Greenhouse Herb Gardening: Cooling
As much as you want your greenhouse to provide your plants with warmth throughout the season, too much heat can destroy your plants. A smart thing to do is to set up a thermometer inside your greenhouse, one that will give you maximum and minimum values. This way you can monitor the heat of your greenhouse and see whether or not it is becoming too hot for your herbs. Just remember that some herbs like it very warm, while others do not. Do some research on what are good temperatures for the herbs you intend to grow and strike a good balance.
During the summer months, greenhouses can become extremely hot. When they are getting too hot, the plants you have in your greenhouse can begin to suffer and show signs that they are struggling. If your plants are wilting or not flowering when they should be, then they can be stressed. Another sign of stressed plant is that pests are all around it.
Many gardeners choose not to use their greenhouses beginning the spring and throughout the summer. They give their plants a chance to enjoy some natural air, sunlight, and rain, as well as natural temperatures. This is actually the easiest way to avoid killing your plants during the warm months, simply remove them from the greenhouse.
Some fragile plants or plants that are particularly susceptible to certain pests are kept in greenhouses, though. In which case, a gardener will have to find a way to cool the structure. One way is to use a shade cloth to block out some of the sun and prevent the temperature from rising too high inside the greenhouse.
Another method is to use an evaporative cooler. This does the opposite of a heater. It forces heat to leave the greenhouse, and helps keep the plants cool. Just like the heater, there are several different styles, sizes, energy requirements, and possible restrictions you will have to follow when using such a unit. If you are willing to have your plants outside of your greenhouse during the spring and summer, go for that! It's your cheapest and easiest way of keeping your plants cool.