How to Water Your Lawn Effectively
To water your lawn effectively, give it roughly 25-38mm (1-1.5 inches) of water per week in one or two deep soaks rather than a daily splash, ideally first thing in the morning. Deep, infrequent watering drives roots down, cuts evaporation and keeps the nutrients in your feed working for you instead of draining away.
Watering sounds like the easiest job in the garden: point the sprinkler, walk away, done. But get the amount or the timing wrong and you can waste water, waste the feed you have paid for, and still end up with a thirsty, stressed lawn. Here is how to water your lawn properly through a UK summer, without watching the water bill climb.
How much water does a lawn actually need?
Aim for about 25-38mm (1-1.5 inches) of water a week, including any rain. The trick most people miss is to water deeply and infrequently rather than little and often. A quick daily sprinkle only wets the surface, where it evaporates and tempts roots to stay shallow. One good soak a week pushes moisture down and encourages deep, drought-resilient roots.
Not sure how much you are putting down? Use the tuna-can test: pop an empty can on the lawn under the sprinkler and keep going until it is full. That is roughly an inch, and it tells you how long your particular sprinkler needs to run. On hard, hydrophobic or sandy soil, water can run straight off or sink past the roots before the grass gets a look in. A granular wetting agent helps water spread evenly and soak into the root zone instead of pooling or running away.
When is the best time of day to water your lawn?
Mornings win. Watering early lets the grass drink before the day's heat, and the surface dries as the sun comes up, so moisture does not sit in the thatch overnight where it can invite disease. Evenings are a fine fallback if mornings do not fit your routine, ideally once temperatures have dropped. The one time to avoid is the middle of a hot, sunny day, when much of the water evaporates before it reaches the roots.
Watering newly sown grass seed
New seed plays by different rules. It has no established root zone yet, so keep the surface consistently moist with a light water twice a day until it germinates, rather than one weekly soak. If you are sowing in the warmer months, our guide on when to sow grass seed, and why summer is the trickiest time walks through the timing.
Can you water your lawn too much?
Yes. Overwatering wastes both water and money: excess water leaches your paid-for nutrients down past the roots, which is especially true on free-draining sandy soils. Soggy ground also encourages shallow roots and disease. The aim is steady, deep moisture, not a permanent bog.
It helps to understand why this matters. Dry grass is dormant grass: in a drought it slows right down to conserve moisture, and grass that is not growing is not feeding, so it never takes up the nutrients you have applied. Weeds, with their deeper roots, often shrug off the dry spell and gain ground. Two things keep your feed working: only ever apply granular fertiliser when you can water it in, and choose a feed with high potassium, which helps the grass plant use the moisture it has more efficiently and stand up to heat and disease.
How do you keep a lawn alive during a hosepipe ban?
Sign up for your local water authority's alerts so you know the moment a hosepipe ban is announced, and take it seriously: ignoring one can land you a fine. Harvest what you can with a water butt or two for the dry weeks, prioritise any newly sown areas, and let an established lawn go gently dormant if it must. A high-potassium summer feed applied before the heat builds gives the grass the best chance of bouncing back green once the rain returns.
MyLawn is Mowd's free DIY lawn app. It looks at your postcode's weather and the season and tells you the single best thing to do next, in plain English, with smart reminders so you water and feed at the right moment, not the wrong one. Take a look at MyLawn.
Related Mowd guides: Essential Lawn Care Calendar for UK Gardeners · When to sow grass seed in summer
For a quick field version of this routine, see our watering your lawn guide.
Frequently asked questions
How long should you water your lawn for?
- There is no fixed time, because it depends on your sprinkler and soil. Instead of timing it, measure it: put an empty tuna can on the lawn and run the sprinkler until it holds about an inch of water. That is one weekly soak. Most lawns need 25-38mm (1-1.5 inches) per week including rain.
Should you water your lawn every day?
- No. Daily watering only wets the surface and encourages shallow roots. One or two deep soaks a week is far better for an established lawn. The exception is newly sown seed, which needs a light water twice a day to keep the surface moist until it germinates.
Should you water the lawn after applying fertiliser?
- Yes. Granular feeds need watering in to release their nutrients, so only apply fertiliser when you can water it in or rain is on the way. Without it, the feed just sits on the surface and cannot do its job.
Is it bad to water your lawn in the evening?
- Mornings are best, but an evening water is a reasonable second choice once the day has cooled. Just avoid leaving the grass soaking wet overnight where you can, as prolonged surface moisture in the thatch can encourage lawn disease.