3R Lighting/ tutorial: Hydroponics, Temperature, and Humidity

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3R Lighting Tutorial: Temperature & Humidity

Q: What is the best temperature and humidity for growing?
A: One of the great things about America is that everyone can have his or her own opinion--and everyone can be right.

Temperature and humidity in growing plants are what are called variables in Scientific Terms. For the rest of us, this means there is a pretty wide range that will encourage your plants to grow fairly well. It also means that changing one aspect of the plant's environment (or factor) can cause changes in some of the other growing conditions.Generally speaking, if you are comfortable with the temperature and humidity, so are your plants.

Q: Can we put some numbers on that?
Obviously, around 32 degrees F the plants will frost, and can die. Likewise at about 120 degrees F vegetables will start to cook. Most books give the optimum range at about 72 to 76 degrees F for the air temperature and about 65 to 70 degrees for the nutrient water temperature in hydroponics. These are targets, so your results may vary. Different types of plants sometimes grow better with different temperatures; some plants require some "chill time" to bloom.
One very large aspect of temperature is that temperature directly affects the relative humidity. It is called RELATIVE humidity because the amount of water evaporated into the air is measured RELATIVE to the temperature.

Q: OK, Einstein, how does this relativity work?
A: This relativity does not have anything to do with Einstein or your brother-in-law.
All this relativity means is that the hotter the air, the more water or moisture can be evaporated into the air. If you can visualize for minute a 5 gallon bucket of water evaporated into a room about 8 feet by 10 feet with an 8 foot ceiling at 100 degrees F, the humidity would be high, like a sauna. Now, imagine the room cooling down to 45 degrees F, the water would condense into droplets on the walls.

Q: So?
A: If there is a big temperature difference between daytime and nightime temperature, you can grow molds and fungus at night.
There can also be a wide variation of both temperature and humidity in different areas of the same room. Likewise, as the plants grow, they can change the conditions as well.