How to Grow Tomatoes in a Greenhouse UK: The Practical Year Round Guide

The six decisions that determine your tomato harvest

Before any seed touches compost, decide:

1. Variety type — cordon (indeterminate, vertical) OR bush (determinate, sprawling)
2. Variety choice — by tomato type (cherry, beefsteak, plum, classic round) and disease resistance
3. Sowing date — late February to mid-March in UK greenhouse
4. Growing medium — soil, grow-bags, or large pots
5. Trellis and support method — strings to roof bar, canes, or hybrid
6. Watering and feed schedule — consistency more than volume

Get these six right and the rest is maintenance. Get any wrong and you'll fight it all summer.

Decision 1 — Cordon vs Bush

Cordon (indeterminate) tomatoes:

• Grow vertically, one main stem trained up a cane or string
• Side shoots removed weekly to focus energy on the main stem
• Continue producing fruit until first frost (October-November)
• Take more management time (15 min/week per plant)
• Better yield per m² in a greenhouse (typically 2-3 kg per plant over season)

Bush (determinate) tomatoes:

• Grow as a self-supporting compact bush, ~50-70 cm tall
• No side shoot removal needed
• Produce most of the crop in a 4-6 week window
• Less management (5 min/week per plant)
• Lower total yield per plant (typically 1-1.5 kg)

For UK greenhouse growing — cordon almost always wins. A 2.30 m ridge height (NORDIC standard) is wasted on bush types. Cordon tomatoes use the full vertical space; 6-8 plants in NORDIC M produces what 20+ bush plants would. The 15-minute weekly side-shoot routine is the gardener's commitment to that yield.

Exception: if you can't commit to weekly maintenance, choose bush. Bush types are also better for first-time greenhouse growers who haven't yet built the habit.

Decision 2 — Variety choice

For UK greenhouse growing in 2026, varieties with proven track record across our gardening community:

Cordon types — reliable producers:

• 'Shirley' — classic medium round, reliable, good disease resistance, prolific. The default UK greenhouse tomato.
• 'Sungold' — cherry, exceptionally sweet, F1 hybrid. Best-tasting cherry by wide margin.
• 'Gardener's Delight' — small-medium cherry, heritage open-pollinated, can save seed.
• 'Sweet Million' — abundant small cherries, almost foolproof, kids love them.
• 'Costoluto Fiorentino' — heritage Italian ribbed beefsteak, gorgeous, lower yield but exceptional flavour for cooking.
• 'Tigerella' — striped novelty, fun, reliable, good for showing off.

Bush types — for low-maintenance:

• 'Tumbler' — proper hanging basket / bush, abundant cherries.
• 'Red Alert' — early bush, ripens reliably in cool summers.

Avoid first time: beefsteak varieties like 'Marmande' or 'Brandywine' — they need more heat than UK greenhouses reliably provide; fruit set is unreliable in 18-22°C.

Disease resistance to look for: TMV (Tomato Mosaic Virus), V (Verticillium wilt), F (Fusarium wilt). Modern F1 hybrids almost always have these. Heritage varieties don't — that's the trade-off.

Decision 3 — Sowing dates for UK conditions

This is where most first-time growers get it wrong. UK gardeners follow Mediterranean seed-packet instructions and sow in mid-January. The plants then go leggy in February, get planted out into a cold greenhouse, sulk through April, and produce a poor crop.

Honest UK sowing schedule:

Why not earlier: UK light intensity in January-February is insufficient for seedling growth. Plants stretch (leggy) reaching for light. Healthier February seedlings outperform January legging-stretched ones by July.

For unheated greenhouses, push everything 2 weeks later — sow mid-March, plant out late May.

Decision 4 — Growing medium

Three viable approaches:

(a) Direct in greenhouse soil

• Best yields when soil is healthy
• Risk: soil-borne disease build-up after 2-3 seasons (clubroot, Fusarium, Verticillium)
• Solution: rotate annually OR remove + replace top 15cm soil every 2-3 years

(b) Grow-bags (commercial)

• Disease-free fresh medium each year
• 1 bag = 2-3 plants typical
• Limitation: dries out fast, needs daily watering by August
• Cost: £4-6 per bag × 6-8 plants = £25-50/season

(c) Large pots (35-45 cm diameter)

• Best of both — fresh disease-free medium, won't dry as fast as bags
• More expensive initially (~£15-30 per pot × 6-8 = £100-200) but reusable for 5+ years
• Cost-per-season ~£20-40 amortised

For NORDIC owners: pots on staging benches free up floor space for trailing crops or salad rotation. NORDIC's 2.30 m ridge accommodates cordon tomatoes in 35-cm pots on staging — 1.5 m of vertical growing space, plenty for 6-foot vines.

→ Deeper read: Greenhouse Staging and Shelving UK: What Works in NORDIC

Decision 5 — Trellis and support

For cordon types — three viable methods:

Method 1 — String to ridge bar (Mediterranean-style)

• Soft baler twine tied loosely around the main stem at first true leaves
• Other end tied to the greenhouse ridge bar or a horizontal rail under the ridge
• Plant twists around the string as it grows
• Pro: clean, professional, easy to manage
• Con: requires sturdy ridge bar attachment

Method 2 — Bamboo canes

• 2-2.5 m bamboo cane per plant, pushed firmly into soil/pot
• Tie main stem to cane every 15-20 cm with soft tie
• Pro: standalone, no greenhouse structure needed
• Con: canes lean by August under fruit weight; needs cross-bracing

Method 3 — Hybrid (cane base + string upper)

• Bamboo cane for first 1 m, then transition to string to ridge bar for upper growth
• Best stability + best vertical reach

For NORDIC greenhouses, string-to-ridge-bar method works beautifully — the 45×45 mm pine rafters hold the string load easily.

Decision 6 — Watering and feed

The two biggest tomato killers in UK greenhouses:

Inconsistent watering → blossom-end rot (BER). Fruit develops with a black/brown leathery patch at the bottom. Cause: calcium can't move into the fruit when water supply fluctuates. Once a plant gets BER, it usually keeps doing it.

The fix: consistent moisture. Water on a schedule, not "when you remember". Target: greenhouse soil/medium constantly damp 5 cm down (push finger in to check), never sodden, never bone-dry.

Practical watering schedule (UK greenhouse):

For 8 cordon plants, August demand is ~16-24 L/day. Plan for a water source within hose reach or rainwater collection at the greenhouse.

Feed schedule:

• Until first truss set fruit (mid-late May to mid-June): no feeding needed; growing-medium nutrients sufficient
• From first truss onward: tomato feed (high potassium) once a week, mixed at label rate (typically 10 mL per 5 L water)
• From August onward: twice weekly tomato feed
• Stop feeding 2 weeks before final harvest (typically early October)

Best feed types: any branded high-K liquid tomato feed (Tomorite is the household name; supermarket own-brand works equally well at half the price). Organic option: comfrey tea (homemade from a comfrey patch).

Common problems and fixes

Blossom-end rot (BER) — see watering section above. Calcium availability fix = consistent moisture. If already started, water more consistently and the next trusses will be fine.

Blight (Phytophthora infestans) — leaves get dark brown patches with pale halos; spreads fast in humid conditions. Greenhouse tomatoes are LESS prone than outdoor (controlled humidity helps), but still possible if SmartVent™ is closed during damp evenings. Prevention: keep vents open during the day, reduce overhead watering, space plants for airflow. Treatment: remove affected leaves immediately, burn (don't compost), spray with copper-based fungicide if early stages.

Yellow leaves (low nitrogen) — early-season yellowing of lower leaves = compost running out of nitrogen. Top-dress with general-purpose fertiliser OR start liquid feed earlier.

Yellow leaves (magnesium deficiency) — yellowing BETWEEN green veins on older leaves. Foliar spray with Epsom salts (1 tablespoon per 5 L water) gives instant fix.

Cracking — irregular watering after dry spell makes ripening fruit split. Same fix as BER: consistent moisture.

Greenfly / whitefly — yellow sticky traps work well as monitoring + light control. For heavy infestations, biological control (Encarsia formosa parasitic wasp for whitefly; ladybird larvae for aphids) outperforms pesticides in a greenhouse setting and is standard horticultural best practice.

Catfacing / weird-shaped fruit — cold temperatures at flowering (<13°C night) disrupt pollination. Unheated UK greenhouses get this on May-planted crops. Twin-wall polycarbonate (NORDIC's 4mm CrystalLight™, U≈3.9 W/m²K) buffers overnight temperature drops ~33% better than single horticultural glass — helps prevent the marginal cold snaps that cause catfacing. Solution: plant out only when night temps reliably 10°C+, OR add overnight heat for May.

Yield expectations — what's realistic

For a UK greenhouse with cordon tomatoes, on-schedule maintenance, no major pest/disease setbacks:

These are realistic numbers — not seed packet "up to 50 kg per plant" marketing. Real growers in real UK greenhouses get 2-3.5 kg per cordon plant over the season.

If you're consistently under 1.5 kg per cordon plant, something's wrong: insufficient feed, inconsistent watering, late sowing, or wrong variety for the conditions.

Quick reference — month-by-month tomato calendar

• February (late): sow seed in heated propagator, 18-22°C
• March: prick out, pot on, full light propagator
• April: pot on to 13-15 cm, move to greenhouse daytime
• Early May: plant out into final position (greenhouse min night 10°C)
• Mid May: install support system, start side-shoot removal (weekly for cordon)
• June: first flowers, start feeding when first truss sets fruit
• July: first ripe fruit (cordon); switch to daily watering; ramp up feed
• August: peak harvest; daily watering; twice-weekly feed; remove lower leaves below ripening trusses for airflow
• September: continue harvest; reduce watering as nights cool
• Early October: stop feeding; pinch out main stem growing tip; let final trusses ripen
• Mid-late October: harvest all remaining fruit (green ones ripen indoors in paper bag with banana); compost plants

→ Deeper read (when published): Greenhouse Monthly Calendar UK — what to do each month

Frequently asked questions

When should I sow tomato seeds for a UK greenhouse?

Late February to mid-March is the honest sweet spot. Earlier (January-early February) and seedlings stretch from low UK light; later (April) and the season is compressed. Use a heated propagator at 18-22°C for germination.

Cordon or bush tomatoes for a UK greenhouse?

Cordon (indeterminate) almost always wins in a UK greenhouse. They use the full vertical space (NORDIC's 2.30 m ridge), produce 2-3× the yield per plant of bush types, and crop continuously until first frost. The trade-off is 15 minutes per week of side-shoot removal.

What's the best tomato variety for a UK greenhouse?

'Shirley' for reliable medium round (the UK greenhouse default), 'Sungold' for sweetest cherry, 'Sweet Million' for high-yield small cherries that even kids will pick. Avoid beefsteaks like 'Marmande' for first attempts — they need more reliable heat than UK greenhouses provide.

How many tomato plants in a NORDIC greenhouse?

NORDIC S: 4-6 cordon. NORDIC M: 6-10. NORDIC L: 8-12. NORDIC XL: 12-16. NORDIC XXL: 16-20. Plant spacing 50 cm apart for cordon, allowing room for staging on one wall and a working aisle.

How much water do greenhouse tomatoes need?

In peak August: 2-3 L per cordon plant per day, often twice on 30°C+ days. For 8 plants that's 16-24 L/day. Plan rainwater collection at the greenhouse OR hose reach. Consistent moisture is more important than absolute volume — fluctuations cause blossom-end rot.

Do I need to feed greenhouse tomatoes?

Yes, once the first truss has set fruit (typically mid-late June). High-potassium tomato feed (Tomorite or supermarket equivalent) once a week through July, twice a week in August. Stop feeding 2 weeks before final harvest in October.

What's the highest-yield setup for greenhouse tomatoes?

Cordon variety like 'Shirley', planted out in early May into large pots (35-45 cm) on staging benches in a 2.30 m ridge greenhouse, supported by string-to-ridge-bar, with consistent watering (daily July-August) and weekly feeding. A NORDIC XXL run this way yields 40-70 kg per season across 16-20 plants.

Why do my tomatoes get blossom-end rot?

Inconsistent watering. Calcium can't move into developing fruit when soil moisture fluctuates between wet and dry. Once the patch appears on a fruit, that one's compromised — but the next trusses will be fine if you fix the watering schedule. Consistent daily moisture beats heavy occasional drenching.

Can I leave tomatoes unattended for a week in summer?

Not really. By August, greenhouse tomatoes need daily watering (2-3 L per plant) AND ventilation. A week unattended in heat = stressed plants + lost fruit. Options for holidays: (1) automatic drip watering system (~£40 + setup), (2) family/neighbour daily visit, (3) plan holidays for May or October.

Final CTA

A wooden greenhouse with 2.30 m ridge height + screw-fixed twin-wall polycarbonate gives you the controlled environment for serious tomato growing — full vertical reach for cordon varieties, even light from twin-wall diffusion, and SmartVent™ auto-vents that handle hot UK summer days without your involvement.

→ Browse the NORDIC range — five sizes from £1,499 → Not sure which size? See What Size Greenhouse Do I Need? → Already have a greenhouse? See Wooden Greenhouse Maintenance UK for the annual schedule

Related Reading

• Monthly greenhouse calendar UK — what to sow, plant, and harvest each month
• Greenhouse heating for UK winter — keeping tomatoes through October
• Greenhouse staging and shelving — making the most of vertical space
• Where to place a greenhouse in your UK garden — sun, shelter, access
• How to insulate a greenhouse for UK winter
• Waldenhaus wooden greenhouses — main hub
• Shop the NORDIC range — from £1,499