How To Raise The Humidity In A Grow Tent (Lower Also)

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    Why Would You Care About Too Low or Too High Humidity?

    Having an indoor garden can be quite complex. To succeed, you’ll have to learn everything from soil science to what nutrient solution is best for your plants. One thing that you should not forget is the grow tent humidity.

    You might wonder, why should growers care about controlling humidity? Read and you will find out, about the importance of the correct humidity, what equipment is needed to control it, and also ways to lower or raise your grow room humidity.

    Note To Non-cannabis. So, the information is geared toward growing weed. As a result, other than the importance of grow space humidity being at the correct levels and the equipment needed, the information here may be wrong for houseplants.

    What is Humidity?

    Relative Humidity Level (“RH“) is the percentage of moisture in the air in relation to how much water the air is able to hold. All you need to remember is that warm air is able to hold more moisture than cold air can.  Humidity and RH will be used interchangeably in this post.

    Importance  OfHumidity For Indoor Plants

    Humidity at the right levels means your plants will utilize water and nutrients more efficiently. However, if the humidity level is too low or too high, there will be problems.

    With too high humidity your cannabis plants will go into defense mode that will cause havoc on the stomata’s transpiration. (Stomata are the holes or pores in a plant’s leaves or stems that take in the water, and transpiration is when a plant releases the water through the stomata)

    This will, because of lack of water, result in stunted plant growth. On the other hand, with too low humidity, a growing plant will end up looking sickly.

    What is the Optimal Humidity For A Grow Room?

    Room temperature and humidity percentage are critical when it comes to the grow room humidity. So, you need the correct figures for both.

    The following recommendations, depending upon factors like the strain, may vary. If you are growing an exotic cannabis strain or trying something new, contact the nursery or do extra research to find out if you should use another standard

    There are a few approaches to what the humidity percentage should be for your grow room. With all of these approaches, the humidity starts out high and then gets lower as the flowering and late flowering cannabis growth stages are approached.

    The general rule of thumb is that, for young plants, you start out at 70% humidity, and then it is reduced by 5% until you get to an approximately 40% humidity level.

    The recommended starting and ending humidity percentages vary between different authorities. However, for clones, 60% or more relative humidity will be too high and you should not go below 30% relative humidity when you reach the late flowering growth stage.

    Recommended Temperature

    The optimal, grow temperature largely depends upon the age of the plants.

    Clones-For Clones or very new plants the room should be between 74 to 77 degrees all day and all night.

    Vegetative Growth Stage-75 to 85 degrees during the day and 65 to 75 degrees at night.

    Flowering Stage-65 to 80 degrees for day and at night between 60 to 75 degrees.

    What is The Result of Poor Humidity Levels?

    Too low and too high RH levels can result in stunted growth, mildew, bud rot, and sickly looking cannabis plant. So, keeping your grow tent at optimal RH percentage is essential.

    The following are the damaging consequences that you can expect if RH is either too high or low.

    Too High

    Mildew and Mold-The biggest issue that you will encounter with too high humidity is that your plants will be more likely to get mildew (I.E, White Powdery Mildew”. Additionally, too much water in the air might result in the dreaded bud rot. Both bud rot and white powdery mildew are spread easily in a grow tent or grow room and if not taken care of ASAP, your entire crop can be ruined.

    Nutrients-Too high RH can also cause mayhem in a plant’s ability to fully absorb water vapor and other nutrients. The reason is that because of the excess moisture in the air a cannabis plant’s roots will ingest less or even no water through their roots.

    Too Low

    When the humidity is too low your plants will lose more water than they are able to regain via respiration. To deal with excessively dry air, your plants will close their stomata, which results in less water loss.

    Less water loss also means less carbon dioxide. And less carbon dioxide results in your plants having an overall limp and sickly look.

    RH Grow Room Equipment

    As stated earlier, the RH and temperature go hand in hand. So, you will need to purchase equipment that deals with both temperature and humidity control. Additionally, a proper ventilation system is also necessary. The necessary equipment is listed below and is readily available on Amazon.

    If you are a newbie grower or have not bought your grow light setup yet, you should consider buying a growing kit that would have most of the equipment listed below.


    • Hygrometer-The hygrometer measures the grow space humidity level. A Hygrometer ranges in price from under $10 to over $80.
    • Thermometer-of course this measures your growing area’s temperature.

    You can also purchase a combined hygrometer and thermometer, like the one listed below that is shown for example.

    ThermoPro TP50 Digital Hygrometer Indoor Thermometer Room Thermometer and Humidity Gauge with Temperature Humidity Monitor

    Dehumidifier-The grow room humidifier regulates RH by removing water vapors in the air and then releasing hotter air that has less moisture.

    VIVOSUN Small Space Mini Dehumidifier for Grow tent Closets Bathroom and Basement

    Air Conditioner– Obviously, the air conditioner helps you keep your grow space temperature at the optimum levels.

    COSTWAY Air Cooler and Heater, Compact Portable cooler with Fan Filter Humidifier Ice Crystal Box Remote Control, Evaporative Cooler and Heater for Indoor, Home Office Dorms

    Fan– The exhaust fan by improving the air circulation. It is especially helpful for lowering grow tent humidity.

    VIVOSUN 4 Inch 190 CFM Inline Fan with Speed Controller, 4 Inch Carbon Filter and 8 Feet of Ducting for Grow Tent Ventilation

    How To Raise And Lower Grow Tent Humidity

    Raising It-Using a humidifier is the most straightforward way for you to raise the humidity in your grow tent. If you don’t have a humidifier you will need to raise the temperature in your grow tent, as the higher the temperature the higher the RH percentage. A grow tent‘s temperature can be raised by adjusting the grow lights.

    Lowering Air Humdity– You can get a lower humidity level in your grow area by having a proper ventilation system. However, it will be simpler and you will get better results by using a grow room humidifier.

    Specifically, if you do not have a dehumidifier; to get lower humidity you will need to buy either more fans or more powerful fans.

    Final Thoughts

    Growing cannabis indoors can be quite a challenge. Knowing the correct lights to use, base nutrients, and also how to properly control humidity can get quite confusing. But, if you know what you are doing, you can grow weed in a perfect environment 365 days a year. So, if you learn how to control RH along with other indoor growing fundamentals you will be well rewarded.




    Top 10 Newbie Friendly Cannabis Seeds

    • Are you going to start growing for the first time?
    • Have you previously have had subpar growing results?
      If so, check out this list ASAP!
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