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I am growing some tomatoes in pots in a toy greenhouse. I've put a thermometer/ humidity meter inside.

The relative humidity changes from around 55% to 75%, and correspond to highest temperature of 26 Celsius (79 °F) and lowest around 17 °C (63 °F).

Both temperature and relative humidity are completely normal, but do plants prefer these changes? By which I mean, do the tomato greenhouse pros try to maintain a constant temperature and relative humidity, in order to maximize crop?

  • If there is anyway to provide stability in their environment that would be best. Constant is best...unless one gets to the point they want reproductive growth. The way to stimulate more fruit is by shortening the daylight hours, reducing the nitrogen. – stormy May 8 '17 at 4:30
  • The temperature range is perfect. Humidity is high. Do you have MAJOR fans blowing air so much so that you are able to see the tomato leaves 'moving' in the 'wind'? Any way to pump fresh air in, Pull air out...fungus will haunt you with the garden soil in your pots. Just remember 9 parts H20 to one part milk. Truly a wonderful help with powdery mildew. Bamboo gave us this formula and it works. – stormy May 8 '17 at 4:35
  • Thank. High humidity? I've looked the optimal range, and it goes waaay to the 90%. Although, you can't get any fruit if the plants die of mildew... The greenhouse area is connected to the house, and the doors (big doors) are wide open. We have air circulation installed in the house, so I guess greenhouse air also circulates. But no, no fans on anything. – sanjihan May 8 '17 at 8:26
  • I'm not sure about for maximizing your greenhouse harvest, but temperature and humidity changes between day and night are perfectly normal outdoors, outside of a greenhouse, and tomatoes do fine in many of those conditions. In my area, it's cooler and more humid at night than in the day. It seems like you'd want it drier at night, since darkness and humidity may favor fungi, but I really can't say it's better offhand (there's likely a good reason for the natural way). I have noticed that under-watered plants can also be prone to fungal disease. So, the benefit of dryness may depend on things. – Shule May 9 '17 at 4:35

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