Keep the soil around newly sown grass seed moist while it germinates. When rain is not enough, use a fine spray or watering-can rose so the water does not wash seed into piles. Check the seedbed regularly: a sunny, windy patch can dry much faster than a sheltered one after rain.
How often should you water grass seed?
There is no useful fixed timetable for every lawn. Feel the surface and look for drying, especially in exposed areas and along edges. If it needs water, apply it gently and evenly until the seedbed is damp, without leaving puddles or runoff. In warm or windy weather it may need checking more than once a day; after sustained rain it may need no extra water.
The RHS recommends watering newly sown lawns gently when rain is absent and using a rose or gentle spray for seedlings. A strong jet can dislodge seed, particularly on a slope.
Can you overwater grass seed?
Yes. Standing water and runoff are signs to stop. If the ground stays saturated after rain, allow it to drain rather than watering again. Pay particular attention to low spots, where water can collect even when the rest of the lawn looks dry.
After the seedlings appear
Keep checking moisture as the grass establishes and follow the seed supplier’s aftercare instructions. The RHS notes that repaired areas can dry out until well rooted and may need water when rainfall is insufficient over the following months. Keep people and pets off the young lawn where possible, especially when the soil is soft.
When the grass is ready, see our guide to the first cut of new grass. Allow the surface to firm up before taking a mower onto it.
Plan watering before you sow
If you cannot water during dry spells, or local restrictions prevent it, wait for a suitable opportunity. Our guide to when to sow grass seed covers the usual UK seasons and the weather conditions to look for.
For further detail, see the RHS guidance on repairing lawns.