The Scotts Miracle-Gro Company created a product called Roundup used to kill grass and weeds in lawns, sidewalk cracks or around driveways. Roundup comes in a ready-to-use formula and a concentrate. The concentrated Roundup must be mixed with water before you can spray it on your lawn. Applying it at the wrong strength can cause damage to the soil in your lawn, so it is important that you follow all of the directions on the product label.
Pour 5 tbsp. of Roundup in your backpack sprayer. This is the measurement to cover 300 square feet of lawn. If you have a larger area that you need to cover, double or triple the numbers. For example, you would use 20 tbsp. of Roundup to cover 1,200 square feet of lawn.
Add a gallon of water to your backpack sprayer. Again, this will cover 300 square feet of lawn. Multiply the numbers again if you need to cover a larger space. For example, 4 gallons of water will cover 1,200 square feet of lawn.
Put the cap on your backpack sprayer and give it a shake to combine the two ingredients.
Spray the Roundup over the areas of your lawn where you want to kill grass and weeds. Scotts recommends waiting for the temperature outside to consistently remain above 60 degrees F before you apply the Roundup to your lawn.