Temperature
An ideal temperature for your plants during daylight is 24°c to 28°c. A slightly higher temperature wouldn't be a disaster but too much over 30°c and you'll run into problems as the plant expends a lot of energy trying to keep itself cool and photosynthesis slows down resulting in underdeveloped flowers and fruits.At night the closer you can keep your plant temperature to your daytime temperature the better your plants will perform. If there is a big difference between these two temperatures your plants will stretch and grow quite spindly.
Nutrient temperature
An ideal temperature for your nutrients would be 18-20°c. Keeping nutrients and additives at a good temperature is important as chemical reactions within the solution increase or sometimes only happen when the water is at an appropriate temperature.Humidity
Humidity is not a key factor in growing but too low a humidity will slow growth and too high a humidity will cause pathogens to flourish. Humidity of 40% to 65% would be ideal, what you'll find is that humidity will rise throughout your growing cycle as the plants take on more water as they get bigger.PH
PH is critical to the plants ability to uptake nutrients and additives. In soil PH should be in the range 6.0 to 7.0, in hydroponics PH should be in the range 5.8 to 6.2.In recirculating hydroponics PH rises as the nutrient goes around the system so some schools of thought say you should start the PH lower at around 5.5 to allow for this. In a perfect world you would adjust the PH every day or so to 5.8-6.2 but if this isn't possible starting at a lower PH around 5.5 in recirculating systems would be a good idea.
Last Updated: June 19, 2008
