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The ideal temperature and humidity for a grow tent

Ideal temp and humidity for grow tent

The ideal temp and humidity for grow tents is an extremely important component of growing indoors. This is something that novice growers may neglect to consider, however, it is essential for growing cannabis indoors.

Here, we will look at adjusting, amending, and figuring out the optimum grow room temp and humidity.

Why the ideal temp and humidity for a grow tent matters

Temperature and humidity play a critical role in the growth rate and the returns you get from your cannabis. For starters, the temperature experienced by your Cannabis plants dictates the color of the leaves and buds. Depending on the strain’s genetics, the cannabis temperature level can either suppress or bring out the pinks, blues, or purple colors.

Furthermore, the cannabis temperature influences the growth pattern of the plants. It can either slow or speed up the growth speed, so you should adjust the temperatures accordingly.

Temperature plays a crucial role in the drying and curing processes, which is the other reason to ensure optimum temperature levels, not to forget that heat affects humidity levels.

On the other hand, when you think of humidity for Cannabis, consider how the plants absorb air from the surroundings. As they respire, the plants naturally lose the water retained in the foliage. If the air is dry, they are likely to lose more water than they can absorb, slowing down their growth rates. The optimum humidity levels allow plants to open their pores correctly, emit more carbon dioxide and flourish.

How temperature affects Cannabis

Even though we are talking about the ideal temp and humidity for a grow tent, it’s important to look at the impacts of both attributes individually.

Temperature too high

Although cannabis plants cannot quickly die from too much heat, the condition slows down the growth rate of the plants. Too high temperature during the flowering stage slows down bud growth and may make the buds loose.

Cannabis plants grown in an overly hot environment are susceptible to root rot, mildew, nutrient burn, and spider mites. The plants are also likely to stretch and wilt due to a lack of enough oxygen.

Temperature too low

Frigid temperatures slow down the cannabis plants’ growth. Cold tends to compromise growth and could even shock and kill the plants.

Some plants may not show any adverse signs, but eventually, they fail to yield as expected.

Plants grown in cold temperatures are susceptible to mold. In some cases, the condition may cause over-purpling of leaves, which compromises photosynthesis.

What impact does humidity have on cannabis?

So, now that we have covered the temperature, time to look at humidity.

High humidity

Too much humidity puts plants at risk of bud rot. Moreover, high humidity levels for cannabis may cause disease as excess moisture buildup in foliage, thus creating a suitable environment for bacteria to thrive.

Moisture on grass
Drips of water hanging from the grass in the field because the air moisture is high

Low Humidity 

Excessively dry air makes it hard for the plants to respire. The reason is that the pores will not open, making it hard for the plants to emit carbon dioxide. This hinders photosynthesis.

What is the ideal cannabis temperature?

The suitable temperature level depends on the plant’s stage of growth.

  • Seedling

The ideal seedling temperature ranges from 20 to 25 degrees Celsius.

  • Veg

Vegetative and post vegetative states require temperature levels of 25 to 28 degrees Celsius.

  • Flowering stage

The suitable flowering temperature ranges from 18 to 25 degrees Celsius.

The relationship between temperature and humidity – VPD

Air humidity levels are dependent on the temperatures. The excess water may fork films or dew over leaves if the air is too saturated with moisture. This causes bud rot and mildew, not to forget that it slows down plant growth.

The reason we say it’s important to figure out the ideal temp and humidity for a grow tent instead of each factor individually is that they’re definitely related.

Considering how closely related temperatures and humidity are, you can quickly overcome one problem by solving 5je other. For instance, warm air may mean more humidity in the air due to evaporation. This is where Vapor Pressure Deficit, abbreviated as VPD, comes in to help you measure temperature and humidity.

The ideal VPD levels should range from 0.45 kPa to 1.25kPa. Most cannabis plants thrive best at VPD levels of 0.8kPa to 0.95kPa.

Note that if the grow tent is too hot and dry, VPD will be higher than the ideal level, causing the plants to have slow growth. Similarly, if the room is too cold and humid, VPD will be lower than optimal, and plants are at risk of fungi and mold growth.

What is the ideal humidity level?

Again, the ideal humidity in the grow room differs in different cycles.

  • Seedling stage

The ideal humidity in the grow room for seedlings ranges from 65-80%.

  • Veg stage

Humidity for veg cannabis ranges between 55 – 70%.

How to control temperature and humidity in a grow tent

Here is a step by step guide on how to control temperature and humidity in a grow tent;

1.  Have the right tools

You will need a thermometer and hygrometer to help you measure the temperature and humidity of cannabis.

2.  Lower temperature levels

To maintain the best temperature and humidity for cannabis, ensure temp is not too high. If you notice the temperature is above the ideal level;

  • Increase the airflow and air exchange in the grow tent
  • Turn off the lights during the day
  • If you are using High-Pressure Sodium Lights, get an incredible tube
  • Install AC in the grow tent

3.  Increasing temperature

If the temperatures are below the optimum levels;

  • Get a larger grow light for best temp and humidity for cananbis
  • You may add a heating mat to the grow tent
  • Use a tent heater and ensure it comes with a thermostat for settings
  • Lower Humidity

If the humidity for growing cannabis is too high, you may;

  • Upgrade your airflow fans to increase the amount of cool air supply in the tent
  • Water the plants as soon as you switch on the lights
  • Invest in a quality dehumidifier to achieve the best humidity for growing cannabis

5.  Increasing humidity

To increase moisture and achieve ideal humidity for growing cannabis;

  • Mist the air with a spray bottle for temporary effect
  • Keep the soil moist but not overly wet
  • Hang damp clothes or towel in the grow tent
  • Invest in a quality humidifier with a water reservoir

The strain makes a difference

When trying to achieve the best seedling temperature and humidity, or the ideal conditions for flowering, remember that the requirements differ from one strain to the other. Take your time to learn the ideal temp and humidity for grow tents when using different strains before jumping right on it.

For example, pure sativas, like these Durban Poison seeds will have a different ideal temp and humidity in a grow tent than Strawberry Kush seeds, which are indica-dominant.

Picture of Taylor Christianson

Taylor Christianson

Taylor is an indoor expert. Through their writing, they offer a masterclass on growing cannabis indoors, maintaining a productive growing environment, and guiding growers through all the stages of growth both indoors and outdoors. Combining multiple fields of expertise allows for Taylor to give in-depth insights into overall cannabis growing. About this Author

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