My lawn is a mess. What is the best way to kill my grass and start over?
If your lawn is predominantly weeds and mixed species of grasses, it may be easier to completely renovate the lawn than manage what is already there. The first thing you should do is apply a nonselective herbicide (e.g., glysophate) across the entire lawn. Contact your local Extension office for herbicide recommendations.
During the weeks following the treatment, while the grass and weeds are beginning to die, it is important to keep good soil moisture so that weeds that are not completely controlled will regrow and can be sprayed again. It is usually best to apply the herbicide two or three times, three or four weeks apart to make sure you kill all of the weeds that will be difficult or impossible to control after the lawn is seeded.
Once all of the existing vegetation is dead, it will be necessary to till the soil and prepare a proper seedbed prior to seeding. A proper seedbed is firm enough to walk on without leaving deep footprints but loose enough to allow the seed to be lightly raked into the soil. Once the seed is applied at the proper rate, keep the soil moist for a couple of weeks until the seedlings have emerged and developed a significant root system.
Very early in the rejuvenation process, submit a soil sample for testing by your local Extension office. If soil test indicates that the pH needs adjusting, this is the best time to do so. If lime is needed, it must be incorporated into soil by disking or tilling and given time to become effective. The last step in seedbed preparation is amending with fertilizer as indicated in the soil test done earlier; this should also be disked or tilled into soil. Now, sow your seed.
After grass reaches recommended cutting height, begin regular mowing. You want to be sure new sprouted weeds do not gain the height advantage over grass. Also the most popular warm-season grasses are encouraged to spread by regular mowing. Keep mower blades sharp; your goal is to cut grass not rip it. Cutting helps prevent diseases getting a start in torn grass blades.