Growing Cannabis In Humid Environments: Effects And Stages of Growth

Imagine you’re playing football — you’d perform better when the pitch is dry and the weather is clear and cool. A warm, humid weather will only make you sweat a lot, tire you out a lot faster, and probably make you stink. If that’s what humidity can do to you, imagine what it can do to your cannabis plant.

Your cannabis plant won’t sweat, but humidity can wreak havoc on your cannabis plant if it’s not managed properly. High humidity can disrupt the plant’s photosynthesis, nutrient absorption, growth, and a lot more. So, if you are facing this challenge while growing cannabis in a humid region, here is everything you need to know to manage the humidity more effectively.  

Why is Humidity Important for Cannabis Plants?

Humidity is one of the most important aspects of growing cannabis plants, but what role does it play for your cannabis plant? Humidity is the amount of vapor present in the atmosphere, which in this case would be your grow room. The higher the vapor content, the higher the humidity levels.

Humidity for gardening purposes must be taken into account as relative humidity, which is directly related to the temperature in your grow room. Essentially, warmer air contains more moisture, so relative humidity is the moisture content in the atmosphere relative to the maximum moisture it can hold (saturation point). 

This relative humidity is essential for your plant’s transpiration, root function, nutrient absorption, cannabinoid and terpenoid development, and much more. Humidity is one of the main factors that make or break your cannabis plant’s growth and potency levels. 

So, when the humidity levels are ideal, your plant thrives. It can absorb all the nutrients it needs, transpire properly, and produce bushy buds flushed with trichomes. But how does it actually work?

When your cannabis plant produces energy by converting sugars during photosynthesis, it releases oxygen in the air via the stomata, and simultaneously, it also absorbs carbon dioxide from the air. This is where relative humidity comes into action — it dictates the amount of water/oxygen your cannabis plant will release into the air. 

If the humidity is too high, the water concentration gradient falls, so your plant fails to lose water as efficiently, which affects various processes within the plant, including its nutrient absorption rate. This is why ideal humidity levels are crucial for cannabis plants. 

How Does High Humidity Affect Cannabis Plants?

If you are living in a humid region, like a tropical coastal area, you need to especially worry about humidity because high humidity is arguably worse than low humidity. High humidity can have a drastic impact on your cannabis plant and its health. This is why you’ll find many farms using greenhouses in your region — to control the humidity levels of their plants. 

However, high humidity isn’t bad every time, especially when it comes to growing cannabis. It all depends on the stage of growth. We will go over this in the next section. At the same time, cannabis plants don’t like high humidity at all times. Here are some of the nasty outcomes of extremely high humidity for cannabis plants. 

Nutrient Deficiencies 

As mentioned earlier, the higher the humidity levels in the air, the less your cannabis plant loses water. And thanks to how the vascular system of your plant works, it can make it difficult for the roots to absorb the nutrients in this case. This can lead to nutrient deficiencies in your plant, which is never a good thing. This can lead to the leaves turning yellow or wilting, among other symptoms, and if it’s not addressed on time, it can further impact a plant's photosynthesis process, leading to stunted growth. 

Low Vigor

When your cannabis plant fails to produce enough energy and absorb the right amounts of nutrients, it loses its vigor. This can lead to the plant growing slower and smaller than expected. Eventually, this can lead to a much smaller yield than is typical for the strain you are growing. 

Bud Rot or Botrytis Cinerea 

One of the most fearsome crop killers for your cannabis plant comes when the humidity is too high; it’s bud rot. This fungal infection infects the dense core of your cannabis buds, beginning at the stem and spreading further outward. This makes bud rot even more dangerous because it’s hard to spot during its infancy — if you see bud rot, it’s already too late. 

Once bud rot takes hold of your cannabis buds, it will destroy the bud from within, turning it white and gray and eventually completely black. The bud will also begin to turn mushy and slimy. Even if there’s a small spot of bud rot mold on your bud, you need to toss it in the bin. 

However, bud rot not only affects one bud; it’s a fungal species, so it spreads its spores efficiently within the garden, and before you know it, your entire cannabis plant will be covered in moldy buds. If you are lucky, you can cut out the infected ones and let the remainder grow, but that’s rare. 

And don’t ever consider smoking a moldy bud — even if it has not turned slimy yet but has a slight fuzzy spot on it. Moldy buds can be harmful to your health and can lead to nausea, vomiting, lung infections, and for those who are allergic to mold, severe health complications, including death. 

Powdery Mildew

Another common crop killer that breeds in high-humidity environments is powdery mildew, which is very similar to bud rot but this one infects the entire plant, not just the buds. This infection usually develops in stagnant water, quickly spreading to your plant, and once it gets there, it starts multiplying quickly. 

Powdery mildew can be identified by its distinct white, fuzzy appearance, and like bud rot, even this infection can spread quickly to other plants. While you can try to remove this mold from your cannabis plant, most experts suggest tossing an infected plant into the bin so it does not threaten other plants in its vicinity. 

What’s The Ideal Humidity for Cannabis Plants?

Humidity is no doubt crucial for your cannabis plant, but it shouldn’t be too high. Too much of anything is bad for cannabis, and humidity is no different. So, you need to ensure your cannabis plant stays cozy without being too sweaty in your grow room.

But before we get into the ideal humidity levels for cannabis plants, it is crucial to know that humidity and temperature go hand in hand, so the following advice will contain instances about temperature management. This is because warm air contains more moisture than cold air, so keeping the grow room cool and managing the temperature goes a long way in managing the humidity levels. 

Here are the ideal relative humidity and temperature ranges for your cannabis plant during each of its growth stages.  

1. Clones 

The seedling or clone stage of your cannabis plant is a sensitive time, but it’s also the stage that requires high humidity levels. So, the best humidity for a seedling or a clone is between 65% to 70%, with temperatures around 77°F during the day and 70°F during the night. 

By giving your cannabis plant high humidity during this time, you are allowing the plant to grow a big, well-established root network that will further help its growth down the line. High humidity also helps the plant to transport water to the leaves, which is crucial at this stage.

If you like cloning your cannabis plants, which is essentially a process of propagating them through cuttings, it’s very important to maintain high humidity levels since clones, like seedlings, also lack a fully developed root system.

Here are a few benefits of high humidity for cloning:

• Moisture: Clones will need lots of moisture in the environment to develop roots. In addition, you should make sure that the growing media never dries out when the clones are planted in them. 
• Less stress: Like seedlings, clones are also very fragile, so you should maintain the perfect environment of high humidity levels of at least 75-85% for good growth. 
• Less water loss: As mentioned before, high humidity during this stage will reduce water loss that occurs through the leaves, helping the plants conserve as much water as possible and reduce stress.

2. Seedling Stage

This is the very initial stage of the plant when the seeds germinate and develop a few leaves. Naturally, the seedlings are very vulnerable at this point and are still establishing their root systems. High humidity, ranging from 60 to 70% will work great for the seedlings and offers various benefits including:

• Moisture for quick and easy germination: Adequate moisture in the growing medium or environment around the seeds ensures that the seeds sprout successfully. Moisture is very important for the seeds to germinate, so high humidity of about 65-70% helps here. If you want the seeds to sprout well and have a high probability of germination, you should make sure that the media doesn’t dry out. This will also ensure that the plants develop strong root systems.
• Reduced water loss: Since seedlings don’t have extensive root systems unlike big plants, they struggle to absorb water. Fast transpiration will affect the seedlings. In this case, high humidity will help the seedlings reduce water loss and allow them to retain moisture. 
• Promotes healthy growth: Since there’s less stress and sufficient moisture, the seedlings will be able to focus only on developing robust root systems. These conditions will also allow the seedlings to grow their true leaves, which is nothing but their first set of leaves. 

3. Vegetative or Growth Stage 

The vegetative stage is where your cannabis plant puts on most of its mass; it grows new branches and well-structured leaves. Here, the humidity levels should be relatively high, at 40% to 70%, but if your leaves look a bit shiny, consider bringing down the humidity further. And stick to temperatures around 71°F to 82°F (22°C to 28°C) during the day and 64°F to 75°F (18°C to 24°C) during the night. 

This is also the period when your cannabis plant establishes its root network to increase the water intake. However, it is suggested that you decrease the humidity gradually when your plant grows since the plant will be absorbing and letting out more water. So, reduce the humidity level by 5% every week. 

Maintaining high humidity at this stage has various benefits, including:

• Growth: High humidity will promote vegetative growth by facilitating increased water absorption through the roots, which in turn helps the plant develop lush foliage and sturdy stems. And, as mentioned earlier, high humidity at this point will also prevent water loss. 
• Resilience: Thanks to all that moisture in the air, the plants become very strong as the environment is stable and protects them from various stressors that can hamper their growth. 
• Prevents growing media from drying: Just like high humidity is beneficial during the germination and seedling stage, it’s great for plants during the early vegetative stage as it prevents the soil from drying faster. This is particularly beneficial if the climate is arid or warm. High humidity will ensure that the roots of the plant access water easily. 

4. Early Flowering Stage 

Once your cannabis plant enters the flowering stage, it already has an established root system, and except for the flowering stretch, it won’t put on any more mass during this stage. However, this is the time it will start sprouting buds, so the humidity must be low to prevent mold and mildew. 

If you had been decreasing the humidity by 5% every week during the vegetative stage, you might already be in the ideal humidity ballpark for the pre-flowering stage, which is between 40% to 50% with temperatures ranging between 68°F to 78°F (20°C to 25°C)

5. Late Flowering Stage

Between the early flowering stage and the late flowering stage (which lasts about 6 to 12 weeks), not much changes except for the maturity of the buds. But since the buds put on more mass, they are even more prone to mold and mildew. So, a lower humidity is ideal in this stage. 

It is recommended that you maintain a low humidity of 30% to 40% during this stage with temperatures ranging between 64°F to 75°F (18°C to 24°C). This will also improve your buds’ taste and overall appearance. 

Do note that whenever you change your grow room’s humidity, it is not a quick change. That can stress out your plant. Instead, you need to be gradual and change humidity by 5% to 10% at a time. 

How to Decrease Humidity for Your Cannabis Plants?

Sure, cannabis needs relatively low humidity during its later stages, but what do you do if you live in a humid region? Fortunately, you are not alone; this is a problem that many growers and farmers face, and they have come up with some excellent and effective solutions for the same. 

Here are the best ways to decrease humidity and, sometimes, deal with it more efficiently for your cannabis plants.

1. Ventilation 

Fresh air is crucial for indoor cannabis plants as it not only keeps the humidity in check but ensures proper photosynthesis and respiration, which are crucial for your cannabis plant’s growth. Plus, your cannabis plants need a lot of carbon dioxide, which can deplete fast if the air is stale and not fresh. 

So, to keep the air fresh and humidity in check, you need to invest in proper ventilation, not just a table fan pointed at your cannabis plant. Here are some of the tips to improve ventilation in your grow room:

• Get an extractor fan that removes or pulls the air out of your grow room, and remember to place it high since warm air rises to the top. For this, measure the CFM of your room and get an appropriate extractor fan; 40 CFM is a good starting point. 
• You also need to strategically place some fans around the grow room to circulate the air within, and the bigger the setup, the more fans you’d need. You need a small oscillating fan for the grow room, and two fans for the exhaust and inlet, and if you want, you can even invest in gardening fans that come with built-in thermostats. 
• If you live in a warm, humid region, it is also a good idea to invest in an air conditioner, especially a mini-split unit. This is expensive, but it works wonders — just pay attention to the conditioner’s BTU. 

Follow these tips and you will significantly reduce the humidity in your grow room. 

2. Pruning and Defoliating 

What if your ventilation is already sorted or if you are growing cannabis outdoors? In that case, consider pruning or defoliating your cannabis plant. This is an excellent training method that makes your plant habitual to a humid environment and it can also boost its yield. 

Essentially, when you prune your cannabis plant of unnecessary leaves and branches, you improve the aeration within the canopy, which works wonders for managing the humidity of the plant. Your plant will breathe a lot better and the high ambient humidity won’t bother it as much. 

Additionally, pruning also encourages your plant to focus its energy on the bud sites instead of sustaining branches that lack any bud sites. This will boost the bud and terpene development processes, leading to a much better, richer yield during the flowering stage. 

3. Dehumidifier 

One of the most effective ways of managing humidity in a grow room is to use a dehumidifier. This system is a lot like an air conditioner — it works by pushing air through a cooling element, which condenses the moisture into a reservoir and lets out “drier” air through the vents. 

These devices even come in portable sizes, floor units, or wheels, so you have a lot of options to pick from. And some units also feature filtration, so they can also help purify the air in your grow room. 

Yes, they are expensive and while they may not make sense for a hobby grower parenting a couple of plants, they are almost an essential addition to the grow room for serious growers. They offer the ultimate control of your grow room’s humidity levels. 

4. Irrigation At the Start of the Light Period 

A subtle aspect that plays a massive role in your cannabis grow room’s humidity levels is the irrigation time. For example, if you water your cannabis plant during the day, a lot of the water may evaporate, increasing the humidity in the grow room. So, what you can do instead is be a bit more conservative with your irrigation. 

You also need to rework the timing of your irrigation. Ideally, you want to irrigate your cannabis plants right before turning on the grow lights for the light period. Doing so reduces the water evaporating into the air due to warm growth lights. 

5. Remove Windbreaks

Chances are, if you are growing cannabis outdoors, your plant is surrounded by many things, whether it is companion plants, a fence, or a windbreak to protect it from various elements in the atmosphere. If humidity is a concern, consider removing these from around the plant to boost the airflow, which will drastically reduce the humidity in the immediate surrounding area of your plant. 

6. Invest in an Automated Climate Control 

Controlling the humidity and temperature may seem like a lot of hassle and rightfully so — it’s hectic. Instead, consider investing in automated climate control that goes a long way in managing the humidity and temperature in your grow room, so you don’t have to worry about those aspects at all. They are a worthy investment for commercial growers. 

7. Pick the Right Cannabis Strains 

You can do everything to keep the humidity in check, but if you try to grow a cannabis strain that’s suited to arid climates in a tropical village, good luck. It will likely not grow well. Instead, you should pick strains that are more suited to your environment even if you choose to grow indoors. 

So, conduct in-depth research on the strains you look at and only pick strains that grow well in high-humidity regions. Some of the best strains for high-humidity regions include Thai, Durban Poison, Jack Herer, Bruce Banner, Super Lemon Haze, and Northern Lights. It’s also wise to choose autoflowering strains so they mature before the weather turns bad. 

8. Use Wet Trimming 

Your battle with high humidity does not end when you harvest the buds, it continues to stay tricky. Once you harvest the buds, you’ll have to trim and dry them in whichever order you like, but it is recommended to use wet trimming for humid regions. 

Dry trimming is where the buds are dried as a whole, with the branches, before getting trimmed so that the moisture within the buds can be drawn out. This is why dry trimming is recommended for cold regions. 

However, if you are growing cannabis in a humid region, it is better to use wet trimming, which involves trimming the buds when they are still moist. Thanks to this, the buds can dry out faster and have lower chances of bud rot or mold. Plus, it makes the trimming process a lot easier and doesn’t waste as much space. 

How to Measure Humidity?

You can only fix this problem when you learn how to measure humidity in your grow room or garden. Eye-balling it or going by the “feel” of it is almost as good as throwing ice on your plants instead of water — may work in theory but the practical aspect is rather useless. 

The best way to do so is using a hygrometer or a humidity meter, which can help you detect the relative humidity in your cannabis grow room easily. In fact, you can even invest in digital hygrometers that can connect to your smartphone and other sensors, allowing you to monitor the humidity at all times and even automate the process of humidity management. 

Summary: Growing Cannabis In Humid Environments: Effects And Stages of Growth

Cannabis may be a sturdy plant, but it’s still sensitive to certain things, one of which is the humidity. If the humidity in your grow room or garden is too high, your cannabis plant can suffer from various problems, including mold, bud rot, nutrient deficiency, stunted growth, and subpar yield. 

This is why it is crucial to maintain the right humidity levels as mentioned earlier. And how do you do that? By using proper ventilation, pruning, and other aerating training techniques, installing a dehumidifier, irrigating at the start of the light period, picking the right cannabis strain, and using wet trimming post-harvest. 

And remember, these techniques only work when you know what you are dealing with. So, consider investing in a hygrometer — the basic ones are cheap but the expensive ones can help automate climate control in your grow room. Depending on your budget and requirements, choose one that suits you the most. 

Humidity can be a pain to deal with for new growers, and you may even lose a plant or two to humidity-induced mold. But this serious problem is quite easy to fix. All that is required on your part is some research, proactive measures, and smart thinking. Do those things and you won’t ever have to deal with high humidity ever again.