If you want to kill all the weeds in a specific area you can try what’s known as a non-selective herbicide such as Round-up Quick PRO weed and grass killer or other non-selective herbicides. If the undesirable weeds are in your lawn you can use what’s known as a selective herbicide, these are designed to eliminate broadleaf or grassy weeds without harming the lawn grass, you can also use a fertilizer known as a Weed & Feed type, it will get rid of the weeds while feeding your lawn. If the problem weeds are in ornamental beds then you have to be careful when applying the herbicide most broadleaf weed control products can injure plants, so read and follow the instructions on the product’s label.