Proper care of your lawn and garden allows the desired plants to thrive and block out weeds, but unwanted plants are still often able to grow. Herbicides are effective at killing the weeds when the type of weed killer is carefully selected to match your needs. Selective herbicides kill only a specific type of weed or plant, while nonselective herbicides kill any plant they reach. You also have the option of using a preemergent weed killer to control weeds before they grow or a postemergent herbicide that is effective once the weeds are already growing. Contact chemicals kill the weeds when they touch them, while systematic herbicides travel through the weeds to kill them from the inside.
Physical removal of weeds requires strenuous digging and pulling by hand. Getting on hands and knees to pull the weeds puts strain on the back and legs. Some weeds have long roots that require extra digging to remove the entire weed. A chemical weed killer is easier to apply because you only need to spray it on the plant. The herbicide takes over at that point to kill the unwanted plant.weeds to kill them from the inside.