Managing greenhouse temperatures in summer

The job of a greenhouse is to hold heat from the sun – but too much dry heat can cause stress and tissue damage to even the most sun-loving crops. Here are a few simple steps you can take to keep your greenhouse cool, protecting your crops throughout the summer.

You may begin to see wilting, leaf scorch or desiccated young foliage in temperatures above 27°C. Sustained high temperatures can also cause poor pollination and damage to developing fruits.

There are four essential things to do during this time to help your greenhouse crops thrive:

Water regularly
Provide adequate ventilation by opening all doors and any vents early in the morning
Create shade from direct sunlight using netting, blinds or shade paint
Damp down

What is damping down?

During hot periods, increased humidity slows down the rate that plants transpire: releasing water from their leaves into the air around them. If the air is humid and already saturated with water, the water inside the leaves stays put.

The more water your plants can retain, the less likely they are to suffer from heat stress. Damping down is an effective way to decrease water loss and keep your plants happy and healthy – simply by pouring water onto the floor of the greenhouse.

Damp down first thing in the morning. As the water evaporates, it will create enough humidity throughout the day to prevent your plants from suffering heat stress. It also helps to reduce problems with red spider mites, which enjoy a dry environment.

Repeat the process in the afternoon if necessary.