Answer: Borax (sodium tetraborate, a white, crystalline mineral salt) has been found to be an effective herbicide for creeping charlie (Glechoma hederacea, also known as ground ivy, creeping jenny and gill-over-the-ground). Creeping charlie is an invasive perennial weed that vines throughout lawns and chokes out grass. Since the 1920s, borax detergent has been used as an herbicide to eradicate weeds, but it has only recently been tested scientifically for effectiveness on creeping charlie.
Borax contains boron which is an essential micronutrient that aids in sugar transportation in plants. However, in minute excess amounts, boron has a toxic effect on creeping charlie.
Borax must be applied with great caution because boron remains immobile in the soil and can accumulate to form a "hot spot" in the lawn. Boron toxicity results in yellow and brown spots around edges of leaves. Stems wilt and eventually the weed dies. Established grass appears to withstand the minute excess of boron needed to kill creeping charlie, though it may show brown discoloration temporarily. If the borax solution is applied in too high a concentration, or repeatedly, it will then be toxic to grass and many other plants.
This treatment can be applied only once each year for two years. If you still have creeping charlie problems, then switch to a standard herbicide.
Before applying borax as a herbicide be sure to test your spraying technique and the rate at which liquid sprays from the nozzle. Fill the sprayer with water and walk at a constant pace, passing back and forth over an area the same size as the one to be sprayed with borax. Your goal is to walk fast enough to empty the sprayer tank, spreading its contents evenly over the entire area.
Apply borax when creeping charlie is actively growing in the spring, when no rain is expected for 48 hours. The borax treatment appears to be most effective during warm summers when soil moisture is ample.
Remember: The borax recipe has been tested only on creeping charlie and is not to be used on other broadleaf weeds. Be sure to use the borax spray only in the lawn because research shows established grass is tolerant of the spray. It should not be used in gardens.
Borax Solution for Creeping Charlie Control:
Dissolve 10 oz. Twenty Mule Team Borax in 4 oz. (? cup) warm water.
Dilute in 2.5 gallons of water.
This will cover 1,000 square feet. If you have a smaller area to treat, cut the "recipe" accordingly.
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