What are typical day and night temperature ranges for many greenhouse crops?

• A. Day around 70–75°F (21–24°C) and night around 60–65°F (15–18°C).
• B. Day around 80–85°F (27–29°C) and night around 50–55°F (10–13°C).
• C. Day around 60–65°F (15–18°C) and night around 70–75°F (21–24°C).
• D. Day around 75–82°F (24–28°C) and night around 55–60°F (13–16°C).

Answer: (A)

A typical greenhouse management target is to keep the day temperature around 70–75°F (21–24°C) and the night temperature around 60–65°F (15–18°C). This combination supports strong photosynthesis during the day while providing a comfortable, lower-temperature period at night that reduces excessive respiration and helps plants recover and store energy. It also helps avoid heat stress that can occur with hotter days and avoids the slower growth that can come with too-cold nights. For many crops, this day–night differential promotes steady growth, good flowering, and efficient energy use. Other options push temperatures into ranges that can stress crops—either too hot by day with very cool nights, or an inverted pattern where nights are warmer than days—leading to less optimal growth.