Growing tomatoes outdoors in Britain is entirely possible — gardeners do it every year and eat well from it — but it is a race. The frost-free season is short, summer warmth is not guaranteed, and late blight lurks in every damp August. Success comes from choosing the right varieties, starting on time, and giving plants the sunniest, most sheltered spot you own.
Honest framing: what you are up against
Tomatoes (Solanum lycopersicum) are tender plants, hardiness rating H1C — they tolerate no frost at all and sulk below about 10°C. Outdoors in most of the UK that gives you a growing window from late May to late September: roughly four months to go from planted-out seedling to ripe fruit. The second constraint is late blight (Phytophthora infestans), a wind- and rain-borne disease that can destroy outdoor tomatoes within a week or two once it strikes, typically from July onwards in warm, wet spells.
Both constraints point to the same strategy: grow early-maturing and blight-resistant varieties, and get fruit set as soon as the season allows. Cherry tomatoes ripen faster than beefsteaks and are much the safer outdoor bet. Varieties bred with strong blight resistance — the Crimson series ('Crimson Crush' and its siblings), 'Mountain Magic' and 'Losetto' among them — have transformed outdoor growing, and if blight has ruined your crops before, they are worth the premium on seed. Traditional favourites such as 'Gardener's Delight' remain excellent in a dry year, but they carry no blight protection.
Cordon or bush?
Tomato varieties come in two habits, and everything about training the plant follows from which you have — check the packet.
- Cordon (indeterminate) varieties grow as a single tall stem tied to a cane, with side shoots removed. Most classic varieties are cordons. They make the most of a small footprint but need weekly attention.
- Bush (determinate) varieties stop growing at a natural height and sprawl. No side-shooting or stopping is required — you just support them loosely and let them get on with it. For outdoor growing, containers and hanging baskets ('Tumbler', 'Losetto'), bush types are the low-maintenance choice.
Sowing indoors, March to April
Outdoor tomatoes need a head start under cover. Sow from mid-March to mid-April — for most gardens late March is the sweet spot. Sown much earlier, plants become leggy and root-bound waiting for the frosts to end; much later, and ripening runs into autumn.
- Sow seed 1cm deep in pots or modules of seed compost, and keep at 18–21°C — a windowsill above a radiator or a heated propagator both work. Germination takes one to two weeks.
- Once seedlings show their first true leaves, prick out into 9cm pots and grow on in the brightest, coolest bright spot you have (around 15–18°C), turning pots regularly so plants stay straight.
- Pot on again if roots fill the pot before planting-out time. A good plant for late May is 20–30cm tall, stocky and dark green, ideally with the first flower truss just showing.
No windowsill space? Garden centres sell young plants from April; buy stocky ones in May rather than tall, pale ones in April.
Hardening off and planting out
Plant out only after your last frost — late May in much of southern England, early to mid-June further north and in frost pockets. Harden plants off first: a week to ten days of standing them outside by day and bringing them in at night, then a few nights out under fleece, toughens the growth so cold winds do not check it.
Give each plant the sunniest, most sheltered position available — a south- or west-facing wall or fence is genuinely worth degrees of warmth and reflects heat back in the evening. Space plants about 45–60cm apart in soil enriched with garden compost, or one plant per 30cm (10-litre-plus) container, or two to three per growbag. Bury the stem a little deeper than it grew in the pot; tomatoes root along the buried stem. Push in a 1.5m cane for cordons at planting time, not later when it would spear the roots.
Watering: consistency beats quantity
More outdoor tomato problems come from erratic watering than from anything except blight, and two disorders tell the story on the fruit itself:
- Blossom end rot — a sunken, leathery black patch on the base of the fruit — is a calcium-transport problem caused by the compost drying out, not a disease and not usually a soil deficiency. Container plants are most at risk.
- Split fruit happens when a dry spell is followed by heavy watering or rain: the flesh swells faster than the skin can stretch.
The fix for both is the same: steady moisture. Plants in the ground may need a thorough soak two or three times a week in summer; containers and growbags often need watering daily, morning by preference. Water the soil, not the foliage — wet leaves invite blight. A mulch of compost around plants in open ground evens out moisture and cuts the workload.
Feeding, side shoots and stopping
Feeding
Start feeding weekly with a high-potash liquid tomato feed once the first truss has set fruit — usually late June or July outdoors. Feeding earlier, or with a nitrogen-rich general feed, produces lush leaves at the expense of fruit. Plants in good garden soil need less feeding than those in containers, which depend on you entirely.
Pinching out side shoots (cordons only)
Every week, snap out the shoots that sprout in the angle between each leaf and the main stem, while they are small enough to remove with finger and thumb. Left alone they turn the plant into an unproductive thicket. Tie the main stem to its cane as it climbs. Bush varieties: leave them entirely alone.
Stopping the plant
Outdoors, fruit that sets after mid-August will rarely ripen before the season ends. So in early to mid-August, cut the top out of each cordon two leaves above the fourth or fifth truss. The plant then puts its remaining energy into swelling and ripening what it has. Removing a few lower leaves below the bottom truss at the same time improves airflow and lets sun reach the fruit.
Blight: recognising it and responding
Late blight arrives on warm, humid air, typically July to September, and moves fast. Know the signs:
- Brown-black patches on leaves, often at the edges, sometimes with a pale halo and a fuzzy white bloom underneath in damp weather
- Dark brown streaks on stems
- Firm, chocolate-brown blotches spreading on green and ripening fruit
There are no fungicides available to home gardeners for tomato blight, so the response is managerial. At the first confirmed signs on a non-resistant variety, strip and dispose of affected foliage; if stems are streaked, the game is usually up — pick every fruit of decent size immediately (healthy green ones will ripen indoors; blotched ones will not) and remove the plants. Do not compost blighted material in a cold heap; use the council green waste collection or bury it deeply. Resistant varieties will usually shrug off the same conditions with minor leaf spotting, which is exactly why they are worth growing.
Prevention helps at the margins: water at the base, keep foliage dry, space plants for airflow, and grow well away from any potatoes, which share the disease.
Ripening the last of the crop
Come late September, outdoor plants will still carry green fruit that is not going to ripen where it hangs. Pick everything before the first frost. Tomatoes ripen through their own ethylene, not sunlight, so a windowsill is unnecessary — a drawer or paper bag at room temperature works better, and adding a ripe banana speeds things up by supplying extra ethylene. Full-sized green fruit will colour over one to three weeks; check regularly and remove anything that softens or spots. Any that stubbornly refuse make excellent green tomato chutney, which is the traditional and entirely honourable end to a British tomato season.