Over-seeding is the process of incorporating soil and seed to existing lawns to create denser, more uniform turf. Many times this technique is performed because the tree canopy has increased creating shady sites where sunny grass no longer thrives. This is also beneficial on lawns overgrown with weeds. This process is best performed in early spring or fall because of cooler temperatures and likelihood of rainfall. Optimal results are achieved when including over-seeding with aeravation and aeration.