Crabgrass is a fast-growing, warm-season, annual weed. It grows in mid-summer and over-winters as seed. The fall frosts kill crabgrass, but the seeds stay viable throughout winter. If the lawn turf is thick and healthy, it is difficult for crabgrass to take root. In areas of drought or where there are water restrictions, crabgrass takes hold. Keeping the grass cut higher also helps to prevent crabgrass, as the seeds must have sun to germinate.
Mix 1 gallon of white vinegar with 8 drops of liquid dish soap to help the plant material absorb the vinegar. Pickling vinegar, which is nine percent vinegar, works better than household vinegar, which is only 5 percent. Spray the solution on the weeds until the weeds are completely covered. You might need more than one treatment, especially for the larger, stubborn weeds and crabgrass.
Sprinkle table salt liberally on crabgrass and other weeds (you don't have to bury the crabgrass/weeds). Salt kills crabgrass, but it also causes damage to the soil if used too often. Salt might also kill tender plants and grasses, so only use salt where you do not want other plants and grasses to grow. Salt applications are perfect for the cracks in sidewalks and driveways, edgings for landscaping or the edges of the sidewalks and driveways.
Salt and Vinegar
For particularly stubborn crabgrass that tries to invade walkways, patios, sidewalks and driveways, make a mixture of 1 gallon vinegar and 1-¼ cups table salt. Mix well, so that most of the salt starts to dissolve, then spray the weeds until they are completely covered.
Corn Gluten Meal
Sprinkle corn gluten meal liberally on crabgrass and other weeds. Corn gluten meal (not regular corn meal) is a deterrent. It deters spreading weeds, including crabgrass, dandelions, knotweed, curly dock, pigweed and plantain. Corn gluten meal is safe to use on lawns and flowerbeds. It also is safe for vegetable gardens. The corn gluten meal should be labeled as "pre-emergent herbicide." The protein in the corn gluten meal is what affects the seeds. Corn gluten meal from feed stores does not have enough protein. Do not use corn gluten meal on areas where the seed is still in the germination process.