When To Plant Grass Seed In The UK
Mid-spring and late summer give grass seed the warm damp soil it needs to germinate quickly in a UK garden.
The short answer
The best time to plant grass seed in the UK is March to April or August to September. In mid-spring and late summer the soil is warm and damp, giving seed the conditions it needs to germinate and root before summer heat or winter cold arrives. Sow once temperatures settle at around 8 to 10 degrees, ideally ahead of a fortnight of sunshine with some rain.
Grass seed is cheap and easy to sow, but timing makes more difference than most people expect. Sow in the right month and you'll see green shoots within days. Get it wrong and the seed sits in cold soil, gets eaten by birds or dries out before it can root.
Further down this page we've shared a spring sowing we did on a family member's lawn, with photos from bare soil through to thick new grass. It shows how quickly seed takes off when the conditions are right. If you need a usable lawn sooner than that, our comparison of grass seed vs turf weighs up the faster option.
When Is The Best Time To Plant Grass Seed?
The UK doesn't have the kind of climate that keeps grass growing all year, so when you sow matters. Plant grass seed in mid-spring or late summer, which means between March and April or August and September. That's when the soil is warm and damp, so the seed germinates quickly and has time to root before the weather turns.
Some manufacturers print their own sowing window on the box, so check that as well. Once you've chosen the right grass seed for your lawn, the sections below explain why those months give it the best start.
Why Mid-Spring And Late Summer Work Best
Temperature
Temperature, moisture and daylight all decide how fast seed germinates and how well the seedlings establish, which is why cold, wet winter weather is the wrong time to sow. Once temperatures settle at around 8 to 10 degrees, the seed wakes up without the stress of summer heat. Our guide on how long grass seed takes to grow covers how those conditions affect the timings.
Seed sown in winter doesn't die. Known as dormant seeding, it sits in the soil until spring warms it enough to germinate. The risk is that it washes away or gets eaten in the meantime, so we'd only sow in winter if the packet says that blend is made for it.
Soil Moisture
Spring warmth arrives with regular showers, and in late summer the soil still holds the season's heat as the first autumn rain comes in. Both keep the seedbed damp without you having to water it constantly. In a dry spell, water the seedbed every day using a garden hose on a gentle spray setting so the seed isn't washed away.
Keeping Weeds Out Of A New Seedbed
Weeds compete with young grass for light, water and nutrients, and their leaves shade the seedlings underneath. The problem is that you can't spray a weed killer over a newly sown lawn without harming the grass. Clear the ground thoroughly before sowing, then pull new weeds by hand before they flower. Keep at it and the grass will soon outgrow them.
Aftercare For Newly Sown Grass
Keep the seedbed moist with regular watering until the grass has established, and stay off the sown area so the seedlings aren't disturbed. Lift off any debris that lands on it and pull weeds as they appear. Hold off mowing until the grass reaches 7 to 8 cm, and our guide on when to cut new grass explains how much to take off.
Other Things To Get Right When Sowing
- Soil preparation: Rake the soil to a fine, crumbly texture like breadcrumbs and pick out stones and debris.
- Seed blend: Match the seed to the spot, with a shade-tolerant blend for areas that get little sun.
- Birds: If they start eating the seed, a net or deterrent over the area protects it.
- Weather forecast: Check the two-week forecast before sowing. Sunshine with some rain is ideal. Seed takes up to around 10 days to germinate, so that fortnight is when the weather counts.
Our Spring Grass Seed Case Study
The lawn in these photos belongs to a family member, and the old grass had died back so far that there was more bare soil than lawn. We sowed it in April. The first photo shows the bare ground, and the second shows the seed germinating just 4 days later.
By day 10, new grass had formed across most of the area, and after 14 days we had thick grass. How quickly yours comes through depends on the seed blend and the weather, but a well-timed spring sowing should follow a similar pattern.
As the last photo shows, a few patches didn't take. We overseeded those spots so they caught up with the rest of the lawn. On a tired lawn that needs a bigger renovation, scarifying before you sow helps the seed reach the soil, and our pick of the best lawn scarifiers covers the machines for that job.
Watch Us Do It
Preparation & Research Is Key To The Success of Grass Seed! We've Tested Several To Find The Best!
What People Also Ask Us
Can you plant grass seed in May?
Yes, you can plant grass seed in May, and it germinates quickly in the warm soil. The risk is a dry spell in late May or June, so be ready to water the seedbed every day until the grass has established. Sowing in March or April gives the seed longer to root before the summer heat arrives.
Is October too late to plant grass seed?
October is late for planting grass seed in the UK. The soil cools quickly as autumn goes on, so germination slows and the seedlings have less time to establish before the frosts. August to September is the safer window for an autumn sowing, and anything later is better left until the following spring.
Should you water grass seed every day?
Water grass seed every day in dry weather until it germinates and the seedlings have established. The seedbed needs to stay moist but not waterlogged, so use a gentle spray rather than a strong jet that washes the seed away. In showery spring weather you can skip days when the soil is already damp.
How long does grass seed take to germinate in the UK?
Grass seed sown at the right time of year germinates within about 10 days in the UK, and faster in warm, damp conditions. In our April sowing the first shoots appeared after 4 days and the lawn was thick after 14 days. Cold soil and dry weather both slow germination down.
Is it worth sowing grass seed in winter?
Only if the seed packet says that blend is made for it. Winter-sown seed doesn't die. It sits in the soil until spring warms it enough to germinate, which is known as dormant seeding, and the catch is that it can wash away or get eaten while it waits. A spring or late summer sowing gets the lawn going far sooner.
What happened with the spots that didn't take in your spring sowing?
We overseeded those spots so they caught up with the rest of the lawn. By day 10 new grass had formed across most of the area, and after 14 days we had thick grass with a few bare patches still showing in the last photo. How quickly yours comes through depends on the seed blend and the weather.
How do I stop birds eating grass seed?
Put a net or a deterrent over the sown area. Seed that sits on the surface gets eaten by birds, which is one of the things that goes wrong with a poorly timed sowing. Sown at the right time, the seed germinates within days, so it isn't left on show for long.
Can I spray weed killer on a newly sown lawn?
No. Weed killer harms the new grass as well as the weeds, so do the clearing before you sow and pull any newcomers by hand before they flower. Stay on top of them for the first few weeks, because they steal light, water and nutrients from the seedlings, and the grass will soon outgrow them.
Archie is our gardening specialist. He started out as an apprentice at a gardening firm, built up his own knowledge from there and now writes most of our garden content.