Baking soda and weeds ... Baking Soda Looking for a safe way to keep weeds and grasses from growing in the cracks of your paved patios, driveways, and walkways? Sprinkle handfuls of baking soda onto the concrete and simply sweep it into the cracks. The added sodium will make it much less hospitable to dandelions and their friends. Try it 2x/yr, spring and fall. Site has other ways to kill weeds.