Growing Melons in a Greenhouse: A Step-by-Step UK Guide to Sweet Success

Introduction

Imagine picking a perfectly ripe, sweet, and fragrant melon right from your own greenhouse—no air miles, just pure flavour. While melons are typically associated with warmer climates, growing melons in a greenhouse in the UK is entirely possible with the right approach. A protected environment provides the warmth, humidity, and controlled conditions melons crave to thrive.

This step-by-step guide will walk you through everything you need to know about growing melons in a greenhouse—from choosing varieties to sowing, pollination, pruning, feeding, and harvesting your very own homegrown crop.

Why Grow Melons in a Greenhouse?

• 🌡️ Controlled warmth – Essential for germination and fruit development
• 🍈 Better yields – Protects against cold snaps and poor weather
• 🐝 Supports pollination and fruit set – Easier to control or assist manually
• 🏡 Grows in UK conditions – Makes tropical fruits a homegrown reality
• 🍯 Superior flavour – Sweeter and juicier than shop-bought melons when fully ripened on the vine

Best Melon Varieties for UK Greenhouses

Tip: Choose early maturing, compact varieties with good disease resistance for best results in UK greenhouses.

When to Grow Melons in the UK

Melons need 12–20 weeks from sowing to harvest depending on variety and growing conditions.

Where to Grow Melons in a Greenhouse

Melons need:

• Consistent warmth (18–30°C ideally)
• High humidity during early growth
• Good ventilation to prevent fungal issues
• Rich, well-drained soil or compost
• Space to trail or be trained vertically

Grow in:

• Ground beds inside the greenhouse
• Large grow bags or containers (minimum 30cm deep)
• Raised planters or greenhouse borders

Step-by-Step: Growing Melons in a Greenhouse

Step 1: Sow Melon Seeds Indoors

1. Sow seeds 1–2cm deep in 9cm pots using seed compost
2. Keep at 21–25°C (heated propagator or sunny windowsill)
3. Germination takes 5–10 days
4. Once seedlings have 2–3 true leaves, pot them on into larger pots
5. Harden off before moving into the greenhouse

Tip: Melons dislike root disturbance—handle carefully when potting on.

Step 2: Prepare the Greenhouse Bed or Container

• Dig in well-rotted manure or compost
• Add a general-purpose fertiliser before planting
• Space plants 45–60cm apart, or one per grow bag or large pot
• Insert stakes or strings if training vertically

Soil temp should be above 15°C before planting. Warm beds with black plastic sheeting if needed.

Step 3: Transplant into Greenhouse

1. Plant seedlings deep, up to the first set of leaves
2. Water well and mulch to retain moisture
3. Tie young plants loosely to supports if growing upright
4. Keep greenhouse temperature 18–25°C daytime, not below 15°C at night

Training and Supporting Melons

You can train melons vertically or let them sprawl across the greenhouse floor.

Vertical Training (Recommended for Small Spaces):

• Tie main stem to string or cane
• Remove side shoots up to 60cm, then allow 2–3 shoots to develop and bear fruit
• Support developing fruit with net bags or slings

Horizontal Training (For Larger Greenhouses):

• Allow vines to trail across the bed
• Thin out overcrowded growth
• Turn vines occasionally to avoid fruit sitting on damp soil

Pollination: How to Ensure Fruit Set

Most melons need manual pollination in greenhouses due to fewer natural pollinators.

Steps for Hand Pollination:

1. Identify male flowers (thin stem) and female flowers (mini fruit at the base)
2. Gently transfer pollen using a soft brush or by rubbing flowers together
3. Pollinate in the morning when flowers are open
4. Repeat for a few days to ensure good fruit set

Tip: Some newer F1 varieties are self-pollinating—check the label.

Feeding and Watering

Watering:

• Keep compost moist but not wet
• Water in the morning to reduce fungal issues
• Reduce watering once fruit starts swelling to concentrate sugars

Feeding:

• Start feeding when plants begin to flower
• Use a high-potash feed (like tomato feed) every 7–10 days
• Stop feeding once fruit matures

Melon Care: Pruning and Thinning

Pruning:

• Pinch out the growing tip after 5–6 leaves to encourage side shoots
• Limit each plant to 3–4 fruits for better size and flavour
• Remove excess side shoots and leaves that shade fruit

Thinning Fruit:

• Once fruit sets, remove extras to allow remaining melons to develop fully
• Leave one fruit per shoot for best results

Harvesting Greenhouse Melons

When to Harvest:

• When fruits smell fragrant and the base (stem end) gives slightly to pressure
• Some types (e.g., cantaloupe) may detach naturally when ripe
• Look for netting/cracking on the skin and colour change

How to Harvest:

• Use scissors or a knife to cut from the vine
• Harvest in the morning when cool for best storage

Tip: Don’t wait too long—melons over-ripen quickly once mature.

Storing and Using Homegrown Melons

Storage:

• Store ripe melons in the fridge for up to 1 week
• Keep uncut in a cool spot if not ready to eat
• Don’t wash until ready to use

How to Use:

• Slice and eat fresh
• Add to salads with mint and feta
• Blend into smoothies or juices
• Make melon sorbet or granita
• Use in savoury dishes with cured meats

Common Greenhouse Melon Problems and Solutions

Growing Melons in Small Greenhouses or Conservatories

• Choose compact varieties like Minnesota Midget
• Train up canes or strings to save space
• Hand-pollinate and ensure daily ventilation
• Provide support for each fruit using net bags or slings

Conclusion

Growing melons in a UK greenhouse is not just a fun gardening challenge—it’s a delicious reward. With the right care, warmth, and a bit of hands-on attention, you can enjoy juicy, sun-ripened melons straight from your own garden. Whether you’re growing cantaloupes, galias, or mini melons, this tropical treat can flourish even in British weather when protected and nurtured under glass.

Follow this step-by-step guide to ensure a sweet, successful melon harvest and turn your greenhouse into a fruity paradise.

Top 10 Questions and Answers About Growing Melons in a Greenhouse

1. Can I grow melons in a UK greenhouse?

Yes! With the right variety and conditions, melons grow very well under glass in the UK.

2. When should I plant melon seeds?

Sow indoors in March or April, and transplant to your greenhouse by late April or May.

3. Do I need to hand-pollinate melons?

Yes—especially in greenhouses. Use a soft brush to transfer pollen between flowers.

4. What’s the best melon variety for beginners?

Emir F1 is easy, reliable, and suited to UK greenhouses.

5. How much space does a melon plant need?

Each plant needs 45–60cm of space, plus support if trained vertically.

6. Can I grow melons in containers?

Absolutely—use 30–40cm deep containers, rich compost, and regular feeding.

7. How many melons can one plant produce?

Limit to 3–4 fruits per plant for best size and sweetness.

8. How do I know when melons are ripe?

Check for sweet aroma, a slight softness at the base, and changes in skin texture.

9. How long do melons take to grow?

From seed to harvest takes about 12–20 weeks, depending on variety.

10. Can I grow melons alongside tomatoes or cucumbers?

Yes—but ensure good airflow and space to avoid disease competition.