Keeping your lawn healthy can seem like a constant struggle. Weeds are hardy and quick-spreading, often quickly outcompeting your grass and colonizing your lawn if you let your guard down. Killing weeds without harming your lawn takes constant vigilance and the willingness to experiment with different methods to see which works most effectively.
For a cheap, non-toxic spot weed killer, you can't do much better than boiling water. Boil a kettle full of water and put on oven gloves and long pants to help prevent against accidental splashes. Pour a small amount of water over the weed from a low height so that it doesn't splash on your grass. For even more precision, pour the water through a funnel aimed directly at the bass of the plant. This method will kill both the plant and its seeds, normally preventing it from resprouting. If the weed does manage to regrow, simply treat it with more boiling water.
Spot killer herbicides are a tried and true method of weed control, but many homeowners would prefer not to add unnecessary herbicides to their lawns. For a non-toxic approach, use vinegar. Place pickling vinegar (which is stronger than plain white vinegar) in a spray bottle and spray it directly on the plant. It will kill leaves and stems but may require multiple treatments to completely kill off the root system of an established weed.
Rubbing alcohol is one of the best precision weed killers. Put it in a spray bottle or apply it with a cloth directly to the weeds to avoid accidentally spraying nearby grass. The rubbing alcohol will dry out the plant by sucking out extra water. It may require a few treatments to kill a particularly hardy plant.
Treat the Lawn
Spray your lawn with a weed-killing treatment (see Resources). There are treatments designed to kill grassy weeds such as crabgrass and nutgrass, broadleaf weeds such as dandelions, or both without damaging your lawn. Select a variety which is marked as suitable for the type of grass you grow, since certain strains of grass such as Saint Augustine grass and bahia can be damaged by certain weedkillers.