All You Need to Know About Humidity Control when Growing Indoor Cannabis

All You Need to Know About Humidity Control when Growing Indoor Cannabis

Ideal Relative Humidity Levels For Each Of The Cannabis Plant Growth Stages.

Seedling Stage – 60-70% Relative Humidity

  • During the seedling stage, the cannabis plant needs the most moisture.
  • This is true for young marijuana plant cuttings and clones.
  • A young cannabis plant or a seedling has underdeveloped roots that have a low capacity to soak moisture from the soil for hydrating the plant.
  • High relative humidity levels support the young plant in absorbing moisture from the surrounding air through its leaves, and it stays hydrated despite the roots’ inability to absorb moisture.
  • Moisture content can be increased by decreasing the air circulation in low humidity.
  • Humidifiers are needed for increasing the humidity levels.
  • Humidity levels of the seedlings need to be checked often and very minutely for providing enough water.
  • Young plants soak in a lot of water and get rapidly dried.

Mid and Late Vegetative Stage – 45-85% Relative Humidity

  • The marijuana root system gets developed quickly.
  • The root system hydrates the plant well, enhancing its growth and strength.
  • You can decrease the humidity levels during the late vegetative phase as the leaves and root systems develop well by then.

Early Flowering Phase – 40-55% Relative Humidity

  • Once the plant enters the blooming phase, you can lower the humidity levels.
  • The plant becomes susceptible to a mold or fungus infection if the moisture level increases more than 40-55%.
  • Lower humidity levels would keep the dense, tightly packed cannabis flowers dry and prevent any probable infestation.
  • The air circulation in the growing area can be increased to reduce the relative humidity to the needed level.

Late Flowering Phase-25-40% Relative Humidity

  • The late flowering stage of the cannabis plant needs the lowest levels of humidity compared to all its growth phases.
  • The buds start becoming fatter and denser at this stage.
  • Lower humidity will support you in ensuring that the buds don’t get infested with mold or fungus during the late flowering phase.
  • You can maximize the ventilation and keep the humidity levels at an optimum 25-40% to provide the right growing conditions in this stage.
  • You can also reduce moisture content by watering the plant when it is in the dark phase.
  • Grow area temperature can also be reduced to support the plant during this phase.
  • Reducing the moisture and temperature level will increase the quality and quantity of your yield.

Equipment That Will Help You Provide Correct Humidity Level

 Humidity Meters Or Hygrometers

  • To monitor the moisture levels in the growing area, use a hygrometer or a simple humidity meter.
  • Some humidity meters monitor the co2 levels, and the temperature in the grow room.


  • Humidifiers work best in a large growing space.
  • Hanging fluffy towels saturated with water from a hanger will be enough to increase the humidity in a small or medium-sized grow room.
  • In large commercial cannabis cultivation, automated humidifiers are used to adjust and monitor the humidity.
  • These automated humidifiers minimize guesswork and labor from the process.


  • Grow room dehumidifiers can be used to decrease the level of humidity in your growing area.
  • However, this investment will be a pricey one.

Final Thoughts

You might not have given much thought to humidity levels before this, but you should do that to maximize the yield and protect your plants from mold and fungus infestations. Proper humidity levels can also save your plant from bud rot or root rot.

Though the above guidelines are useful, you must understand what a particular strain needs when you are purchasing marijuana seeds. You can get all this information if you buy your seeds from a top online seed bank like i49. You can choose a top-quality strain with stabilized genetics from this site, and you will also be able to decide if the particular strain meets your requirement.

When you provide your cannabis plants with the optimum levels of humidity that are required in each of their growth phases, the plants will stay well and provide you with maximum yield.

I end this with a wish for you. May you enjoy amazing, fat, dense buds dripping with trichomes and that taste and smell divine. Enjoy your growing adventure, and keep learning as you go. Enjoy! Goodbye