If you dislike the appearance of crabgrass in your garden or lawn, consider using a horticultural vinegar product to combat the invasion. "Crabgrass (Digitaria spp.)" can be any of about 27 species of tenacious weedy grass found in the continental United States. Crabgrass can be either an annual or a perennial that grows primarily in warmer climate zones.
Certain chemical herbicides, such as glyphosate, can kill crabgrass, but if you are concerned about using chemical products, a more natural alternative exists. Your crabgrass problem might be solved by using vinegar as an herbicide.
The higher the acetic acid concentration, the more effective the vinegar is in killing crabgrass and other weeds. Culinary vinegar has only five percent acidity, which might be strong enough for some weed-killing purposes, but for crabgrass you should use a stronger horticultural vinegar. Look for a horticultural vinegar with an acidity of 10 to 20 percent.
Mixing a Horticultural Vinegar Spray
Use typical mixing ratios as used with other liquid herbicides in lawns:
- If you have a small number of crabgrass plants, mix one
quart of horticultural vinegar with three quarts of water in order to treat 250
square feet of lawn.
- For a large number of plants, mix one quart of
horticultural vinegar with one quart of water in order to treat 100 square feet
Applying Horticultural Vinegar
Spray horticultural vinegar on a warm, sunny, windless day to maximize the vinegar's effectiveness. Keep an eye on the weather forecast and avoid spraying when rain or wind is predicted within 24 hours after you spray. Wait at least 24 hours after rain before you spray.
Pour the appropriate amounts of vinegar and water into a spray bottle or hand sprayer.
Spray all visible crabgrass, soaking it thoroughly, but being careful to keep the spray from other plants.
Pull crabgrass plants from their roots after they
wilt and die. Leaving the plants in place can result in them re-rooting and continuing to grow. Dispose of dead plants in your community's green waste recycling center; do not add to your compost.
If you see a new growth of crabgrass, reapply the vinegar spray.
- Keep horticultural vinegar away from children and pets. High concentrations of acetic acid, contained in 20
percent acidity vinegar, can pose hazards to human health; vinegar is corrosive and can cause permanent eye damage.
- You should wear protective
clothing and eyewear when using any such product. This includes long-sleeved shirt, long pants, socks, waterproof boots, hat, waterproof gloves, and goggles or a face shield.
- Vinegar is nonselective and can kill lawn and other plants if the spray extends beyond the target. Use caution and limit the areas where you use this product. Also consider using a smaller applicator, such as an eye dropper or a paintbrush.
- Occasional use of vinegar for crabgrass control will not alter your soil’s pH acidity balance. However, if you use vinegar once per week or more often, the acidity of your soil might increase, making it less suitable for plants that require a more alkaline soil, such as clematis, coral bells, delphinium, mock orange or Japanese barberry.
David Montoya is an attorney who graduated from the UCLA School of Law. He also holds a Master of Arts in American Indian studies. Montoya's writings often cover legal topics such as contract law, estate law, family law and business.