Ideal Greenhouse Temperature Ranges for Mixed Crops

For a 10×20 ft greenhouse with diverse crops:

• Maximum: 90°F (32°C). Above this, cool-season crops (lettuce, spinach) bolt and tomatoes/peppers stop setting fruit.
• Minimum: 40°F (4°C) for cool-season crops; 55°F (13°C) for heat-loving crops.

Management Strategies

• Install heat-activated roof vents or exhaust fans.
• Use shade cloth in summer.
• Start cool crops in winter; heat-loving crops in late winter/early spring.
• Germinate seeds at 75°F, then lower to 60–65°F for stocky growth.

Spinach bolts above 65°F; avoid growing it in a warm greenhouse.