When does grass start growing in the UK?

Grass in the UK starts growing again when the soil holds above about 6C. Meaningful growth begins at that soil temperature, and it is the only start signal the plant answers to. The calendar date it happens on moves by weeks between years and by a fortnight or more between the south coast and the north of Scotland.

Teagasc puts the onset of meaningful grass growth at about 6C soil temperature. That figure comes from grassland agriculture rather than lawns, and sources put the threshold anywhere in a band of about 5 to 6C. We use 6C as the parameter in our own model, and the /method page explains what that assumes and where the model measures it.

So the honest answer to “when does grass start growing in the UK” is a temperature, not a date. But a temperature is only useful if you know yours.

The soil temperature that starts growth

Two things about that 6C figure are worth knowing before you act on it.

It is a soil temperature, not an air temperature. Soil warms more slowly than air in spring and holds its heat longer in autumn, so a mild week in February can leave the soil still under the threshold. This is why a warm spell that brings the daffodils out rarely brings the lawn with it.

And it is measured in the soil, at depth, not on the surface. The exact depth varies between sources: our model works at 6cm, some agronomy references work at 10cm, and a reading taken at one depth is not the same number as a reading taken at another. A probe pushed to about 6cm under the turf gives you a figure you can compare with ours. How soil temperature is measured covers the practical side.

Once the soil passes the threshold, growth starts slowly and accelerates as the soil keeps warming. The first fortnight of growth is not lawn-mowing weather yet. It is the lawn getting going.

Why the calendar date misleads

Spring does not arrive on a fixed date. The JNCC’s Spring Index, which tracks the timing of spring across the UK, shows it shifting by days to weeks between years; 2011 was the earliest spring in the series. The same lawn in the same garden can start growing in early March one year and in early April the next, and nothing the gardener did caused the difference.

Geography moves the date too. In a mild south-west winter grass may barely stop growing, while in north-east Scotland growth effectively stops for around two months. Those two gardens are living in different growing seasons while sharing a calendar.

This is the problem with month-based lawn advice in general, and why calendar lawn advice is wrong takes it apart in full. March is a description of the average year. Your lawn is not living in the average year.

How to tell it has started on your lawn

You do not need a thermometer to see the threshold being crossed, though a thermometer tells you sooner. Three signs are enough:

• The grass colour lifts from winter olive to a brighter green, and blades stand up rather than lying flat.
• The surface dries enough to walk on without marking, and the mower will not sink in.
• Growth shows as height. When you can see the lawn has visibly grown since you last looked, it is growing.

That last one is also the rule for the first cut: the trigger is growth, not the date. When growth has clearly started, mow lightly and high, about 40mm or simply the mower’s highest setting. The RHS mowing guide’s advice for the first cut of the year is the same, and the full version is in when to cut grass after winter. Taking the lawn down to summer height in one go is the most common way to set a lawn back in March.

What temperature does grass stop growing at

Searchers ask the start and the stop question together, so: around the same range. The mowdar model uses the same 6C soil-temperature parameter in both directions, as soil cools back through the threshold in autumn. What that means for the last cut of the year is in when to stop mowing in autumn.

The same seasonal spread applies in reverse. Growth can persist through a mild winter in the south-west and stop for months in the north-east, and the autumn dates move year to year exactly as the spring ones do.

Where your lawn is right now

The threshold is a single number, but the date your lawn crosses it is local and annual. That is the part we built mowdar to answer.

For any UK or Ireland location we model soil temperature at 6cm, growth potential on the PACE Turf framework, and the 10-day mow forecast behind it, with a confidence figure from a 94-run ensemble. So instead of a national rule of thumb you get your own answer: whether your soil has reached the threshold yet, when it is forecast to, and how confident the forecast is. The soil temperature page is the direct lookup, and the mow forecast puts it to work.

What to do once it starts

The first month of the growing season has a short list.

Mow once, lightly and high, as soon as growth is clear. Then let the lawn get ahead of you rather than cutting it back to summer height early. Feed only once growth is well underway, and only if the lawn needs it, which is the RHS position and the subject of when to apply spring lawn feed. Spring seeding waits for soil temperature as well, because grass seed germinates on its own thresholds; how long grass seed takes to germinate has the species numbers. The whole sequence, month by month, is in the spring lawn care guide.

FAQ

How do I measure my lawn’s soil temperature? Push a soil thermometer into the turf to about 6cm and read it in the morning, ideally in a spot that represents the lawn rather than the sunniest corner. Once a week is enough for garden decisions. How soil temperature is measured goes through the details, or the modelled figure on our soil temperature page does the work for you.

Does grass grow in winter in the UK? In places, yes. In a mild south-west winter grass may barely stop growing, while in north-east Scotland growth effectively stops for around two months. Most of the UK sits between those poles: growth slows to almost nothing through the coldest weeks and restarts whenever the soil warms back through about 6C.

When should I mow the lawn for the first time? When growth has clearly started, not on a calendar date. Cut lightly and high, about 40mm or the mower’s highest setting, and only take off the top. The first cut of the year is a tidy-up that lets light to the base; it is not the cut that sets summer height.

Is it too early to feed the lawn in February? Usually. Soluble nitrogen applied before growth starts largely washes through the soil and out of the root zone. Wait until growth is well underway, and feed only if the lawn needs it. The full timing logic is in when to apply spring lawn feed.

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The start of the growing season is a soil temperature, and soil temperature is a local number. Check the modelled soil temperature for your location and the mow forecast to see whether your lawn has crossed it.