The best time to battle dandelions is when they're seedlings, between mid-spring and early fall. Each plant produces up to 2,000 seeds a year, so get them when they're young!
One way to kill dandelions is to use a systemic selective herbicide for dandelions in your yard or a nonselective herbicide for dandelions in your patio or sidewalk. Spray on a windless day when the temperatures are between 60 and 85 degrees Fahrenheit (15.5 to 29 degrees Celsius) [source: The Lawn Advisor].
If your municipality bans herbicides or you don't want to go the chemical route, there are some natural ways to kill dandelions.
- Dig up the dandelions by the root with a shovel, weeder, dandelion "digger" tool or aerator. The root, called taproot, can grow up to 18 inches (46 centimeters) long! You must remove the whole root or it will grow back.
- Spray horticultural vinegar on dandelions that aren't in your lawn or garden. Don't use it in your garden because it will kill any plants in its path.
- Put a teaspoon of salt at the dandelion's base when the weather and soil are dry. The salt will eventually kill the dandelion's roots. Apply more salt if necessary (e.g. if the salt blows away or if it rains before the salt kills the dandelion). Always make sure not to get salt on any other plants. This is a cheap, natural way to kill dandelions [source: Gardening Tips].
If these methods don't work or if you just don't have the time and energy to take care of the dandelions, a lawn-treatment company can take care of your dandelions for you.
Note: To prevent dandelion growth, keep your grass no longer than 2.5 inches (6 or 7 centimeters) long and reduce the acidity of your soil with mulch or compost. You can also apply corn gluten herbicides in the spring and fall, four to six weeks before dandelion seeds germinate [source: Professor's House].