Don’t bake your greenhouse plants in the summer sun

The maker of one of Britain’s most iconic greenhouses has given some timely advice about keeping plants cool in the summer sun.

Paul Smith, the Technical Director of Griffin Glasshouses, producers of bespoke and the National Garden Scheme range, warns that even in overcast weather the temperature inside can reach levels that are harmful to plants.

“Small structures are most at risk because the volume of air compared to the glass area is small causing it to heat up very quickly. The best rule is that a greenhouse should have 25% of the floor areas as ventilation. Our structures are deliberately high because this has the effect of a chimney drawing the hot air up and out through the vents,” he explained.

Paul’s top tips are:

• Water last thing at night and early in the morning as this reduces the evaporation of moisture and also prevents water droplets forming on foliage and risking scorching.
• If you are considering greenhouse shading reflective material is best as this drives the heat away from the greenhouse. Darker colours absorb heat, sending it back into the building Whatever you use, make certain the shading does not block the ventilation.
• If you do not have shading there are proprietary materials that can be painted or sprayed on to the inside of the glass. This is easily removed in the autumn.
• Don’t forget that the doors can be a major source of ventilation and, if possible, they should remain open at night.
• Vines are an excellent and natural form of shading.

“Remember, if you are working in your greenhouse in the sun and it’s too hot for you, it is most probably the same for your plants,” warns Paul.