New lawns need time for their roots to become established before they can be mowed for the first time. For seeded lawns, it may take up to 2 months before they are ready to be mowed. Sod may be ready to be mowed within 2 to 3 weeks of planting. Three to six weeks are required for sprigs, stolons, and plugs to become established. For seeded lawns, wait for all of the seeds to germinate before mowing.