Chapter 10

Temperature Requirements for Greenhouse Crops

Temperature Drop (DIP)

Researchers have discovered that most of the stretch occurs in the first 3 hours beginning exactly at daybreak when plants first become photosynthetically active. By lowering the temperature below the night temperature at daybreak for a couple of hours, much of the plant stretch can be eliminated. Normal temperature settings can then be restored for the rest of the day. Stretching has been significantly reduced with much less impact on the average daily temperature. A typical temperature dip is 5 degrees below the night temperature. This practice is referred to as temperature drop, or DIP by 5 to 15 degrees F (2.8–8.3°C) before sunrise for a 2- to 3-hour period. Exhaust fans should be activated so that the greenhouse air temperature is lowered sufficiently by sunrise. Generally, the greater the magnitude of the temperature drop, the stronger its effect on plant height.

Click on the following topics for more information on temperature requirements for greenhouse crops.