In The Greenhouse This July

July is a high-maintenance but high-reward month in the greenhouse. With warmth, long days, and peak growth, here’s how to keep your greenhouse productive and healthy: 

🌡️ Ventilation and Temperature Control 

• Ventilate daily: Open roof vents, side vents, and doors to avoid overheating. 

• Use shading: Apply shade paint or hang shading cloths to reduce scorching sunlight. 

• Damp down the floor: Watering paths or staging helps cool the air and increase humidity—especially important for crops like cucumbers. 

💧 Watering and Feeding 

• Water daily in hot weather, especially for tomatoes, cucumbers, peppers, and aubergines. 

• Avoid overwatering: Let the top of the compost dry slightly between waterings to avoid root rot. 

• Feed weekly: Use a high-potash tomato feed once fruits start forming. 

🍅 Pruning and Training 

• Pinch out side shoots on cordon tomatoes regularly. 

• Support climbing crops like cucumbers and tomatoes with string, canes, or trellis. 

• Remove lower leaves on tomatoes as they yellow—this improves airflow and reduces disease. 

🐛 Pest and Disease Watch 

• Watch for pests: Aphids, whitefly, red spider mites, and mealybugs can thrive in greenhouses. 

• Use sticky traps and natural predators (like ladybirds) or organic sprays if needed. 

• Check for mould or mildew: Especially if humidity is high and airflow is poor—remove affected leaves promptly. 

🌱 Sowing and Growing 

Sow now: 

• Autumn/winter salads like lamb’s lettuce, mizuna, and rocket 

• Spring cabbages, leeks (late), and chard for autumn planting 

• Take cuttings of herbs (like basil and mint) or bedding plants (like pelargoniums) 

🧹 General Maintenance 

• Keep it clean and tidy: Remove dead leaves, weeds, and any decaying matter. 

• Inspect automatic systems (vents, irrigation) to ensure they’re working. 

• Top up pots: Refresh compost around long-term crops if it’s compacted or drying quickly.