What is the impact of excessive heat on indoor grow rooms?

 Grow in Australia anywhere north of Tasmania and excess heat in your grow room is a common problem for most of the year unless blessed with air conditioning. What do we mean by excess heat? Every gardener should know the parameters of their gardens at differing stages of a plant’s development and any temperatures over these parameters are considered excess.

Before tackling subjects like Vapor Pressure Deficit or Customizable light spectrums, growers need to identify and rectify excess heat issues in order to move forward. Even the best irrigated and high-tech lighting schedules won’t save you from problems caused by excess heat.

If you don’t know a gardens heat or temperature parameters, then how do you know if its too hot or cold? This is basic growing knowledge 101. Any temperature higher than 28 Degrees is problematic unless using Co2 and this will usually only allow a grower to push the limits to 30 -33 deg Celsius if all other environmental factors are within range or even perfect. Higher temperatures usually promote a drier environment or serve to lower relative humidity. If the heat doesn’t shut your gardens lungs down, then a dry environment will.

Stomata are a plants version of human lungs or at least that’s the best way to describe Stomata to someone who is just now heard the word and it is how plants breathe or respire. Before visible signs of burnt leaves or dry brown flowers a plants respiration slows then stops by closing the stomata and when this happens your plants shut down and go into survival mode literally.

They will only start normal respiration processes when conditions return more favorable. If the plant spends too much time in survival mode, then it’s not producing and susceptible to pests and disease as well producing inferior quality and yields. Smaller thinner up curled leaves at the canopy and noticeable decrease in plant vigor are first signs of extended heat stress. Also, a noticeable decrease in water / nutrient uptake is likely as the plant is just surviving and not producing.

Source: The Grow Shop