Aeration & Overseeding

Late August, not spring

Cool-season grasses in Connecticut germinate best in warm soil under cooling air, which in this part of the valley means roughly the last two weeks of August through mid-September. Seed put down in April competes with crabgrass for the whole summer and usually loses. Seed put down in October runs out of growing season before it roots.

Core aeration pulls plugs out of the ground rather than punching holes through it, which is the difference between relieving compaction and adding to it. Seed goes into those open cores the same afternoon, while they are still open, because soil contact is most of what determines whether a seed becomes a plant.

What the program looks like

• Core aeration — plugs pulled and left to break down, not spike-rolled
• Seed dropped into open cores the same afternoon for soil contact
• Species matched to the site: fine fescue in shade and along walls, tall fescue on hot pavement edges, bluegrass where it can be watered
• Starter nutrition without phosphorus unless a soil test calls for it
• A written watering schedule for the first three weeks — the part that decides the outcome
• A germination check about three weeks after seeding