While grass looks great on the lawn, grass in flower beds or gardens or between paving stones on a walkway can be a nuisance. You can douse the area in grass killer, but you'll end up putting potentially harmful chemicals on the landscape, and you could render the area unsuitable for planting anything else. Another choice is to use an organic, non-chemical method for killing grass.
Cover the area with a thick layer of newspaper or cardboard. This method is effective for killing grass in a large area, such as a new flower bed or garden. The newspaper or cardboard blocks light and oxygen from reaching the grass. This method is simple, but it can take several months to kill all the grass.
Pour boiling water on the grass. Scalding water will kill the grass without harming other plants in the area. Heat a tea kettle or pot full of water, then carry it outside and pour it on grass growing between pavers on walkways or alongside flower beds, driveways or walls. Wear closed-toed shoes and pour the water slowly, holding the pot only a few inches from the ground to avoid splashing and burning yourself.
Spray vinegar on small areas of grass. Wet the area thoroughly. Repeat the application a few days later if any of the plant remains green. Household vinegar, which is usually a 5 percent concentration of acetic acid, is too weak to be effective. Studies by the United States Department of Agriculture have found that 10 percent to 20 percent solutions of acetic acid were effective in controlling weeds. You can purchase stronger solutions of vinegar at hardware stores.
Sprinkle salt on the area. Pour plain table salt in cracks between pavers or along the edges of the driveway to kill grass. This method leaves the soil inhospitable for any sort of plant growth, however, so avoid using it in flower beds or gardens.