Know Your Enemy
No single herbicide, weeding technique or lawn care tactic works against all weeds. How you attack the weeds in your lawn depends on which you have. Lawn weeds fall under three broad categories: unwanted grasses; grasslike plants called sedges; and broadleaf plants. Most are annuals or perennials. Annuals complete their life cycle in one season and reproduce from seeds. Perennials live several years and spread underground as well as by seed, making them harder to control.
The following guide shows examples of the different types of weeds that plague lawns throughout the country. If you're still stumped about whether yellow nutsedge or yellow woodsorrel has invaded your turf, call the extension service in your area for help from experts.