Humidity in the Greenhouse

How important is controlling humidity in your greenhouse?

Some would say it is vitally important to control the humidity in your greenhouse. Expensive instruments can be purchased to measure exact humidity and automatically adjust it. However, for the average greenhouse owner who isn't monitoring optimal conditions for growing thousands of plants to sell, controlling humidity is sometimes all about controlling ventilation. Plants need air. Air circulation improves transpiration in plants. Thus, good air circulation often takes care of humidity problems as well as temperature problems. One of the best things I ever purchased for my greenhouse was an automatic window opener. Window openers (more often called vent openers) open when the temperature inside the greenhouse gets hot (85 degrees or more) and close when that temperature cools down. An additional benefit is that this also helps to increase air flow (drier, cooler air from the outside is exchanged with the hot, humid air). Plants seem exceptionally happy about good air flow.

Humidity in the greenhouse higher than 80% can sometimes cause molds to grow --BAD for plants as they sometimes are disease. However, some humidity is beneficial as plants also dry out faster in a greenhouse.

For a little more advanced analysis of humidity and greenhouses, visit Ohio State University Publication