When is the best time to overseed a lawn in the UK?

Autumn (September-October) is ideal as the soil is warm and moist. Spring (March-April) is the second-best option. Avoid overseeding in summer unless you can water daily, and avoid winter entirely.

Do I need to scarify before overseeding?

Yes, scarifying removes thatch and opens the soil surface, giving seeds direct contact with the soil. This dramatically improves germination rates compared to simply scattering seed on top of existing grass.

How long before I can mow after overseeding?

Wait until the new grass is at least 50mm (2 inches) tall before the first mow, and set the mower high. This usually takes 3-4 weeks. Mowing too early can pull out seedlings.

Should I use a different seed mix for overseeding?

Use a mix that matches your existing lawn type. General purpose mixes work well for most gardens. Fine fescue blends are better for ornamental lawns, and rye-heavy mixes for high-traffic family lawns.

GardenCalcs

Lawn Overseeding Calculator

Calculate seed quantity, preparation steps, and timing for lawn overseeding.

Lawn Area

Total area you plan to overseed

Lawn ConditionHow thin or bare your existing lawn is

Grass TypeMatch the seed mix to your existing lawn type

SeasonWhen you plan to overseed

Price per kg (optional)

Cost per kilogram of seed for budgeting

How We Calculate This

Seed rate depends on lawn condition: lightly thin areas need about 15 g/m\u00b2, patchy lawns 25 g/m\u00b2, and heavily worn lawns 35 g/m\u00b2.

The rate is adjusted for grass type and a waste factor is added for uneven spreading. The calculator also provides step-by-step preparation guidance and seasonal timing.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.