Optimum greenhouse temperature varies for different plants. Tropical varieties and plants grown for their fruit, such as oranges and tomatoes grow best in temperatures that are at least 60 degrees Fahrenheit and up to 85 degrees. Anything hotter than 90 degrees will eventually kill most plants. Greenhouses in hot environments often need cooling units during the summer.
Greenhouse temperatures for house plants and vegetables where leaf and root are desired prefer slightly cooler temperatures. Wintering vegetables and shrubs also prefer temperatures from 45 degrees up to 75 degrees on the high end, but best growth is achieved at roughly 60 degrees. Hot and cold months could necessitate the use of heating elements or coolers and good ventilation.
Greenhouse temperatures can vary inside each greenhouse, creating many micro-environments with higher or lower temperatures than around the thermometer. These can be used to the gardener’s advantage if they are known about, and are found close to the glass, near the ventilation area and other places that have less sunlight, or excessive sunlight.
