Humidity is an often-overlooked part of keeping your cannabis grow healthy. Because there’s a wider range of safe humidity levels, most growers focus on other aspects of the grow and let humidity sort itself out. However, humidity can act Humidity is an often-overlooked part of keeping your cannabis grow healthy. Because there’s a wider range of safe humidity levels, most growers focus on other aspects of the grow and let humidity sort itself out. However, humidity can actually affect the outcome of your grow quite a bit. If you’re confused about how to handle humidity, here are the basics.
How Does Humidity Affect Cannabis?
Humidity is the amount of water vapor in the air. The right humidity level is important for your plants, because too much or too little affects how cannabis “breathes.” If you get the balance wrong, your plant can start to show strange symptoms.
Plants take in ually affect the outcome of your grow quite a bit. If you’re confused about how to handle humidity, here are the basics.
How Does Humidity Affect Cannabis?
Humidity is the amount of water vapor in the air. The right humidity level is important for your plants, because too much or too little affects how cannabis “breathes.” If you get the balance wrong, your plant can start to show strange symptoms.
Plants take in air through little pores in their leaves. They also expel air (well, technically CO2) and excess water through those same pores. The problem is that when the air is too dry, your cannabis will lose water much more quickly than normal. On the other hand, when there is too much humidity in the air, it’s harder for your plant to get rid of excess water. That can lead to problems with pests, mildew, and rot.
Every growth stage requires slightly different ideal humidity ranges. You’re essentially recreating cannabis’ natural habitat when you do this, which helps it grow better. Over the course of a summer, humidity changes, so cannabis plants evolved to take that into account.
Over the course of the grow, you want to slowly taper the amount of humidity down. Seedlings need the most humidity, with every stage thereafter needing less. This is because seedlings and clones don’t have well-established root systems. By keeping the humidity up, you can avoid moisture leaving through their leaves that they can’t afford to lose. On average, keeping your humidity at 70% is ideal for very young plants.
Once your baby plants have transitioned into the vegetation phase, you can start lowering humidity. Do the transition slowly. Ideally, lower humidity about 5% a week, so your plants have time to adjust.
The vegetative phase is where you have the most leeway in what your plants will tolerate. Anywhere from 40% to 70% humidity is tolerated by plants in the vegetative stage. Keeping your humidity levels towards the middle of that range, from about 50% to 55%, is best. That way your plants aren’t at risk of pests or drying out.
Once your plants are in the flowering stage, you need to tighten up your humidity levels. Blooming cannabis plants tolerate 40% to 50% humidity best. Many growers even advocate dropping humidity levels to below 40% for the final week or two before harvest. This is a trick to stress your plants just right, so they create more of the trichomes you want.
How to Troubleshoot Cannabis Humidity Problems
These general ranges regarding what your marijuana plants should be able to tolerate humidity aren’t foolproof. Sometimes your plants will need humidity higher or lower, depending on things like pests, temperature, and their strain. Being able to tell when your plants are struggling will help you keep your plants healthier.
Signs of Low Humidity in Cannabis
If your humidity isn’t high enough, your plants will be drying out very quickly. If you’re watering constantly, your humidity may not be high enough. In extreme cases, this can include signs like your plants’ leaves starting to turn brown and dry out.
Low humidity can also lead to your plants showing signs of nutrient burn. Since your plants are losing so much water through their leaves, they’re absorbing a lot more through their roots. That comes with absorbing more nutrients from their growth medium, possibly to the point of nute burn (aka nutrient burn). If you’re seeing signs of burn in your plants, check your humidity along with your fertilization schedule.
Finally, spider mites love the conditions created by low humidity. If you have a mite infestation that just keeps coming back, try raising the humidity as soon as possible.
Signs of High Humidity in Cannabis
If your humidity is too high, you face an entirely different set of problems. First and foremost, mold, fungus, mildew, and other nasty problems love damp conditions. They also love the nooks and crannies found in a densely-packed grow room. High humidity can lead to mold on your walls, your plants, and worst of all, your bud. If your bud has mold on it, it’s not safe to consume, and your harvest goes to waste. These problems can also trigger asthma or allergy attacks on your end.
How to Adjust Humidity
Humidity is easy to adjust. There are plenty of tools on the market that can help you raise or lower your humidity until it’s just right. You just need to choose the style that works best for you.
The first and most important step is to get a hygrometer. This is a device that measures the ambient humidity in your grow. Without one, it’s hard to tell whether your fix is actually doing anything for your plants.
How to Raise Humidity
Low humidity is most often a problem faced by new growers. Ironically, that’s because everyone warns of the dangers of high humidity. Many new growers overcompensate in the other directions, and dry out their grow to the point where their plants are struggling. If that’s the case, then the fix for low humidity is easy – stop running the dehumidifiers so often.
If your problem isn’t self-caused, then there are other options. There’s a humidifier on the market for every size of space. Whether your grow tent is five square feet or fifty, you can get humidifiers that should work for you.
You can also go low tech. Get a wide-mouthed bucket or a paint tray and fill it with water. Place it under the grow light, in the middle of your plants. The light should evaporate the water over time, raising the ambient humidity. The one downside here is that you can’t control how quickly this happens, so you might end up going too far in the other direction. Check your hygrometer to see whether it’s working too well.
How to Lower Humidity
Lowering humidity is harder than raising it. Most grows will deal with high humidity at one point or another Your plants are expelling water through their leaves, and some water evaporates from the soil, after all. There are a couple techniques to lower humidity, but they require patience.
The first and most obvious method is to get and use a dehumidifier. Many dehumidifiers allow you to select the humidity range you want. This guarantees you’ll keep your grow in the right place. Just make sure you have enough room to fit the dehumidifier you want into your grow!
You can also run your ventilation system harder. This works by blowing out stale, humid air, and pulling in cool, dry air from outside. This usually works. However, if your external environment is also too humid, this can backfire by pulling in wet air.
Finally, you can get humidity packs. These packs absorb water from the air whenever there’s more than a certain humidity level. They’re a great solution for long-term humidity maintenance, because they help keep things stable. They also are useful for drying and curing cannabis, by absorbing the humidity the plants give off.
Humidity shouldn’t be overlooked when it comes to cannabis growing. The right humidity level at the right time can help take your harvest from okay to awesome. Keep an eye on your humidity, and don’t be afraid to adjust it if you see problems. Your plants will thank you for it.