What Time of Year is Best?

Timing can make or break your grass seeding project. Sow at the right moment and you’ll watch your lawn establish quickly with minimal effort. Get it wrong and you’ll be fighting frost damage, drought stress, or weed competition – possibly all three.

The good news is that grass seed is fairly forgiving, and you have a decent window to work with in the UK. But understanding the ideal conditions will save you time, money, and frustration.

The Quick Answer

Best time: Mid-September to mid-October (autumn)

Second best: Late March to May (spring)

Possible but harder: June to August (summer – needs constant watering)

Avoid: December to February (frost kills seedlings)

The key requirement is soil temperature. Grass seed needs a minimum of 8-10°C to germinate. As a rough guide, this means air temperature averaging 10°C or above over a 24-hour period for at least a week or two.

Why Autumn Is Best

If you can only sow once a year, make it autumn. Mid-September to mid-October hits the sweet spot for several reasons:

The soil is still warm. After a summer of sunshine, the ground retains heat well into autumn. This warmth encourages rapid germination – often faster than spring sowing, when the soil is still warming up from winter.

Autumn rain does the watering for you. As the weather turns, rainfall increases while evaporation decreases. Your seedbed stays naturally moist without you having to drag a hose around every day.

Fewer weeds to compete with. Annual weeds are dying back by autumn, and perennial weeds are slowing down. Your grass seedlings face far less competition than they would in spring, when weeds are bursting into growth.

Roots establish before summer stress. Autumn-sown grass spends winter developing a strong root system. When summer arrives – with its heat, drought, and heavy use – your lawn is already well-established and resilient.

The main risk with autumn sowing is leaving it too late. If you’re still sowing in November, the soil may have cooled too much and early frosts could damage young seedlings before they’re established. Aim to have seeds in the ground by mid-October at the latest.

Spring Sowing: The Second Window

If you miss autumn, spring is your next best opportunity. Late March to May works well in most of the UK, though timing varies by region.

In the south: You can often start as early as late March, once the soil has warmed and frost risk has passed.

In the north: Wait until late April or early May. Spring comes later, and the risk of late frosts is higher. Patience pays off – grass seed sown into cold soil just sits there, potentially rotting before it can germinate.

The main challenges with spring sowing are weed competition and the need for watering. Weeds that have been dormant all winter burst into life alongside your grass seed, competing for the same light, water, and nutrients. You’ll need to stay on top of them.

Spring weather can also be unpredictable. A warm spell followed by frost can damage young seedlings. Check the long-range forecast before you sow, and wait if cold weather is predicted.

Summer Sowing: Possible But Harder

You can sow grass seed in summer, but it demands more effort. The soil is warm enough for rapid germination, but keeping it moist is the challenge.

Grass seed must not dry out during germination. In hot weather, this can mean watering lightly two or three times a day – a significant commitment. Miss a day during a heatwave and you could lose the lot.

If summer is your only option, choose a fast-germinating grass seed to minimise the vulnerable period. Water early morning and evening to reduce evaporation. Consider covering the seedbed with horticultural fleece to retain moisture – but use breathable fleece, not polythene, which can cook seeds in high temperatures.

Avoid sowing during heatwaves or drought. If soil temperatures exceed 30°C, seeds can literally cook. Wait for a cooler spell, ideally with some rain forecast.

Winter Sowing: Why It’s Risky

December to February is the danger zone for grass seeding. Soil temperatures drop below the 8°C minimum, so seeds won’t germinate – they’ll just sit in the cold, wet ground.

Worse, if you get a warm spell that triggers germination, the young seedlings are extremely vulnerable to frost. Their shallow roots can’t access water from frozen soil, and ice crystals damage delicate cells. A hard frost can kill an entire batch of seedlings overnight.

If you absolutely must sow in winter, use a specialist winter grass seed formulated with cold-tolerant ryegrass varieties that can germinate at temperatures as low as 5°C. Even then, results are less reliable than spring or autumn sowing.

How to Check Soil Temperature

You don’t necessarily need a soil thermometer (though they’re cheap and useful). As a rule of thumb, if air temperature has been averaging 10°C or above for the past week or two – both day and night – the soil should be warm enough.

Check the weather forecast for the two weeks ahead. You want consistent temperatures without frost predicted. Ideally, you’ll see some rain forecast too – it saves you work and helps seeds establish.

Remember that soil warms and cools more slowly than air. A brief warm spell doesn’t mean the ground is ready, and a cold snap won’t immediately freeze established soil. Look at the trend over several weeks rather than day-to-day variations.

Regional Timing Guide

The UK varies significantly from south to north and west to east. Here’s a rough guide:

South West England: Mildest region. Spring sowing possible from mid-March; autumn sowing can extend into early November.

South East England: Similar to the south west but slightly cooler. Late March for spring; aim to finish by late October in autumn.

Midlands: Wait until early April for spring sowing. Autumn window closes around mid-October.

North of England: Spring sowing from late April; autumn sowing best completed by early October.

Scotland: Most restrictive timing. Late April to May for spring; September to early October for autumn. Higher regions may have even shorter windows.

After You’ve Sown: What to Expect

Once your seed is down, germination typically takes 7-21 days depending on temperature and grass type. Ryegrass is fastest; fescues are slower but more tolerant of shade and drought.

Keep the seedbed consistently moist until grass is at least 5-6cm tall. This is the critical period – letting it dry out now can kill seedlings that have already germinated.

Wait until grass reaches 6-8cm before the first mow, and set your mower high (remove no more than one-third of the blade length). Avoid heavy foot traffic for at least four to six weeks while roots establish.

For detailed preparation advice, see our guide on how to prepare your lawn for seeding. If you’re creating a completely new lawn, our guide to starting a new lawn from seed covers the full process.

Frequently Asked Questions

What soil temperature do grass seeds need to germinate?

Most grass seed needs a minimum soil temperature of 8-10°C to germinate. As a rough guide, this means air temperature averaging 10°C or above over a 24-hour period for at least a week. Specialist winter grass seed can germinate at temperatures as low as 5°C, but standard mixes need warmth to get going.

Can I plant grass seed in winter?

It’s not ideal. Standard grass seed won’t germinate in cold soil, and young seedlings are easily killed by frost. If you must sow in winter, use a specialist winter grass seed containing cold-tolerant ryegrass varieties. Even then, results are less reliable than spring or autumn sowing. December to February is best avoided if possible.

Is autumn or spring better for sowing grass seed?

Autumn (mid-September to mid-October) is generally better. The soil is still warm from summer, autumn rain keeps seeds moist naturally, and there’s less weed competition. Autumn-sown grass also develops strong roots over winter, making it more resilient the following summer. Spring works well too, but you’ll face more weeds and may need to water more.

How long after sowing can I walk on new grass?

Wait until grass is at least 6-8cm tall and has been mowed at least once – typically four to six weeks after germination. Young grass has shallow roots that are easily damaged by foot traffic. Light use is fine once established, but avoid heavy use or sports for the first full growing season.

Should I water grass seed every day?

The goal is to keep the seedbed consistently moist – not waterlogged, but never completely dry. In cool, damp weather this might mean watering every few days or not at all. In warm, dry weather you may need to water lightly two or three times daily. Once grass is established (around 6cm tall), you can reduce watering and let it develop deeper roots.

The Bottom Line

Grass seed timing isn’t complicated, but it does matter. Autumn is your best bet, spring is a solid second choice, summer is possible with extra effort, and winter is best avoided.

Wait for soil temperatures above 8-10°C, check the forecast for the next couple of weeks, and choose a window when you can keep the seedbed moist. Get these basics right and your grass seed will do the rest.

For more seeding guides and lawn care advice, explore all our lawn care resources.

Ready to get started? Browse our grass seed range – we’ve got options for every lawn, from fast-growing patch repair to hard-wearing family mixes.