Fall Overseeding Playbook

When to Overseed

Fall overseeding targets a soil temperature window of 50-65°F trending downward, with air temperatures of 60-75°F. You need at least 45 days before your first average frost date for seed to establish.

The 8-Step Process

1. Mow low — Cut existing grass to 2 inches to reduce competition
2. Aerate — Core aeration creates seed-to-soil contact points
3. Dethatch if thatch layer exceeds 0.5 inches
4. Spread seed at the overseeding rate (50% of new lawn rate)
5. Apply starter fertilizer — high phosphorus (e.g., 24-25-4)
6. Top-dress lightly with compost if soil is compacted
7. Water — begin the seeding watering protocol (3x daily, light)
8. Protect — avoid foot traffic for 3-4 weeks

Pre-Emergent Conflict

If you overseeded in fall, your spring pre-emergent strategy changes. Standard prodiamine is safe because fall-seeded grass has established by spring. The only exception is if you seeded very late (less than 45 days before frost) — in that case, use mesotrione (Tenacity) which is seeding-safe.

Watering Schedule

The first 14 days are critical. Water 3 times daily for 5-7 minutes each session to keep the top 0.5 inch of soil consistently moist. After germination, gradually reduce to once daily, deeper watering. The Lawn Sense watering calculator automates this transition.

When to Start Mowing

Wait until new grass reaches 3.5-4 inches, then mow at the normal height. This typically takes 3-4 weeks after germination. Count your mows — after 3 mows, seeding restrictions are lifted and you can resume normal herbicide applications.