Lawn aeration and overseeding in Windham, Maine.

On the glaciomarine silts mapped in lower parts of town, such as Scantic and Buxton, compaction and poor drainage compound each other. NRCS describes Scantic soils as poorly drained, with a slowly permeable subsoil, so water sits in the root zone after rain. Pulling cores improves air and water movement where it is needed most.

On the sandy Hermon and Windsor soils, compaction is less of a problem than thin turf. There, aeration is mostly about seed-to-soil contact, so overseeding can thicken a lawn that thins every dry summer. Choosing fine fescue in the seed mix suits that ground, since Extension rates it as tolerant of dry soil.

Extension names late summer to early fall as the best time to seed, and puts the ideal lawn seeding window at August 15 to September 15, when soil is still warm and nights are cool. Our window runs from late August through early October. In zone 5b that leaves new seedlings several weeks to root before the ground freezes.

Lake properties add one more consideration. Overseeding is often paired with fertilizer, and on lots draining to Highland Lake or Little Sebago, which the town lists among its most-at-risk waters, a soil test first keeps phosphorus from going down where it is not needed.