Lawn Seed Calculator

Lawn Seeding Guide

Seeding Rates

New lawn from seed: 35–50g per m² (higher rate gives faster establishment but not necessarily a better long-term lawn). Overseeding an existing lawn: 25–35g per m² — lower rate as existing grass fills gaps. Patch repairs: 50–70g per m² to ensure dense coverage in the repaired area. Shaded areas may need specific shade-tolerant seed mixes and can be sown slightly more densely as germination rates are lower.

Best Times to Sow

Spring (April–May): soil is warming but moisture is often adequate. Germination takes 10–21 days in good conditions. Main risk: spring can be dry — watering commitment essential. Autumn (August–October): the preferred time for most UK lawn professionals. Soil is warm from summer, air is cooler, rainfall increases, and there is less competition from weed seeds. Germination is slightly slower but establishment is generally more reliable. Avoid sowing in summer heat or winter cold.

Seed Bed Preparation

Good preparation makes the most difference to success. Dig or rotavate to 15–20cm, remove all perennial weeds including roots (bindweed, couch grass, thistle). Rake to a fine tilth. Apply pre-seed fertiliser (low nitrogen, high phosphorus) and rake in. Firm the surface by walking across it or using a roller — seed needs contact with firm soil. Final rake to create a criss-cross surface texture. Sow half the seed in one direction, the other half at 90° for even coverage.

After Sowing

Keep the seedbed consistently moist until germination — this may mean watering twice daily in dry weather. Never let the surface dry out during germination. Once established (5–6cm tall), first cut at the highest mower setting (5–6cm), removing no more than one-third of the blade height. Avoid walking on a newly seeded lawn for 6–8 weeks. Apply autumn lawn feed 6–8 weeks after sowing to strengthen roots before winter.