cannabis grow room temp and humidity

As you probably already know, after choosing a substrate (the material you’ll be growing your plants in/on), the strain(s) of cannabis you’ll be growing, lights, watering mechanisms and nutrients needed, the most important element of your day-to-day operation will be managing temperature and humidity.

To get started, you’ll want to buy a hygrometer and a thermometer. With these tools, you can accurately monitor and then alter humidity and temperature conditions in an attempt to strive for repeatable quality levels time and time again.

You may be tempted to speed up the drying process but it has been shown that slow and steady wins the race. Rushing the process and exposing your crop to high temperatures will almost certainly reduce the quality, and result in diminished flavor and even potentially a “poor and uncomfortable high.” Good luck explaining that to your investors or to a discerning dispensary that has numerous growers vying for their shelf space.

Vegetation Period.

“Wet trimming” involves trimming as soon as plants are ripe. Remove individual branches and proceed to use sharp scissors or shears to precisely trim excess plant matter. As soon as the plants are cut down, the drying process begins. What’s immediately noticeable is how sticky and wet the buds are. While this is an excellent indicator of potential quality, it’s also a breeding ground for contaminants. Buds left in this state will almost certainly be ruined so it is best to act quickly to begin a controlled drying process.

This technique is usually reserved for growers with a large amount of plant matter and little time to process it. This involves cutting off branches and hanging them whole from drying lines. Once the plants are dry, they are then trimmed and processed. It is more difficult to achieve the neatness of a wet trim as sugar leaves will curl in toward the buds while drying. The agitation of handling a dried bud during trimming can also result in the loss of potent resin crystals.

Too much humidity in your curing space and you might be left with perfectly grown, but moldy cannabis. Nobody wants that; neither the individual user nor the dispensary buyer. Moldy cannabis is easily the fastest way to ruin your reputation as a reliable grower of high-quality buds.

Investors are flocking to the marijuana industry, seeing it as one of the safest long-term bets in recent history. Many of them are directing their investments toward dispensaries rather than growers, according to Scott Greiper, president of Viridian Capital Partners.

Widely regarded as the preferred method, “wet trimming” offers the most control and quality assurance. It also has the added benefit of allowing you to collect the “sugar leaves” which contain lower cannabinoid levels and can be stored separately to be processed into edibles at a later time. Remember that “High THC; low Cannabinoid level oil” states list from before? This is where that product comes from.

On behalf of their customers, dispensaries are looking for consistent quality and a range of products. So while the opportunity to run a lucrative and stable growing business has increased dramatically, there is more and more pressure for growers to produce a consistently high-quality product in order to turn increased demand into increased dollars.

Flowering Period.

Again borrowing from Royal Queen Seeds expertise, here’s a how-to on drying your valuable crop:

The curing process breaks down chlorophyll remaining in the plant, resulting in a less-harsh taste. Remember: harsh buds are not quality buds. These procedures can enhance the shelf-life of a crop, which is highly important with a product like cannabis that isn’t afforded the addition of preservatives.

Pure n Natural Systems specializes in the sale of commercial and industrial humidifiers, dehumidifiers, drying fans, air movers, and portable heating and cooling solutions. We have the equipment you need to make your growing operation a consistent success. And as we’ve already discussed, consistency is king.

On top of the need for specific temperature and humidity controls throughout the growing process, it’s worth mentioning that humidity level during the drying process is equally important to the quality of the final product.

Dry Trimming.

Depending on your lighting solution, season a specific crop is grown in (assuming year-around production), the outdoor air vented in (as it will vary in temperature and its own relative humidity), controlling temperature and humidity in your growing space will be one of the tougher challenges you will face on a day-to-day basis.

That said, we are not experts in growing specifics or in the design of custom-growing spaces.

Whichever method you choose for trimming your product, suitable conditions for your drying room are important. You’ll want a cool, dark environment with temperatures in the range of 59-71°F and humidity at or near 50% . Yes, even after the growing process is completed, you still need to be concerned with temperature and humidity.

As the roots are now more developed, they’re able to perform most of the needed water uptake with evaporation through the leaves now cooling the plants.

If you opt to use the wet trimming method, you will need to spread them out across a large surface area. Aeration is important so you’ll want to avoid setting the flowers on a surface like cardboard or newspaper as the buds will dry unevenly. Wire mesh or netted drying racks are more beneficial. This allows airflow to reach all sides and lessen the chance of moist air pockets. Make sure to allow yourself enough space to spread your crop out evenly with a small amount of space between buds for the best results.

Nutrient Problems.

Air Conditioner (some are portable, some ACs fit in your window) – tends to lower humidity (in addition to cooling the air)

Monitor temperature & humidity in your grow room!

Bud rot or mold is – in my opinion – one of the worst pains a grower can experience as a result of poor humidity management. Imagine harvesting a huge, dense main cola from your plant only to see the insides are totally white or brown with mold. Buds in this condition are unusable and 100% should be thrown away.

Below is a quick reference for the major stages of the cannabis life cycle in regards to the relative humidity you are aiming for. We’ll go through them all in more detail.

40-50% RH (a little less humidity helps protect plants from mold – during the last few weeks of flowering, a lower RH can possibly increase resin production as buds approach harvest)

The ideas is to create a comfortably warm environment that mimics springtime or summer.

Humidity for flowering plants.

Put the “outdoor” module in your grow tent or box.

Here’s a really simple solution that lets you check your temperature and humidity of your grow room in real-time, even if you’re not at home!

Effects of Poor Humidity Management.

Additionally, after your plants start making buds in the flowering stage and get close to harvest, you can manipulate the humidity of your grow area to get your plants to produce more resin (trichomes/glitter which contain THC and other cannabinoids) while preventing plants from being attacked by mold. High humidity can sometimes cause mold or bud rot – a grower’s worst nightmare for those fat, dense main colas.

It moistens the air while keeping the temperature down, which can also be a problem in Denver.

But the roots aren’t the only way your plant gets water. Leaves can actually pull water vapor directly out of the air, and higher humidity in the air allows the leaves to get more water to the plant if needed. Until your plant has fully developed roots, low levels of humidity in the air can cause growth to be slower.

But controlling humidity isn’t just about prevention…having the right humidity encourages strong, healthy, leafy plants with vigorous growth. In fact, growing with DWC (Deep Water Culture) / Bubbleponics during vegetation with the correct humidity can actually turn into a struggle to tame out-of-control plant growth!

White Powdery Mildew.

If you want to grow sticky, high-potency buds, your cannabis will demand attention to its many needs.

I like the Ambient Weather WS-07 Wireless Thermo-Hygrometer because it lets you remotely check the temperature and humidity from another room (don’t forget to get 6 AAA batteries).

Buds that have been professionally dried and cured are more potent, denser, smoother to smoke, look better, and have that coveted “sticky-icky” feeling.

However, to get most cannabis plants to start making buds, you need to give them at least 12 hours of complete darkness every night, which means grow lights need to be off for 12 hours/day. For some growers in a wintry climate, a 12-hour dark period (even during the day) will send the temperature plummeting too low.

Relative Humidity – Temperature has a significant effect on the relative humidity of your grow area.

Preference: Comfortable Room Temperature or Slightly Warmer 70-85°F (20-30°C) – High humidity preferred (60-80%)

Drying & Curing – Temperature is incredibly vital to the drying & curing process. A professional dry/cure is one of the most significant factors when it comes to producing top-shelf buds.

7 Essential Concepts About Temperature Control.

Air Conditioner – (some are portable, some ACs fit in your window) – in addition to cooling the air, an AC will also tend to lower the relative humidity of the air. To be effective, and AC must be able to exhaust hot air outside the house, just like hot grow lights. If the air outside the grow tent is already too warm, you will need to get an AC to pre-cool the air before it enters the grow tent. No matter how strong your exhaust system, it won’t be able to bring the temperature lower than your ambient room temperature. If you need to lower the ambient room temperature, you’re going to need a way to cool the air, and air conditioners are hands-down the most effective way to cool your air.

Why Is temperature critical when growing cannabis? Can cannabis stand freezing temps? What happens if your grow room gets too hot?

Maintaining slightly cooler night temperatures (in the specified range) tends to promote the fastest and healthiest vegetative growing for cannabis plants.

CFL grow lights have earned a reputation for being very low heat. And, indeed, you can successfully grow a cannabis plant under just a few CFLs, and they won’t give off much heat.

Chart – optimal temperature for growing cannabis plants.

Step 3: Correct Too-High or Too-Low Temps (explained)

Give plants colder temperatures at night, especially towards the end of the flowering stage.

That’s why it’s easier to cool an equivalent amount of HIDs compared to CFLs.

Learn more about how to professionally dry & cure your buds here: https://www.growweedeasy.com/how-to-cure-buds.

Temperature & Humidity Adjustment Cheat Sheet.

The temperature in the flowering stage is too important to ignore. That’s because keeping temps low during the flowering stage will help your plants produce the most potent, dense, smelly, and trichome-covered buds as possible.

Change the Light Schedule: If you’re in a situation where the temperature is climbing too high at specific parts of the day, then you can change your light schedule so that your grow lights are off during the hottest part of the day. For example, in the vegetative stage, your plants need 18+ hours of light each day. If it gets too hot in the middle of the day, you could set your timer to turn your lights off for 6 hours during that part of the day. This strategy will not fix a major heat problem but can help alleviate symptoms of heat stress during a short hot spell or heatwave.

Proper temperature brings out colors and can increase bud quality.

When growing cannabis plants, relative humidity (RH) is just as important as the temperature of the air and is something you should pay attention to, especially if you notice that your grow room is dry or humid.

P reference: Avoid hot temps! 65-80°F (18-26°C) – Mid-to-Low humidity – Slightly cooler at night than during the day.

Wet or humid conditions can lead to bud rot.

In the heat, cannabis is also more susceptible to many problems, including spider mites, white powdery mildew (especially if it gets humid, too), root rot, nutrient burn (from increased water transpiration), increased stretching, wilting due to root oxygen deprivation, and reduced “smelliness” of buds (as terpenes can burn away at higher temps).

MH/HPS/LEC grow lights are known for using a lot of electricity and producing a lot of heat. And while that’s true for the bigger models of HID lights, I think a lot of growers overestimate how much heat will be produced by the smaller HID models .

Unfortunately, higher temperatures during the flowering stage can cause plant problems and slowed bud growth. It can also cause terpenes and potency to evaporate into the air.

More About the Upper Limits of Temperature.

If the air is too cool and humid (low VPD), plants grow slowly and are prone to problems with mold or fungus.

Colder temps and significant temperature fluctuations contribute to the over-purpling of leaves and can also reduce photosynthesis.

If it’s too cold in your grow room, sometimes you have additional options besides just getting a heater, such as getting a stronger/hotter grow light or using extra insulation to contain the heat of the grow lights you do have.