Will Boric Acid Kill the Lawn?

by Amanda Flanigan

Mothers know how expensive it is to raise children and are often on the lookout for ways to cut costs in certain areas of their home. One way is to forgo gardening products with a high price tag, opting instead for cheaper yet effective items. Boric acid, for example, is a versatile chemical that can help you maintain your garden and landscape. If not used properly, however, boric acid can harm lawns and pose a potential threat to plants.

1. The Ins and Outs of Boric Acid

Boric acid -- also called orthoboric acid -- contains boron, and is naturally found in soil, rocks, water and plants. It was registered for pesticide use by the United States Environmental Protection Agency in 1993. When used to control insects, boric acid serves double duty as an abrasive material cutting through the pests’ exoskeleton and as a stomach poison when ingested. Boric acid is available in various forms including dust, granular and wettable powder. Boric acid is sometimes confused with borax, which is a common household product used as a cleaning agent and laundry booster. They are not the same thing.

2. Does Boric Acid Kill Lawns?

Boron is an important nutrient that plants need in small doses, but too much boron will kill plants and turfgrass. Established grass appears to withstand the amount of boron needed to control certain species of weeds, according to the University of Minnesota Extension. For instance, the invasive creeping Charlie (Glechoma hederacea), which thrives in U.S. Department of Agriculture plant hardiness zones 4 through 9, can be controlled by mixing 10 ounces of borax -- which contains boric acid -- with 1/2 cup of water before diluting with another 2 1/2 gallons of water. This will treat an area measuring about 1,000 square feet and should only be applied once a year for two years. Any more boric acid than this will cause the grass to brown, wilt and eventually die. It works by drying out the plant and interfering with the photosynthesis process.

3. Gardening with Boric Acid

Boric acid has many helpful uses in and around your garden. It can be used to fertilize the soil, correcting any areas with a boron deficiency. However, always perform a soil test to ensure your soil has a boron deficiency before applying boric acid. You can also use boric acid to create a homemade bait station to kill ants in your lawn. These stations are created by soaking cotton balls in a solution of 1 teaspoon of boric acid, 8 teaspoons of table sugar and 1/4 liter of hot water. Place the soaked cotton balls in a small glass jar with holes poked in the lid. When positioned along the ants’ path, they will enter the jar through the holes and carry the bait back to their nests.

4. Boric Acid Safety Concerns

Boric acid can cause health complications if used improperly. It typically doesn’t cause skin irritation unless the skin is damaged, then it can be absorbed. If inhaled, the boric dust leads to throat and nose irritation, including coughing, sore throat and dryness. When ingested, boric acid causes gastrointestinal disturbances including vomiting, diarrhea and abdominal pain. Keep boric acid out of reach of children and pets, and keep children, pregnant woman, nursing mothers and pets out of the area until the boric acid has settled. Always wear protective clothing -- such as rubber gloves, safety glasses, dust mask, and long-sleeve shirt and pants -- when using boric acid.