What to Grow in a Greenhouse in June

As the days stretch longer and temperatures rise, June marks a particularly exciting month for greenhouse gardeners across the UK. The lingering chill of spring has given way to the balmy promise of summer, and your greenhouse becomes a buzzing hub of activity. Whether you’re nurturing tender young plants, coaxing fruits into ripeness, or experimenting with exotic crops, June is a month bursting with growing potential.

But what exactly should you be planting, sowing, and tending to in your greenhouse in June? Let’s dive into the best crops to grow, essential tasks to keep your greenhouse thriving, and some handy tips to make the most of this peak growing season.

Why June is Special for Greenhouse Growing

Greenhouses offer a sheltered environment, extending the growing season and allowing you to cultivate plants that would struggle outdoors. By June, the threat of frost has passed in most of the UK, but a greenhouse still offers the advantage of controlled temperatures, protection from heavy rain, and a haven from pests.

June is a transitional month. Early crops sown in spring are reaching maturity, while summer sowings are just getting started. It’s a time of both harvest and renewal.

Top Crops to Grow in Your Greenhouse in June

1. Tomatoes

Tomatoes are greenhouse royalty in the UK. By June, your tomato plants should be well established, but it’s not too late to plant more if you have the space. Choose varieties suited to greenhouse growing, such as ‘Moneymaker’, ‘Sungold’, or ‘Alicante’.

Tips:

• Ensure plants are supported with canes or string.
• Regularly pinch out side shoots on cordon varieties.
• Feed weekly with a high-potash fertiliser once fruits start to form.
• Keep an eye on ventilation; tomatoes dislike stuffy conditions.

2. Peppers and Chillies

Both sweet peppers and fiery chillies thrive in the warmer, more stable conditions of a greenhouse. By June, young plants should be settling into their final pots or beds.

Tips:

• Maintain consistent watering to prevent bitter fruits.
• Pinch out the growing tips to encourage bushier plants.
• Look out for aphids and whitefly—use biological controls if necessary.

3. Cucumbers

Cucumbers are another greenhouse favourite. Opt for ‘all-female’ varieties like ‘Carmen’ or ‘Mini Munch’ to avoid the hassle of pollination.

Tips:

• Provide support with vertical strings or mesh.
• Mist the air to increase humidity.
• Feed fortnightly with liquid fertiliser.
• Watch out for powdery mildew; good airflow is key.

4. Aubergines

Though a little more demanding, aubergines can be very rewarding to grow under glass. Varieties like ‘Black Beauty’ or ‘Slim Jim’ perform well in greenhouses.

Tips:

• Stake plants to support heavy fruits.
• Hand-pollinate flowers to improve fruit set.
• Keep soil consistently moist but not waterlogged.

5. Melons

For the adventurous gardener, melons are a real treat. With their need for warmth, they’re perfectly suited to greenhouse life. ‘Sweetheart’ and ‘Ogen’ are good options for UK growers.

Tips:

• Train vines onto supports to save space.
• Hand-pollinate flowers for better yields.
• Maintain high humidity but ensure adequate ventilation.

6. Salad Crops

Quick-growing salad leaves like lettuce, rocket, mizuna, and spinach can be succession sown through June for a continuous harvest.

Tips:

• Grow in trays or shallow containers.
• Provide shading to prevent bolting.
• Water regularly to keep leaves tender.

7. Basil and Other Herbs

Tender herbs such as basil, coriander, and parsley love the warm, sheltered environment of a greenhouse. June is the perfect time to sow or plant them out.

Tips:

• Grow basil near tomatoes; they thrive in similar conditions.
• Pinch out flower buds to encourage leaf production.
• Use fresh compost for sowing to prevent damping off.

8. Strawberries

While strawberries grow well outdoors, growing them in a greenhouse gives you an earlier and often more abundant crop.

Tips:

• Grow in hanging baskets or growbags to maximise space.
• Pollinate flowers by gently brushing with a soft paintbrush.
• Mulch around plants to retain moisture and keep fruits clean.

9. Courgettes and Squash (Under Cover)

Although these plants can be grown outside, early crops benefit from the warmth of a greenhouse. Compact varieties like ‘Patio Star’ are well suited.

Tips:

• Provide plenty of space—these can be sprawling plants.
• Hand-pollinate for reliable fruit set.
• Water heavily and mulch to retain soil moisture.

Greenhouse Maintenance Tasks in June

Alongside planting, June is a busy month for greenhouse maintenance. Here are key tasks to stay on top of:

1. Ventilation and Shading

• Open vents and doors during the day to prevent overheating.
• Install shading cloth or use shade paint to protect plants from scorching.
• Use automatic vent openers if possible—they’re a game-changer.

2. Watering

• Watering needs increase dramatically in June’s warmth.
• Water early in the morning or late in the evening to minimise evaporation.
• Consider installing drip irrigation or capillary matting for consistency.

3. Humidity Control

• Increase humidity by damping down floors and staging.
• This helps prevent red spider mite infestations, which thrive in dry conditions.

4. Pest and Disease Monitoring

• Check daily for common greenhouse pests: aphids, whitefly, red spider mites.
• Introduce biological controls like parasitic wasps or predatory mites.
• Remove yellowing leaves and debris to prevent fungal diseases.

5. Feeding

• Regular feeding is essential for heavy-cropping plants.
• Use a balanced liquid fertiliser for leafy crops and a high-potash feed for fruiting plants.
• Don’t overfeed young plants—gradual is best.

Succession Sowing: Keep It Going

One of the joys of greenhouse gardening is the ability to sow crops in succession for continuous harvests. In June, keep sowing:

• Lettuce, rocket, spinach – every 2-3 weeks.
• Radishes – a quick crop for instant gratification.
• Spring onions – sow in modules for easy planting out.
• Dwarf French beans – enjoy tender pods into late summer.

Experimenting with Exotics

Feeling adventurous? June is the time to try more unusual greenhouse crops. Consider:

• Okra (Ladies’ Fingers): Needs consistent warmth but thrives under glass.
• Cape Gooseberries (Physalis): These sweet, tangy fruits are surprisingly easy to grow.
• Sweet Potatoes: Slips can be grown in containers or raised beds inside a greenhouse.

These crops can add diversity and a touch of the exotic to your gardening repertoire.

A Word on Greenhouse Automation

If you find yourself spending hours adjusting vents, watering, and shading, it might be time to consider some automation:

• Automatic vent openers adjust as temperatures rise and fall.
• Self-watering systems reduce manual watering needs.
• Temperature and humidity monitors with alerts help you maintain optimal conditions.

A little investment can save you time and improve plant health.

Conclusion: Making the Most of June

June is a pivotal month for greenhouse gardening in the UK. It’s a time of abundance, growth, and careful management. With a little planning and daily attention, your greenhouse can become a powerhouse of productivity.

From juicy tomatoes to lush salads, spicy chillies to sweet strawberries, the variety of crops you can grow in June is immense. By staying on top of watering, ventilation, and pest control, you’ll ensure your plants thrive through the hottest months ahead.

So, roll up your sleeves, grab your watering can, and make the most of your greenhouse this June. The rewards will be delicious.