Gravel driveways have some advantages over other types of driveways, including being less expensive and quick to install. However, one of the disadvantages is that the spaces in the gravel allow weeds to take root. These weed seeds remain dormant until the temperatures warm and then begin to grow. The best way to kill weeds in a gravel driveway is to use a combination of herbicides that kills both adult weeds and prevents germination of new weed seeds.
Fill a garden sprayer with a non-selective, post-emergent herbicide and dilute it with water if instructed to do so. Non-selective herbicides will kill everything they touch, so they are the best method to kill weeds in a gravel drive.
Spray the herbicide mixture onto each of the weeds in the gravel until each plant is completely saturated. Use care around the edge of the driveway since any overspray will kill nearby grass or vegetation.
Wait for three to five days and reapply the herbicide to any weeds that still remain green.
Wait until early the following spring and spray the entire gravel driveway with a non-selective, pre-emergent herbicide solution in a thin layer. Hold the sprayer close to the gravel so that it soaks down into the gravel. The pre-emergent herbicide will prevent the germination of all weed seeds still in the gravel.
Allow the weeds to grow until they are at least 2 inches tall, or taller. The taller the weeds, the more leaf space there is to absorb the herbicide. You can also kill adult weeds organically by pouring boiling water or white vinegar directly on the leaves.