Homeowners generally have two ways to apply weedkiller when needed. Weedkillers are available in liquid or granular form, and the choice between them is often one of convenience. To get the most effective chemical, identify the weed and find the best herbicide for that plant. Remember, however, that your best defense against invaders is a healthy, dense lawn without bare spaces for weeds to germinate.
Any weedkiller created for use on lawn grass must kill broadleaf plants without damaging the grass itself, and companies have come up with quite a few chemicals that do just that. Each chemical, however, is usually a bit better at killing a few types of weeds and is less effective on others, and some can damage certain susceptible grasses. To get the most effective herbicide, educate yourself about the weeds typical in your area and the grass varieties in your lawn.
Applying a Liquid Weedkiller
Liquid herbicides are available as ready-to-use spray bottles or as concentrates. The premixed sprays are often more expensive per square foot, but if you have only a small area of problem weeds the extra cost may be worth it. Concentrates can be used in a tank sprayer, a hose-end sprayer or a spray bottle, but be sure you use that container for herbicides only, never fertilizer.
The chemical needs to be absorbed by the leaves of the weed for 24 hours to be effective, so spraying during a dry spell is important. Herbicides at temperatures above 85 degrees, however, can damage the lawn. To maximize the weed leaf area available, avoid mowing before spraying.
Herbicides are most effective on young, actively growing weeds. You might need to make another application if weeds are large, have strong root systems or have a leaf surface that repels liquids.
Advantages and Disadvantages of Liquid Weedkillers
Liquid herbicides excel at covering weed leaves thoroughly, enhancing absorption. You can also treat smaller areas more easily than with a granular formula. Mixing a solution from concentrate, however, can be annoying, and the chance of accidental contact with the chemical is increased. Like all herbicides, liquids are toxic, especially in concentrated formulas. You will need to beware of spraying on windy days, because the fine mist can drift onto ornamental plantings.
Many homeowners feel that weed control should be a simple matter of spray and the problem's gone. In reality, removing the weeds, even with a single application, is just the beginning. Plants germinate wherever there is bare ground, so fertilizing to thicken the lawn, mowing higher and reseeding bare patches are the only long-term solutions. Healthy grass is a great groundcover, and it will crowd out the weeds if you help it along.
Weedkillers are not appropriate for new lawns. Avoid any kind of herbicide for at least three months or, if possible, for four or five months. Since this is also the time when bare soil is most exposed, consider using a mulch when seeding to keep weeds from sprouting.