Aeration can be performed in the spring or fall, however we always suggest that it be done during the fall season from late August through mid-October. Lawn Aeration in spring has many drawbacks. First, it degrades the quality of crabgrass pre-emergent applications. This is especially true if the aeration is done after the pre-emergent application, because aeration disrupts the barrier that the pre-emergent creates. Second, after aerating the lawn needs time to rejuvenate and recover. The lawn is a little weak after aeration, and if done in spring this opens the possibility for significant weed issues. However, sometimes spring aeration/seeding is necessary. Common situations where we would recommend doing the service in spring is when there is damage from previous seasons, equipment damage from landscape work and any time the lawn is bare and is in need of new seed.