When to plant grass seed

For a cool-season lawn, seed in late summer to early fall, with the exact window shifting by region.

The window: Late summer to early fall is the ideal time to seed a cool-season lawn; in Illinois that means early August to early September in the north, mid-August to mid-September in the central part, and September in the south.

Cool-season grasses grow best in the spring and fall and less actively in the summer.
Seeding in late spring through mid-summer often leads to problems as summer heat slows or stops grass development of cool-season grasses.
Cool-season turfgrass is best planted in late summer to early autumn, framed as mid-August to mid-October.
Warm-season turfgrass is planted in late spring and early summer, framed as mid-May into June.

The mistake to avoid: Avoid seeding a cool-season lawn in late spring through mid-summer, because the summer heat slows or stops grass development.

Timing varies by region and year; your local extension office is the closest authority.

Grounded in: content.ces.ncsu.edu, extension.illinois.edu, extension.umd.edu. Every timing follows sentences verified verbatim on those pages.

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