When to Plant Tomatoes in the UK
Timing is the thing people most often get wrong with tomatoes. Sow too early and you spend six weeks nursing a leggy plant on a windowsill that can’t go outside. Sow too late and the fruit is still green when the frosts arrive. What’s right depends on two things: whether the plant will end up under glass or out in the open, and whereabouts in the country you are.
Quick answer
For plants that will live under glass, sow between late February and the middle of March; for anything going outdoors, hold off until the last week of March or the start of April. Plant greenhouse tomatoes out from late April or May, and outdoor plants only once the last frost has passed and nights stay above about 10°C, which runs from mid-May in the south-west to mid-June in northern Scotland.
Sowing calendar
Late February to mid-March: sow for greenhouse growing
Late March to early April: sow for growing outdoors
Mid-April onwards: the last useful sowings, and best kept to quick cherry varieties
Seed wants about 18°C before it will come up, which means a propagator or a bag over the pot on the warmest sill you have. Count roughly six to eight weeks from sowing to a plant that’s ready to go out.
The reason outdoor tomatoes are sown later is simple arithmetic: there’s no point having a large plant ready in April when it can’t safely be planted until late May.
When to plant out: greenhouse
Greenhouse and polytunnel tomatoes can go into their final position from late April into May, once the structure is holding reasonable warmth overnight. An unheated greenhouse gives you roughly a month’s head start on the open garden; a heated one, more.
This earlier start is the main reason greenhouse tomatoes crop sooner and keep going later into autumn.
When to plant out: outdoors
Tomatoes are tender and will be killed by frost, but frost isn’t the only thing to wait for. Cold nights above freezing still check growth badly, so the target is nights consistently above about 10°C rather than simply the absence of frost.
Typical timings:
Mid to late May: the south coast and the south-west
The second half of May: south Wales and the rest of southern England
The very end of May: the Midlands, Yorkshire, the north-west and north Wales
Early June: north-east England, Northern Ireland and the south of Scotland
Mid-June: the Highlands and the far north of Scotland
Adjust for your own garden. A sheltered town or coastal plot can often go a week or two earlier, while an exposed site, high ground or a known frost pocket wants an extra one to three weeks.
Hardening off
Whatever the date, plants raised indoors can’t go straight outside. Allow two or three weeks to accustom them, putting them out during the day and back in before dark, and lengthening the stint outside each time. Skipping this stalls plants for weeks or scorches the leaves outright.
Our hardening off guide sets out the routine.
If a cold snap catches you out
Late frosts happen, and a forecast can turn within a few days of planting. Keep fleece within reach through late spring and cover plants overnight when cold is forecast, doubling it up if the night looks severe. Pots can simply be moved back under cover.
Is it too late to plant tomatoes?
Sowings up to about mid-April still crop, especially fast cherry varieties, though they’ll be later and the harvest shorter. After that, buying young plants in May is the sensible route, and garden centres sell them precisely because so many people start late.
By June, outdoor sowing isn’t worth it, but a bought plant going into a greenhouse can still produce a worthwhile crop before autumn.
What happens if you plant too early
This is the more common mistake. Tomatoes put outside into cold soil sit and sulk, turn purplish or yellow, and stop growing. A plant held back indoors for an extra fortnight and planted into warm soil will usually overtake one that went out early and was checked.
Plants left too long in small pots run into the opposite problem, becoming pot-bound and stressed. If planting out is delayed by weather, move them into larger pots rather than letting them sit.
After planting
Once the plants are in the ground, our main guide to growing tomatoes in the UK takes over: support, side shoots, feeding and picking. Patio growers want tomatoes in containers, and there’s a month-by-month greenhouse guide for the year under glass.
Looking at the whole plot rather than one crop? Try starting vegetable seeds indoors and our planting calendar for the UK
Common questions
When do I need to sow if I want to plant out in late May?
Count back six to eight weeks, which puts the sowing in late March or early April. Greenhouse plants are sown earlier, from late February, because they go into their final position sooner.
When can tomatoes go outside in the UK?
After the last frost, once nights stay above roughly 10°C. That’s mid to late May in the south-west, the end of May across much of England and Wales, and early to mid-June in Scotland.
Can I plant tomatoes in April?
In a greenhouse, yes, from late April. Outdoors, no: April nights are far too cold in all but the mildest, most sheltered spots.
Is it too late to plant tomatoes in June?
Too late to sow outdoors, but a bought plant put into a greenhouse in early June can still crop before autumn.
How long do tomatoes take from seed to planting out?
About six to eight weeks, which is why the sowing date needs to be worked backwards from when it’s safe to plant out in your area.
Sowing temperatures, planting-out timings and regional dates based on RHS guidance.