How to grow tomatoes in the UK — complete RHS-aligned guide

How to grow tomatoes in the UK — complete RHS-aligned guide

Tomatoes are the UK's most-grown edible — and the one most likely to disappoint a beginner. The two killers in British conditions: planting out too early (a late frost wipes out a season's seedlings in one night) and blight (the wet UK summer makes Phytophthora infestans almost inevitable outdoors after July). This guide is the full year-one UK playbook: indoor sowing timing, transplant, training, feeding with British products, and the problems that will probably hit your plants.

Track your tomato plants: Add your variety to Growli and the app sets reminders tied to your UK region — when to sow, when to harden off, when to plant out, when to start Tomorite, and when blight pressure is high in your area.

US gardeners — see the US version of this guide for zone-based context.

When to plant tomatoes (UK regions)

Tomatoes are tender — they cannot tolerate frost or cold compost. The UK has a short growing season, so timing matters more than in warmer climates. Approximate dates:

These are averages — check the UK hardiness ratings and your local Met Office forecast for the final two weeks of May. The general rule: do not plant out until night temperatures reliably stay above 10°C.

Choose varieties before you choose plants

Cordon vs bush

• Cordon (indeterminate) — trained as a single stem up a cane or string, side shoots pinched out. Higher yields, longer season, best for greenhouses. Examples: Sungold, Gardener's Delight, Alicante, Shirley, Sweet Million, Moneymaker.
• Bush (determinate) — left to sprawl, no pinching, produces all fruit in a 2-3 week window. Good for outdoor containers, hanging baskets, and beginners. Examples: Tumbling Tom, Maskotka, Red Alert, Roma VF.

Beginner UK varieties

• Gardener's Delight — the UK classic; small red, prolific, dependable. Cordon.
• Sungold F1 — orange cherry, exceptionally sweet, cordon, very reliable.
• Shirley F1 — disease-resistant medium-sized red, cordon, the standard greenhouse variety.
• Sweet Million F1 — heavy-cropping cherry, cordon, blight-resistant.
• Tumbling Tom — bush variety bred for baskets and patio pots, fully hardy outdoors in southern England.
• Crimson Crush F1 — the blight-resistant tomato; if you grow outdoors, start here. Cordon.
• Mountain Magic F1 — another excellent blight-resistant cordon.

Avoid heritage Italian beefsteaks (San Marzano, Costoluto Fiorentino) in year one — they are gorgeous but need consistent heat the UK rarely provides outdoors. Save them for a heated greenhouse year.

Where to grow tomatoes in the UK

Three options, ranked by ease:

1. Greenhouse or polytunnel — best. Adds 2-3°C, blocks rain that spreads blight, extends season by 4-6 weeks. Even a £40 plastic greenhouse from Wickes or B&Q transforms a small garden.
2. South-facing wall or fence outdoors — second best. The wall absorbs heat by day and releases it at night. Train against the wall for shelter and reflected warmth.
3. Open ground or exposed patio — only with blight-resistant varieties (Crimson Crush, Mountain Magic) and only south of Birmingham. North of the Midlands, outdoor tomatoes are a gamble.

Soil and compost

Tomatoes need:

• Full sun — 6+ hours direct. In UK conditions, more is better.
• Well-draining, moisture-retentive compost with plenty of organic matter.
• Slightly acidic pH — 6.0-6.8 ideal.
• Calcium — prevents blossom end rot. A handful of crushed eggshells or 1 tablespoon of garden lime per planting hole.

Container and grow-bag growers: use a quality multipurpose compost (Westland John Innes No. 3, Levington Tomorite Giant Planter, or any peat-free multipurpose). Garden soil alone compacts in containers and suffocates roots.

UK grow-bag tip: standard grow bags are very shallow. Cut two large holes in the top, push the bag into a deep tray, and water through the tray to keep the lower compost moist. Or use the bag as a base and stand a bottomless pot ("ring culture") on top of it for deeper rooting.

Transplanting — the right way

1. Harden off indoor-started seedlings over 7-10 days from early to mid-May. Set them outside in a sheltered spot during the day, bring them in at night for the first week, then leave them out overnight once nights reliably stay above 10°C.
2. Plant deep. Bury the stem so only the top 2-3 sets of leaves are above compost. Tomato stems form roots wherever buried — deep planting gives a stronger root system, vital in the UK's short season.
3. Spacing — 45-60 cm apart for cordon, 60-90 cm for bush.
4. Add support immediately — bamboo cane or string for cordon, low ring for bush. Adding support later damages roots.
5. Water deeply after planting. Then resume normal schedule.

Watering

The single most important variable in UK tomato production. The pattern:

• Deep watering 2-3 times per week — not light daily watering.
• At the base, not on leaves — wet leaves invite blight and other fungal diseases, the bigger UK risk.
• Consistent — inconsistent watering causes blossom end rot, cracking, and split fruit.
• More in greenhouses on hot days — over 25°C, plants may need water daily; over 30°C, twice daily.

Mulch heavily (3-5 cm of straw, grass clippings, or composted bark) outdoors to retain soil moisture and stabilise root temperature.

Feeding the UK way — Tomorite and friends

Tomorite (Levington) is the UK gold-standard tomato feed — high-potassium, widely available, and easy to dose — but it is not the only good option; our full comparison of what fertiliser for tomatoes works in the UK weighs Tomorite against granular and organic alternatives. The schedule:

1. At planting: A handful of pelleted chicken manure or a sprinkle of blood, fish and bone mixed into the planting hole.
2. From first flowering: Tomorite or any high-potassium tomato feed at the bottle-recommended dilution, once a week.
3. Through fruiting: Continue weekly Tomorite. Increase to twice a week during peak cropping in July-August if plants are heavy-cropping.
4. Stop: 2 weeks before the final harvest in September-October.

Alternatives: Westland Tomato Food, Vitax Liquid Tomato Feed, Maxicrop Seaweed Plus Tomato. Organic option: comfrey tea brewed from leaves grown at the allotment.

Pruning and training

Cordon varieties

Remove "side shoots" — the small shoots that grow in the V between the main stem and side branches. Pinch them out weekly while they are small (under 5 cm). Tie the main stem to the cane or twist around the string every 30 cm of growth.

When the plant reaches the top of the greenhouse or 5-6 trusses (flower clusters) outdoors, pinch out the growing tip ("stopping" the plant) to direct energy into ripening existing fruit before the season ends. UK rule of thumb: stop cordon plants by mid-August outdoors, mid-September in the greenhouse.

Bush varieties

Do not pinch the side shoots — bush tomatoes set fruit on those side branches. Just provide low support and let them sprawl.

Removing lower leaves

Once the first truss has set fruit, remove the bottom leaves below it. Then remove leaves below each truss as fruit ripens. This:

• Reduces blight transmission from soil splash — the biggest UK benefit.
• Improves air circulation in the dense greenhouse environment.
• Ripens fruit faster as more light reaches it.

When to harvest

Pick when the fruit is fully coloured but still slightly firm. From August onwards in the UK, pick at the first hint of pink or orange — finish ripening on a sunny windowsill indoors. This protects against the inevitable blight strike and saves the harvest if you get a cold, wet week.

Indoor ripening: tomatoes ripen on the kitchen counter at 18-21°C. Do not refrigerate ripe tomatoes — cold destroys flavour compounds.

The 5 problems UK growers face

1. Late blight (Phytophthora infestans) — the big one

Brown patches on leaves, black streaks on stems, brown-black patches on fruit that rot from within days. Almost inevitable on outdoor tomatoes from mid-July onwards in wet UK summers — and it spreads from potato fields, so allotment growers are at higher risk.

Prevention:

• Grow under cover (greenhouse, polytunnel, cloche).
• Grow blight-resistant varieties (Crimson Crush, Mountain Magic, Crimson Plum).
• Remove lower leaves to keep foliage off the soil.
• Water at the base, never on leaves.
• Sign up to Blightwatch.co.uk for free Smith Period (high-risk) email alerts.

Treatment: Once blight strikes outdoors, there is no fungicide approved for home gardeners that will cure it. Pull and bin affected plants (do not compost). Pick any unaffected fruit immediately to ripen indoors.

2. Blossom end rot

Black sunken patch on the bottom of fruit. Cause: calcium uptake failure, almost always from inconsistent watering — extremely common in grow bags and containers that dry out between waterings. Fix: mulch + deep regular watering. The eggshell or lime added at planting helps prevent it.

3. Cracking and splitting

Concentric cracks around the stem end. Cause: heavy watering after a dry spell. Fix: consistent watering, mulch. Pick affected fruit early — they spoil fast.

4. Yellowing lower leaves

Either overwatering or magnesium deficiency. See why are my plant leaves turning yellow in the UK and the Epsom salts fix. Particularly common in grow bags by mid-season as the compost depletes.

5. No fruit set despite flowers

Caused by extreme heat (over 30°C suppresses pollination — yes, this happens in UK heatwaves) or lack of pollinators in closed greenhouses. Open greenhouse doors and vents on warm days, gently tap or shake plants daily to release pollen, and grow companion flowers (calendula, basil, marigolds) nearby to attract bumblebees. The same warm sheltered spot that suits tomatoes also suits UK peppers, and a pot of basil grown the British way doubles as both companion planting and a kitchen crop.

Greenhouse-specific UK advice

• Ventilate aggressively. Open doors and roof vents every morning by 9 am, close again by 5 pm. Stagnant humid air is blight's friend.
• Whitewash or shade the glass in July-August. Greenhouse temperatures can hit 40°C+ in a UK heatwave, halting fruit set.
• Damp down the floor on hot days — wets the concrete or paving and cools the greenhouse by evaporation.
• Companion plant with basil and French marigolds to deter whitefly, a chronic greenhouse pest.

How many plants per UK household

A rough guide for British summer cropping:

• 2-3 plants — fresh eating for a couple, summer salads
• 4-6 plants — fresh eating for a family of 4
• 8-12 plants — fresh eating + some sauces and chutneys
• 20+ plants — serious bottling, freezing and preserving for the winter

Cordon varieties produce 2-3 times the seasonal yield of bush varieties. Mix one or two of each, and always include at least one blight-resistant cultivar.

Related articles

• Why are my plant leaves turning yellow? UK guide — magnesium and overwatering on tomatoes
• How to get rid of fungus gnats in the UK — common in propagator trays
• UK hardiness ratings & last-frost dates — for timing transplants
• How often to water succulents — UK — for the rest of your growing setup

Reviewed and updated by the Growli editorial team. For questions about anything here, open Growli and ask — or email hello@getgrowli.app.