RHS Guide to Growing Tomatoes: Expert Tips for a Bountiful Harvest

Introduction

Tomatoes are the crown jewel of the summer garden: versatile in the kitchen, rewarding to grow, and surprisingly simple with the right know-how. The Royal Horticultural Society (RHS) has distilled decades of research and trial-ground experience into best practices that help both novice and seasoned gardeners succeed. In this comprehensive, SEO-friendly guide, you’ll learn everything the RHS recommends for growing tomatoes—from choosing the right varieties and preparing the soil to sowing seeds, managing pests and diseases, and harvesting juicy, flavour-packed fruit. Follow these proven techniques, and you’ll be picking tomatoes long into autumn.

1. Selecting the Right Tomato Varieties

The RHS trials hundreds of cultivars each year. Key distinctions:

• Determinate (Bush) Tomatoes
  • Grow to a fixed height (60–90 cm), set fruit over a short period.
  • Ideal for containers or small gardens.
  • RHS favourites: ‘Balcony Red’, ‘Red Alert’.
• Indeterminate (Cordon) Tomatoes
  • Vining habit; fruit continuously until frost.
  • Require staking or cage support.
  • RHS award-winners: ‘Gardener’s Delight’, ‘Ailsa Craig’, ‘Moneymaker’.
• Cherry & Cocktail Tomatoes
  • Small, prolific fruit.
  • Great for salads and snacking.
  • RHS top picks: ‘Sweet Aperitif’, ‘Sungold’.
• Beefsteak & Heritage Types
  • Large, meaty fruits for slicing.
  • Often heirloom varieties prized for flavour.
  • RHS classics: ‘Brandywine’, ‘Black Russian’.

2. Site Selection and Soil Preparation

Tomatoes need sun, shelter, and fertile, free-draining soil:

1. Aspect:
   • South or west-facing for at least 6 hours of direct sun per day.
   • Sheltered from strong winds to protect fruit-setting flowers.
2. Soil:
   • pH: 6.0–6.8 (slightly acidic).
   • Structure: Light, friable loam but enriched with organic matter.
   • Improvement:
     • Dig in well-rotted garden compost or potting compost (5–10 cm deep) the autumn before or at planting.
     • Apply a balanced, slow-release fertilizer (RHS recommends 5–10 10 NPK) at transplanting.
3. Rotation:
   • Avoid planting tomatoes (and other nightshades) where potatoes, peppers, or aubergines grew in the past two years to reduce soil-borne diseases.

3. Sowing and Pricking Out

3.1 Sowing Seeds Indoors

• Timing: Sow early March–April, 6–8 weeks before the last expected frost (UK: late May).
• Compost: Use a sterile, seed-sowing mix.
• Depth: 5 mm, spaced 3–4 cm apart in modules or 7 cm pots.
• Conditions:
  • Cover seeds lightly, water gently, cover tray with clear lid.
  • Maintain 18–21 °C; germination in 5–10 days.

3.2 Pricking Out & Hardening Off

• First Prick: When seedlings have two sets of true leaves, move into 7–10 cm pots, burying stems up to the first leaves to encourage strong root development.
• Harden Off: From mid-May, over 7–10 days, acclimatize plants by exposing them to increasing outdoor conditions—start in shade, progress to full sun.

4. Planting Out and Training

4.1 Planting Out

• Timing: After all risk of frost (UK: late May–early June).
• Spacing:
  • Cordons: 45–60 cm apart in rows 60–90 cm apart.
  • Bush: 30–45 cm apart.
• Planting Depth: Bury up to the lowest true leaves. Firm in gently and water well.

4.2 Support & Training

• Staking (Cordon Tomatoes):
  • Insert sturdy cane at planting.
  • Tie stem loosely with garden twine every 15–20 cm as it grows.
• Caging (Bush Varieties): Use tomato cages or mesh supports for continuous varieties.

5. Watering, Feeding, and Mulching

5.1 Watering

• Keep soil consistently moist, especially when fruit is swelling.
• Water at the base of plants early in the day to reduce foliage wetness and disease risk.

5.2 Feeding

• Liquid Feed: Weekly feed with tomato-specific liquid fertilizer (high potassium formula, e.g., 5–15 30 NPK) once the first fruits set.
• Top Dressing: Reapply balanced granular feed mid-season if growth appears weak.

5.3 Mulching

• Apply a 5 cm layer of organic mulch (e.g., well-rotted manure, compost, straw) to conserve moisture, suppress weeds, and maintain even soil temperature.

6. Pruning and Pinching Out

• Cordon Tomatoes: Remove side shoots (suckers) up to the first flower truss to focus energy on the main stem.
• Bush Varieties: Minimal pruning—remove only diseased or overcrowding foliage to improve air flow.

7. Pest and Disease Management

RHS Integrated Pest Management (IPM) approach emphasizes prevention and monitoring:

Regularly inspect plants, remove debris, and rotate crops to keep problems at bay.

8. Pollination and Fruit Set

• Tomatoes are self-pollinating, but gentle shaking of stems or tapping under lower trusses encourages pollen release and fruit set—especially useful in glasshouses.

9. Harvesting and Storing

• Harvest When: Fruit is fully coloured (red, yellow, orange, or purple depending on variety) and slightly soft to the touch.
• Frequency: Every 2–3 days to encourage new fruiting.
• Storage:
  • Short-Term: Room temperature away from direct sun for up to a week.
  • Long-Term: Refrigerate only overripe fruit; best eaten soon after picking for maximum flavor.

Conclusion

By following the RHS’s expert recommendations—selecting award-winning varieties, preparing sunny, fertile sites, sowing and hardening off carefully, supporting and pruning appropriately, and vigilantly managing pests—you can cultivate a bumper crop of home-grown tomatoes bursting with flavour. Whether you grow in containers on a balcony or in rows in a vegetable patch, these proven techniques will set you up for success and help you savour the satisfaction of picking tomatoes straight off the vine.

Top 10 Questions & Answers

1. When should I sow tomato seeds according to RHS?
   Sow 6–8 weeks before the last frost, typically early March–April in the UK.
2. Which RHS tomato varieties are best for containers?
   Try determinate types like ‘Balcony Red’ or bush cultivars such as ‘Red Alert’.
3. How far apart should I plant cordon tomatoes?
   Space them 45–60 cm apart, with rows 60–90 cm between.
4. Do I need to pinch out suckers on bush tomatoes?
   Generally no—only on indeterminate (cordon) types; leave suckers on determinate plants.
5. What fertilizer does the RHS recommend for tomatoes?
   A high-potassium feed (e.g., NPK 5–15 30) weekly once fruit sets; balanced feed at planting.
6. How do I prevent blossom end rot?
   Maintain consistent moisture, ensure calcium availability, and avoid sudden dry–wet swings.
7. Can I grow tomatoes in pots on my balcony?
   Yes—use 20 L pots, fertile compost, regular feeding, and support stakes for cordons.
8. What’s the best way to water tomato plants?
   Water at the base early in the day, keeping foliage dry to reduce disease.
9. How often should I harvest?
   Every 2–3 days—frequent picking encourages more fruit to form.
10. How do I protect tomatoes from late blight?
    Ensure good air flow, remove infected leaves immediately, and avoid overhead watering; destroy diseased plants to prevent spread.