Greenhouses

Greenhouses are invaluable to the keen gardener, enabling reliable production of warmth-loving crops such as exotic flowers, salad leaves and fruit and vegetables. But even these sun seekers have a limit. When summer temperatures rise, it's important to ensure that greenhouse conditions are perfect.

• Sun scorch can be damaging. Some form of shading is essential for many plants. 
• Keep temperature down by continued ventilation. The major problem is keeping the temperature low enough during a hot spell. Ventilation now becomes vitally important and will be necessary at night as well as during the day. Opening all the ventilators and propping the door open may be required 24 hours a day.
• Damp down floors if weather sunny to cool and humidify greenhouse.
• Routine feeding is necessary as most plants are now growing vigorously. A liquid feed at fortnightly intervals is suitable as a basic treatment, but fruit-bearing plants such as cucumbers and tomatoes need feeding every 7-10 days.
• Keep watch for pests and diseases. Red spider mite, greenfly, whitefly, thrips, grey mould and mildews are the major headaches – spray promptly if you see them, but read the rules for safe spraying before you begin. If you chose, hang up yellow greenhouse fly catchers or investigate biological controls as an alternative. 
• Take cuttings - roots usually form quickly in the warm conditions.