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Growing Tips – Humidity

Apr 12, 2020
Humidity Problems

How to Keep Your Grow Room from Getting Too Hot and Humid

Over the past ten years, many states and countries have legalized the sale and consumption of medicinal and recreational cannabis. Even without nationwide legalization, the United States marijuana market reached a value of more than $9 billion back in 2017. It is expected to approach $47 billion by 2027.

Investors are scrambling to get into the cannabis business, as they see it as a safe long-term bet. Many of these investors are directing their efforts toward marijuana dispensaries instead of growers. As dispensaries grow in size and numbers, consumers’ expectations increase as well. Dispensaries are looking for consistent selection and quality products, which means growers are under more pressure.

Grow room humidity and temperature control will ensure the quality and consistency of a cannabis crop, and in this guide, you’ll learn how to regulate these two all-important factors.

Let’s Get Started

How can growers provide consistent crops that build their brand? It’s all about the product you’re growing, where it’s grown, and the conditions under which it is grown. In the sections below, we will discuss how to create the ideal growth environment through temperature and humidity controls. If you grow plants starting with authentic genetics from i49seed bank, there is no reason you can’t be growing the best auto bruce banner buds on the market!

To begin, relative humidity is a measurement of how much water vapor the grow room’s air can hold at a predetermined temperature. Warm air holds more water than cold air does, so the warmer the grow room is, the higher the humidity reading will be.

As most growers already know, after selecting a substrate (the materials upon which the plants are grown), the strains of marijuana to be cultivated, the lighting, nutrients, and watering methods, the most crucial element of a successful grow room is humidity and temperature management.

Cannabis plants need different things at each stage in their life cycle. With the proper equipment, it’s easy to manage these needs. As long as you’re focusing on keeping everything within a consistent, appropriate range, your plants will grow healthy and strong.

To start, purchase a thermometer and a hygrometer. With these simple tools, it’s easy to accurately measure and change temperature and humidity conditions to achieve consistent, repeatable, and reliable quality levels with each crop.

Keeping Humidity and Temperature at the Right Level for Each Stage in the Cannabis Plant Life Cycle

In the seedling stage:

  • Keep clones and seedlings at a high humidity level of 65-70%.
  • When the lights are on, keep the temperature between 68 and 77 degrees. With the lights off, temps should be eight to nine degrees lower.

Increased humidity allows seedlings to absorb water through their leaves as their roots develop.

During the vegetative stage:

  • The humidity level may be lowered by up to 5% per week until it’s 40-70%.
  • The temperature may be raised slightly.
  • With the lights on, temps should be 71-82 degrees; during periods of darkness, the temperature should be eight to nine degrees lower.

As the plant’s roots are more fully developed, they can absorb most of their water in that way. The plants will be cooled via leaf-based evaporation.

During the flowering phase:

  • The humidity level should be kept between 40 and 50%.
  • Humidity should never be above 60%.
  • With the lights on, keep the temperature between 68 and 79 degrees Fahrenheit.

During the later part of the flowering phase, certain factors may affect the crop’s yield, appearance, and flavor. To avoid these effects, bring the humidity level down to 30-40%. Lower the daytime temperature and increase the temperature difference at night. With the lights on, keep the grow room at 64-75 degrees. With the lights off, the temperature should be nine to 18 degrees lower.

Adjusting Temperature and Humidity Levels

Depending on the lighting chosen for the grow room, the season in which the crop is grown, the quality and quantity of outdoor air being brought in, and other factors, controlling humidity and temperature in the grow room is one of the toughest challenges a cannabis cultivator faces. In the sections below, we’ll discuss a few ways to help you keep your grow room humidity in check.

To lower humidity levels:

  • Run a tube vent at a higher velocity or consider upgrading the fans for better airflow. This goes for air exits in tented areas as well as the rooms in which those tents are placed.
  • Water the plants as soon as the lights are turned on. The grow room will be at its coolest and the quick absorption of water will help to decrease humidity.
  • For greater consistency, purchase a humidifier of the right size. A small unit won’t have a large enough tank to keep up with the room’s demand.

To lower the temperature:

  • Increase total air exchange and airflow in the grow room.
  • Keep the lights off during the day and turn them on at night.
  • When using HPS (high pressure sodium) lights, consider adding cool tubes.
  • Install an AC unit to lower the temperature and decrease humidity.

To increase humidity levels:

  • Mist the plants with a spray bottle for a temporary boost.
  • Keep the soil surface moist but not saturated.
  • Hang wet cloths in the grow room or add a few open containers of water.
  • Add a humidifier for the most consistent results.

To raise the temperature:

  • Upgrade to larger grow lights. The more watts a light has, the more heat it puts out.
  • Put a heating pad at the bottom of the grow room or tent.
  • Use a space heater with a thermostat.

Safeguarding Your Cannabis Investment

Though it’s exciting to see the results of your harvesting efforts, the work isn’t quite done yet. Proper crop processing minimizes the chances of damage and waste. Curing and drying are an essential step in reducing mold contamination and improving the taste of the final product.


Along with the need for humidity and temperature controls during the cultivation process, it’s equally important to monitor humidity levels during drying. If the curing space is too humid, you’ll be left with moldy buds (and no one wants that.) When you look for marijuana seeds for sale, some may even be advertised as mold resistant – but you still need to be cautious during the drying and curing stage to keep fresh air moving through the room.

Wet or Dry Trimming?

Curing breaks down the chlorophyll remaining in a plant, mellowing the taste of the product. No one wants harsh buds, and proper curing procedures can also enhance a crop’s shelf life. That’s an important quality in cannabis, which comes without preservatives.

  • In wet trimming, the plants are trimmed as soon as they’re ripe. Remove branches one by one and use sharp shears to trim excess material. As soon as the branches are cut, drying can begin. The buds will be wet and sticky, which is both an indicator of quality and a potential breeding ground for mold and other contaminants. Wet trimming offers greater quality assurance and control, and it allows growers to collect sugar leaves which can be made into edibles.
  • The dry trimming technique is typically reserved for large-scale cultivators with little processing time. It involves cutting branches and hanging them from drying lines. Once they’re dry, the branches are trimmed and then processed. It’s much harder to attain the neatness and simplicity of wet trimming as the sugar leaves will curl inward when drying. Handling dried buds during the process may lead to the loss of resin crystals.

Conditions in the Drying Room

No matter which method a grower uses to trim their product, it’s crucial to keep the drying room’s conditions within narrow parameters. Strive for a dark, cool environment with a temperature between 59 and 71 degrees and a humidity level close to 50%. Even after the plants have grown, you’ll still have to focus on humidity and temperature.

Drying the Product

If you’re using the wet trimming approach, the plants must be spread over a wide area. Aeration is critical, and growers should avoid setting flowers on newspaper or cardboard as uneven drying may occur. Netted or mesh drying racks are preferred because they allow for even airflow on all sides. Be sure to leave enough space to spread the crop evenly for the most favorable results.

Though it may be tempting to accelerate the drying process, it’s best to take a steady and slow approach. Rushing through the drying process and exposing the flowers to high temps will diminish the crop’s quality and flavor. If you’re growing cannabis to sell to a dispensary, that’s not a very good way to build a solid reputation. Whether you start with regular, feminized, or dwarf autoflower seeds USA, we care about the outcome of your crop and want to make sure the end product is the most enjoyable smoke possible!

In Closing

Cannabis growers face numerous challenges, with humidity and temperature control being two of the most significant. With the following equipment, it’s possible to keep levels optimal.

  • AC units
  • Dehumidifiers
  • Humidifiers
  • Portable heaters
  • Thermometers and hygrometers to measure temperature and humidity levels

Growers should check on their crops at least twice per week and cut flowers should grow noticeably drier with every check. You’ll know the buds are cured when they easily snap with no stringiness. If the buds bend when twisted, there’s still moisture present and they’re not ready to put into jars or other packaging. With the tips, tricks, and advice in this guide, as well as high-quality cannabis seeds from, it’s possible to grow a top-quality crop for commercial, medicinal, or recreational use.

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