Short answer: Most established lawns need about 2.5cm (1 inch) of water per week, including rainfall — usually delivered in one or two deep waterings rather than a little every day. Water early in the morning, and let the weather decide: skip watering when rain is forecast.
Watering sounds simple, but it's where most people get their lawn care wrong. Too little and the grass browns; too much and you invite disease and shallow roots. Here's how to get it right.
The golden rule: deep and infrequent
Grass develops deeper, healthier roots when you water deeply but less often. Frequent shallow watering trains roots to stay near the surface, where they dry out fast.
- Aim for 2.5cm of water per week, rain included.
- Split it into one or two sessions, not daily sprinkles.
- Water until the soil is moist 10–15cm down, then let it dry before the next session.
The best time to water
Early morning (before 9am) is ideal. The air is cool, less water evaporates, and the grass dries during the day — which helps prevent fungal disease.
Avoid evening watering when you can: grass that stays wet overnight is more prone to disease.
How to measure how much you're applying
Put a few empty tuna tins or shallow containers on the lawn while you water. When they've collected about 2.5cm, you've applied roughly a week's worth. Time how long that took so you know your sprinkler's rate.
Adjust for weather and season
This is where a fixed schedule fails. Watering needs change constantly:
- Hot, dry, windy spells: water more often.
- Cool, wet, or rainy periods: water less, or not at all.
- Spring and autumn: lawns often need little extra water in the UK.
- Height of summer: the main time you'll need to supplement rainfall.
Tip: If rain is forecast in the next day or two, hold off. Watering right before rain wastes water and money. YardIQ checks your local forecast and tells you whether to water or wait.
Signs you're watering wrong
- Footprints stay visible after you walk across the lawn — a classic early sign the grass needs water.
- Greyish-blue tint and curling blades — drought stress.
- Spongy, always-wet feel or mushrooms — you're overwatering.
New lawns are different
Newly seeded or turfed lawns need light, frequent watering to keep the surface moist until established — the opposite of the deep-and-infrequent rule. Once roots take hold (a few weeks), switch to the standard approach.
Frequently asked questions
How many minutes should I water my lawn?
It depends on your sprinkler, but aim to apply about 2.5cm of water per week. Use the tuna-tin test to time how long your setup takes to deliver that, then split it across one or two sessions.
Should I water my lawn every day?
Usually no. Daily watering encourages shallow roots. Most established lawns do better with one or two deep waterings a week, adjusted for rainfall and heat.
Is it bad to water the lawn at night?
It's not ideal. Grass that stays wet overnight is more vulnerable to fungal disease. Early morning is the best time to water.
How do I know if my lawn needs water?
Walk across it — if your footprints stay visible, the grass is short on water. A greyish tint and curling blades are also signs of drought stress.