Weeds are any plants that grow where they aren't wanted. A plant that is desirable in one location, such as Bermuda grass in the lawn, can become an invasive weed if the grass creeps into a vegetable garden or landscaping bed through broadcast seeds, stolons or roots. To control weeds, many gardeners resort to chemical weed killers. Chemical weed killers kill the plant. Some also kill the roots of the plant to keep it from returning. Because chemical weed killers will kill plants, and can harm humans as well, you need to apply them carefully.
Read all warnings and mixing instructions before handling chemical weed killers. Some weed killers are sold pre-mixed in spray bottles. Others are sold for bulk application in concentrate form. Mixing instructions vary among weed killer brands.
Time application of weed killer for the point when weeds have reached the specific stage for development when the weed killer brand will be most effective. This stage will be listed on the label of the weed killer. Choose a day that is not windy.
Put on protective clothing such as long pants, long sleeves, gloves, close-toed shoes and breathing protection before applying weed killer to keep the weed killer from touching your skin.
Mix herbicide concentrates according to the package instructions. A typical ratio for a herbicide mix is 1 part herbicide to 1 part water.
Pour herbicide into a spray bottle or holding tank of a large chemical sprayer to apply large amounts of the weed killer. Set the bottle's nozzle to apply a mist or jet of spray. Or, prime the pump of the chemical sprayer by grasping the handle and pumping it up and down until the pressure is built up in the holding tank and the handle will no longer pump easily.
Place a plastic drop cloth over desirable plants to protect them from chemical overspray. Weed killers will kill desirable plants as easily as undesirable ones.
Point the spray nozzle of a spray bottle or applicator wand of a chemical sprayer at the weed. Depress the trigger of the hand sprayer or chemical sprayer to release a jet or mist of spray over the weed. The hand sprayer will only shoot a single jet of chemical, while the nozzle will continue to release spray until you release the trigger.
Take a shower and launder your clothing when you have finished applying weed killer to ensure that you do not remain in contact with the chemical.