need to reapply it multiple times. The reason for this is that vinegar acts as a contact herbicide. It burns the parts of the plant that you sprayed it on, but it doesn't spread into the roots. On young or tender weeds, this contact burn can kill the entire plant. But older perennials with strong root systems will just put out new growth from their roots.

Vinegar also has no residual activity in the soil so weeds that germinate after you spray won't be affected. In a study published in HortTechnology, it took 4 or 5 retreatments of a weedy plot with a 20% or 30% acetic acid formula to achieve 50% weed reduction. By comparison, glyphosate only needed to be applied twice to achieve the same amount of weed reduction.

If you're looking for an herbicide alternative that works as well as glyphosate, skip the vinegar. The best alternative depends on where you're using it. In your lawn, regular mowing can be enough to prevent many weeds from growing and spreading. In flower beds, a 3 to 4-inch layer of mulch can smother existing weeds and prevent new ones from sprouting.

Some gardeners turn to vinegar as a natural alternative to harsh synthetic herbicides, but being a natural herbicide doesn't guarantee that it is safer.  Acetic acid, the key compound that gives vinegar its plant-killing abilities, is corrosive. Especially when using the high-concentration formulas that work best as weed killers, you can get hurt if the vinegar gets on your skin, in your eyes, or inhaled into your lungs. You need to wear proper safety gear when using it, just as you would with a synthetic herbicide.

In fact, if toxicity is your main concern, acetic acid is actually more toxic than glyphosate based on its LD50 rating. Though, it's important to note that both compounds have toxic properties and need to be used with care. Glyphosate and vinegar can both cause damage to your garden and your health if you don't take the proper precautions and follow the directions on the packaging when you use them.

If your goal is to find a safer weed killer alternatives to glyphosate, consider non-chemical strategies like sheet mulching. This method involves smothering the area in a way that can kill both existing weeds and the bank of weed seeds in your soil, all without relying on chemicals. If you don't have the time to wait for this slower method, simple hand pulling can give you immediate results. However, you'll have to stick to a regular schedule of pulling to keep the area weed-free throughout the growing season.

Budget-conscious gardeners who are looking for a cheaper alternative to store-bought herbicides might end up paying more if they opt for vinegar. While a single bottle of horticultural vinegar might be cheap, you'll likely need about 3 or 4 additional treatments. The extra product needed could make your total cost higher than it would have been for 1 or 2 treatments with a glyphosate-based herbicide.

In one report from the University of California's Hopland Research & Extension Center, it took 46 gallons of acetic acid per acre of annual vegetation followed by a second application of 6 gallons per acre to achieve similar weed control results as a single application of 2.4 gallons of glyphosate over the same area. This resulted in a total cost of over $1,800 per acre for the vinegar compared to a little over $100 per acre for glyphosate. If you're just treating your own garden, the cost difference likely won't be as dramatic. But you could still end up spending the same or more than you would on a commercial herbicide since vinegar typically requires multiple applications.

If you really don't want to use commercial herbicides, solarization is another low-cost option for killing weeds in a large area. This method involves laying a tarp or other light-blocking material down on the weedy area and leaving it there through the summer. The heat created will trigger weed seeds in the soil to germinate while blocking them from the light they need to grow.

Vinegar is a non-selective herbicide. It will harm any plant it comes in contact with, both the weeds and the plants you actually want to keep. If you're not careful about how you apply it to the weeds in your yard, it may end up splashing or drifting onto your flower beds or lawn. A limited amount of vinegar spray drifting onto established perennials or ornamental shrubs might not kill them, but it may cause visible damage to the leaves or flowers it comes in contact with. If you're using vinegar to control weeds near newly planted beds or newly seeded lawns, that drift may be enough to kill the tender seedlings before they can get established.

To manage weeds that are growing near your desirable plants, it's better to stick with methods that have little or no risk of harming any non-target plants. For a minor outbreak or weeds that are still young, stick with hand pulling and do your best to pull up the entire root with each weed. For a larger outbreak or more established weeds, look for a targeted herbicide that will kill the type of weeds you have without affecting your nearby desirable plants.

The key ingredient in vinegar is acetic acid. Like many acids, it is corrosive. Hard surfaces like concrete or metal won't be destroyed instantly. But with the repeat treatments needed to kill weeds, vinegar could end up causing stains or etching in cement, masonry, and other hardscape materials. Likewise, vinegar causes corrosion on most metals, including aluminum, steel, and tin that you might find in gardening tools and outdoor furniture.

You can generally prevent damage by rinsing the surface immediately, but then you also need to avoid rinsing the vinegar off of the weeds you're targeting. Depending on where the weeds are, rinsing off your driveway, patio, or aluminum siding without rinsing off the weeds you're trying to kill may not be possible.

If you need to treat weeds near your patio or any structure, opt for a less corrosive method. To tidy the edges along a patio or driveway, for example, you can run a string trimmer along it every couple of weeks during the growing season. For a long-term solution, consider edging these areas with dense ground cover plants or a thick layer of mulch to suppress weeds. To kill weeds growing through cracks and between pavers, try pouring boiling water on them. Just make sure the water has hit a rolling boil and reached a temperature of 200 degrees Fahrenheit or higher. Use a kettle or sealed pot to minimize heat loss as you carry it from the stove to your patio.