How & When to Water your Lawn

Here in the UK, we’re blessed with enough rainfall that most lawns rarely need watering. But when summer brings a dry spell – or when you’re trying to establish new grass seed – knowing how and when to water makes all the difference.

Get it right and your lawn stays green while the neighbours’ turns brown. Get it wrong and you’ll waste water, encourage disease, or watch your expensive grass seed fail to germinate.

Do You Actually Need to Water Your Lawn?

For established lawns, the honest answer is: probably not as much as you think.

British lawns are remarkably resilient. During dry spells, grass naturally goes dormant – turning yellow or brown to conserve energy. It looks dead, but it isn’t. The crown and roots stay alive, and the lawn will green up again when rain returns. A healthy lawn can survive 4-6 weeks of drought without suffering permanent damage.

So if you’re happy to let your lawn go a bit straw-coloured during a heatwave, that’s absolutely fine. It will recover.

However, there are times when watering is essential: when you’ve just sown grass seed, when you’ve laid new turf, or when you simply want to keep your lawn looking green through summer.

The Best Time of Day to Water

Early morning (5am-10am) is ideal. The air is cool, wind is usually calm, and water has time to soak into the soil before the heat of the day causes evaporation. The grass blades also dry quickly once the sun comes up, which is important for preventing disease.

Early evening (4pm-6pm) is the second-best option. Temperatures are cooling but there’s still enough warmth and daylight for the grass to dry before nightfall.

Avoid watering in the middle of the day. Most of your water will evaporate before it reaches the roots – you’re essentially watering the air. It’s wasteful and ineffective.

Avoid watering late at night. If grass stays wet overnight, you’re creating perfect conditions for fungal diseases like red thread and fusarium. These thrive in cool, damp conditions and can damage your lawn far more than a bit of drought stress.

How Much Water Does Your Lawn Need?

A lawn needs about 25mm (1 inch) of water per week during dry weather, including any rainfall. This is enough to soak the soil to a depth of 15-20cm, encouraging deep root growth.

The key principle: water deeply but infrequently.

One thorough soaking once or twice a week is far better than a light sprinkle every day. Deep watering encourages roots to grow downwards in search of moisture, making your lawn more drought-tolerant. Shallow daily watering keeps roots near the surface where they’re vulnerable to drying out.

How do you know if you’ve watered enough? Push a screwdriver or garden fork into the soil after watering. It should slide in easily to a depth of 15cm or so. If the soil is hard and resistant, water hasn’t penetrated deeply enough.

Signs Your Lawn Needs Watering

The bounce-back test. Walk across your lawn and look back. If the grass springs back up, it’s fine. If your footprints stay visible for more than a few seconds, the grass is stressed and needs water.

Colour change. Grass turns from bright green to a dull blue-grey or straw colour when it’s short of water. This is the plant going into survival mode.

Soil check. Dig a small hole about 15cm deep. If the soil is dusty and falls away from the roots easily, it’s time to water.

Curling blades. Grass blades will fold or curl inwards to reduce their surface area and conserve moisture. This is an early warning sign before colour changes.

Watering New Grass Seed

New grass seed is a completely different situation. Seeds need consistent moisture to germinate – if they dry out, they die. There’s no coming back from that.

Keep the top 3-4cm of soil consistently moist (not waterlogged) until germination. This usually means watering once or twice daily, depending on the weather. Morning and late afternoon is ideal.

Use a fine spray. A watering can with a rose attachment or a hose with a gentle spray setting. Heavy water flow will displace seeds and create bare patches.

Watch the weather. On hot, windy days you may need to water more frequently. On cool, overcast days, once may be enough. The goal is consistent moisture, not flooding.

Reduce frequency after germination. Once the grass is up and growing (usually 7-14 days after sowing), gradually reduce watering frequency but increase the amount. This encourages the young roots to grow deeper. After the first few mows, you can treat it like an established lawn.

If you’re sowing seed in summer, be prepared to water religiously. Dry conditions are the number one reason grass seed fails. For easier establishment, consider sowing in spring or autumn when rainfall is more reliable.

Watering Methods Compared

Sprinklers are convenient for large lawns. Set them up, turn them on, and do something else while they work. Oscillating sprinklers cover rectangular areas well; rotating sprinklers suit circular coverage. The downside: they can be wasteful if not positioned carefully, watering paths and patios as well as grass.

Hose with spray attachment gives you control over exactly where water goes. Use a gentle spray setting to mimic rainfall. Good for targeting specific areas or watering new seed, but time-consuming for large lawns.

Watering can is perfectly adequate for small lawns or spot-watering dry patches. Always use a rose attachment for even distribution. The exercise is free.

Tip: Rainwater is actually better for your lawn than tap water. It contains nitrogen and is naturally soft. If you have water butts, use them for the lawn first.

Hosepipe Bans

During prolonged droughts, water companies may impose hosepipe bans. These typically prohibit using a hosepipe or sprinkler on gardens, though watering cans filled from a tap are usually still allowed.

If a ban is in place, remember that your established lawn will survive. Focus any permitted watering on newly seeded areas or recently laid turf – these genuinely need moisture to survive. Let the rest of the lawn go dormant; it will recover when restrictions lift and rain returns.

Preparing Your Lawn for Dry Weather

A few practices help your lawn cope better with drought:

Mow higher. Raise your mower to 4-5cm during dry spells. Longer grass shades the soil, reducing evaporation and keeping roots cooler.

Leave clippings on the lawn. They act as a mulch, helping retain moisture and returning nutrients to the soil.

Aerate in autumn. Compacted soil prevents water from penetrating to the roots. Aerating with a garden fork or hollow-tine aerator improves water absorption.

Don’t fertilise during drought. Fertiliser stimulates growth, which increases water demand. Wait until rain returns or you can water regularly.

Choose drought-tolerant seed. If you’re overseeding or starting a new lawn, fescue varieties are more drought-tolerant than ryegrass. Make sure to prepare your soil properly before sowing for best results.

For a complete guide to keeping your lawn in shape during the warmer months, see our summer lawn care guide.

Frequently Asked Questions

What’s the best time of day to water grass?

Early morning, between 5am and 10am. Water soaks into the soil before the heat causes evaporation, and grass blades dry quickly, reducing disease risk. Early evening (4-6pm) is second best. Avoid midday (wasteful) and late night (encourages fungal disease).

How often should I water my lawn?

During dry weather, water deeply once or twice a week rather than little and often. Aim for about 25mm (1 inch) of water per week including rainfall. Deep, infrequent watering encourages roots to grow deeper, making your lawn more drought-tolerant.

Should I water new grass seed every day?

Yes, usually once or twice daily until germination (7-14 days). The top few centimetres of soil need to stay consistently moist – not waterlogged, but never completely dry. After the grass is established and mowed a few times, gradually reduce to normal watering.

Can I let my lawn go brown in summer?

Absolutely. Brown grass isn’t dead grass – it’s dormant. UK lawns can survive 4-6 weeks of drought. The grass will green up naturally when rain returns. If you’d rather keep it green, water deeply once a week during dry spells.

What are signs my lawn needs watering?

Footprints that stay visible (grass doesn’t bounce back), colour changing from green to blue-grey or straw, and soil that’s dry and dusty when you dig down 15cm. Grass blades may also curl inwards to conserve moisture.

The Bottom Line

Most established UK lawns need far less watering than people think. Let your grass go dormant during dry spells if you’re happy with that – it will recover. If you want to keep it green, water deeply once a week, early in the morning.

The exception is new grass seed, which needs consistent moisture to germinate. Water little and often until it’s up and growing, then gradually transition to the deep-and-infrequent approach.

For year-round guidance on keeping your lawn in top shape, check out our complete lawn care guide.