Ideal Temperature and Humidity for Grow Tents
When it comes to growing marijuana, I think a lot of new growers are mostly concerned with the soil and the required lighting. More-so, probably the lighting. If you really are interested in maximizing the amount of buds you get to harvest, then learning about temperatures and humidity requirements for growing marijuana is important.
So, what is the ideal temperature and humidity for growing marijuana in a grow tent? The ideal temperature for the vegetative (growth) stage is between 20 Celsius and 30 Celsius (68F to 86F). The ideal temperature for the flowering (budding) stage is 20 to 25 Celsius (68F to 77F). The ideal humidity is anywhere between 40% to 60% humidity.
What is the Best Temperature for Vegetative Stage in a Grow Tent?
Trying to replicate what the temperature would be outside in your weed plant’s native home during growing season is how you will have success with your weed plants. During the daytime in the veg stage, you want to mimic hot summer days. If you can get your grow tent up to 30 Celsius (86 Fahrenheit), it’s going to grow like a weed.
At nighttime, let the tent cool down to the lower 20’s (68 to 75 Fahrenheit), if possible. The cooler temperature mimics what happens in nature and as a bonus, the cooler temperature helps to promote plant growth, just as much as the very hot daytime temps.
I have an article on ways to heat your grow tent that I think you will find helpful when you want to figure out different options for heating your grow tent. Please check it out when you are finished with this article. It can be found here.
What Temperature Should my Grow Tent be During Flowering?
When it’s time to flip the lighting schedule and encourage the marijuana’s flowers/buds to start growing, you are now trying to mimic fall weather. This means, lower the temperature in the grow tent and possibly offering a different light.
You could keep the temp as high as it has been, but it won’t speed up the process for you.
My recommendation is when you flip your lighting to 12/12 timing, lower the tents temperature by up to 5 Celsius (down to 77 Fahrenheit). This will get your weed plants to not only take note of the amount of lighting being received, but the lower temperature will get attention as well.
- During the daytime, keep the tents temp in the range of 20 to 25 Celsius (68 to 77 Fahrenheit), you could go as low as 18 Celsius. By keeping the temperature lower (less than 28C/82F) during the flowering stage, the trichomes on the plant will be more potent than if you left the grow tent at the same temp as it was in the veg stage.
- Lower the temperature at night by a few degrees, similar to what you were doing in the veg stage.
- As an added bonus, when you think you are two weeks or less from cutting down the plants, increase the temperature difference between night and day even more. I would just lower the nighttime temp, not the daytime. By doing this, your buds will grow bigger and more dense. It signals to the plants that the growing time is almost over so it better produce those big buds ASAP!
What Should My Grow Tent Humidity be for Marijuana?
As stated earlier, the grow tents humidity should be somewhere in the range of 40% to 60%.
There are a couple of things to take note of, if you want to increase your chance of success.
- It is preferred your pot plants are grown in higher humidity while in the veg stage and lower humidity in the budding stage.
- For the flowering or budding growing stage, it is important to decrease the humidity more and more as you get closer to harvesting. This mimics what happens outside in the fall season.
What Happens if Humidity is too Low in Grow Room?
It is possible to not have enough humidity in your grow tent/room during the vegetative stage. The cons to this happening include your plants growth being stunted. The stomata on your plants could potentially close-up which means they aren’t getting the oxygen exchange they need to be getting. Your plants might not die, but their growth will indeed be affected.
This is, of course, an extreme case of lower humidity. If you live in a region where it is very dry, then you should be aware of this condition.
It is okay to have lower humidity close to the 40% level during the flowering stage. 40% is not dangerously low, but low enough to benefit your plants.
How Do You Keep Humidity High in a Grow Tent?
Keep humidity in a grow tent involves two aspects. Providing a source of humidity and keeping the humidity in the tent for as long as possible. Let’s look at both.
- Creating humidity in a grow tent shouldn’t be that hard, one would think. I have a cool mist humidifier with a humidity setting so it shuts off when the desired level of humidity is reached. It’s like THIS ONE over on Amazon.
- Another way I have used in the past is to fill up a 5-gallon pail with water and insert an aquarium heater into the water. You not only get the benefit of the water and humidity, but a nice way to help heat a smaller tent. I have an article with some great ideas on heating grow tents. Make sure to check it out when you are done here. How to heat a grow tent.
- Keeping a tent humid is all about sealing up any areas of the tent that will allow air out of or into the tent. Using tuck tape or tape of your choice, if you taped over all of the stitching on the inside of the tent, it would help in stopping the tent from losing humidity so quickly.
Why is There Condensation in My Grow Tent?
If you let the humidity level get to high, you run the risk of condensation building up in the tent. You could also end up with mold which you don’t want.
You can invest in a hygrometer like this one (measures moisture/humidity in the air) or do as I previously suggested, use a humidifier and get one that shuts off when the air in the tent reaches the set humidity level.
Do You Need Ventilation in a Grow Tent?
No, you can grow marijuana without ventilation. I have done it.
You will benefit, though, if you do have an inline ventilation kit. Especially, when it comes to controlling heat and humidity. An inline ventilation kit will help you move the air in and out as needed.
This grow tent ventilation kit on Amazon will get you started.
Related Questions
How Do I Keep My Grow Room Warm When the Lights are Off?
When the lights are off, you want the temperature to drop down a bit, yet you still need to keep it warm, especially in the vegetative stage. A way to do this is have a heater which has a thermostat incorporated. If you are looking for other ideas, I put a link higher up on this page to an article I have about heating grow tents. Make sure to check it out.
How Can I Keep My Grow Tent Cool in the Summer?
This is one of those problems that would have to be solved case by case as every situation is different. Since you are using a grow tent, the benefit you have over a grow room is you are portable. Move the tent to the coolest part of your home.
Another option is to move the tent, so air conditioning is blowing nearby.
Yet another option is to have a fan inside the tent and leave the zipper open during the lights on time of the day. Just be careful not to let the plants get to cool.
I hope you were able to find something useful in this article for your particular growing situation.
Please feel free to check out other helpful articles on my site and if you have a moment, please share this article on Pinterest or any other social media site.
Thank you and good luck.
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