Indoor Cannabis Humidity and TemperatureGianenzo Sapgnuolo
Humidity Horrors and Temper Tantrums
If you can’t get your humidity and temperature under control, expect something to go wrong at some stage. We often overlook these critical elements of a grow when we focus too heavily on other aspects. Stable temperature and humidity are actually beneficial and will improve your grow.
Temperature and humidity are closely related, humidity refers to how “wet” your air is, the more water vapor in the air the more humid it is. Science class taught us that hot air contains more moisture than cold air. It is vital to be able to replace warm, humid and stale air with cool, fresh and dry air during your grow.
Different Stages, Different Strategies
Cannabis grows are split up into four stages, during each stage, the developing plant requires a specific humidity and temperature. Keeping humidity and temperature constant during these different stages is key and will ensure healthy, optimal development and larger yields.
Monitoring the changes in humidity and temperature can be done with the use of a hygrometer and thermometer. Now that we can monitor our highs and lows during the day, if we see anything unusual we should aim to correct it.
During this stage the root system is not well established for water uptake. For this reason, seedlings thrive in a high humidity environment of 65-70%, with ambient temperatures between 20-25°C. Seedlings are able to absorb moisture through their leaves, the more moisture in the air the better.
The root system of the plant is now established, absorbing water from the ground. Humidity can be reduced during this stage and temperatures can be raised slightly to 22-28°C. Remember that at higher temperatures more humidity can result.
Humidity and temperature in this stage are critical to monitor, aim for 40-50% humidity and never exceed 60%, lower temperatures by 2-4°C and avoid temperatures above 26°C.
Flowering, 1-2 weeks before harvest:
Your buds are almost ready, reduce the humidity as much as possible (30-40%). Molds and rot start to set in during this time if temperature and humidity are too high. Reducing temperature by a further 2-4°C in the day and increasing night temperatures by a couple degrees can improve flavors and appearance.
How to Climate Control?
Knowing where to keep your temperature and humidity levels is one thing, but what happens when everything goes out of balance? Depending on your local environment, you may have to raise or lower the humidity and temperature for your grow.
Increase airflow with a powerful inline fan to draw out old “wet” air and replace it with fresh, “dry” outside air.
Water plants as the lights turn on while temperatures are low to reduce humidity and allow your plants to absorb the water as they wake up.
Invest in a dehumidifier that will be effective in your grow space.
Add moisture to the air with a spray bottle or foliage feed.
Purchase a humidifier that is suitable for your grow room size.
Add containers of water that will evaporate as temperatures increase.
Do not restrict the airflow of new air, instead try to add more warm air.
Increase airflow of fresh “dry” cool outside air and extraction of warm “wet” air using an inline fan suited for your grow size.
Turn lights on during the coolest parts of the day and turn them off for the warmest parts.
LED lights produce less heat than HPS.
Install a air conditioning unit, they can also lower humidity.
Switch to an HPS bulb instead of LED’s.
Run a portable heater/heating mat inside your grow tent.
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