What Are The Best Temperature & Humidity Levels For Growing Marijuana?

Marshydro

Marshydro sales rep
AFN Authorized Vendor
Joined
Jan 12, 2015
Messages
8,384
Reputation
1,030
Reaction score
18,987
Points
0
Age
33
Website
www.mars-hydro.com
Some cannabis strains could survive in suboptimal environments, but they probably won’t thrive. If you want to grow fire indoor flowers, you have to take control of your climate. It’s crucial to monitor the relationship between temperature and humidity as your cannabis plant matures.

From CO2 levels to watering schedules, temp and humidity impact many aspects of your grow operations. Since warm air retains moisture, it can supply crucial hydration to fragile seedlings. However, as plants mature, too much humidity could pose an increased risk of mold.
Average Temperature & Humidity Levels For Cannabis Plants
Finding the optimal temperature may take a bit of tinkering, but there are a few general heat and humidity levels that cultivators could use as a guide.

1000x300-2.jpg


Keep It Steamy For Seedlings
Since cannabis seedlings don’t have a sturdy root structure, they will absorb most of their water through the air. For this reason, cultivators need to ramp up their average humidity during this initial stage of growth.

Most seedlings perform well in an environment with 65 - 75% humidity and temperatures between 68° - 78° F. However, if you’re working with clones rather than seedlings, you should invest in a humidity dome. Young clones need the highest humidity rates of about 75 - 90% for optimal growth.

While seedlings need high humidity rates, cultivators still have to watch out for complications like mold. It’s best to start with the highest humidity rate and gradually decrease as plants approach vegetation.

Also, home-growers that live in a state with cold temperatures should invest in a high-quality Mars Hydro heat mat. These devices help keep your delicate seedlings warm as they begin developing their roots.
Increase Ventilation For The Vegetative Stage
When cannabis plants transition to the vegetative stage, they don’t need as much water from the atmosphere. In fact, cultivators should begin encouraging their strains to develop a robust root system by watering on the soil around their plants.

To assist this natural transition, it’s best to dial back humidity to the 60 - 45% range. However, you should consider increasing the ambient temperature to mimic the summer season. An optimal temperature range for vegetation is between 70° - 82° F.

High heat is especially significant if you’re adding CO2 to your grow space. Plants need higher average temperatures to use supplemental CO2 for photosynthesis. Depending on how much CO2 you add to your grow space, you could safely raise temps to 85° - 90° F.

Please don’t forget to incorporate a ventilation fan into your cultivation strategy. These fans help strengthen stems and reduce the risk of pests and mildew.
Dehumidify For The Dankest Buds — Temperatures During Flowering
As strains move into the flowering stage, they should have a fully-developed root system. Therefore, these plants don’t need high humidity for their hydration needs.

In fact, excessive heat will significantly increase the risk of mold and hermaphroditism. If you have a dehumidifier and inline fan, this is the best time to put them to use.

Ideal humidity ranges for flowering plants are about 50 - 30%. Temperatures should decrease throughout flowering to mimic the change from summer to autumn, with average temps between 70° - 80° F.
Heat & Humidity For Cannabis — A Few Final Considerations
TSW2000_1_.jpg



Most cannabis plants perform best in a climate that resembles subtropical regions. Also, every strain needs the highest amount of humidity in the seedling phase, since the plant’s roots are at their weakest during this stage. As the cannabis plant matures, cultivators should keep reducing their room’s total humidity to avoid complications like mildew.

While these temp and humidity guidelines work for most cannabis plants, cultivators must double-check strain-specific guidance. For instance, full-bred sativa strains perform better in areas that mimic regions like Thailand or South America. By contrast, indicas could fare well in grow rooms with slightly lower temperature and humidity levels.

Balancing heat and humidity may not come easily, and the ratios that work for one hybrid may not work for another. Be sure to take detailed notes of average temps and humidity levels to better understand the ideal setting for each strain.

Universal Temperature and Humidity Levels For Indoor Cannabis Growing

Growth stageTemperatureHumidity
Seeding68° - 78° F75-65%
Vegetation70° - 82° F60-45%
Flowering70° - 80° F50-30%

For better preservation:

e_and_humidity_levels_for_cannabis-mars_hydro_1__1.jpg

If you have a different opinion, say it and let's discuss it.
 
A different opinion?, No, but where I live is a high humidity area and I still haven't gotten a dehumidifier...no room for one......I just defoliate like crazy and run open front with lots of air movement from fans and the exhaust on high and A/C when the temps go up.....was 65% this morning (damn autopots).....usually will drop to 40-50% range after a bit....... So far have had no problems with bud rot or mold.... A new tent is in the works but sorry to say it won't be one of the MH tents, or a off the shelf.....odd size space so gotta build my own....34 inch x 52 inch
 
I want a grow tent with insulated walls, maybe take note of hoop houses with an inflatable two layer plastic sheeting that gets inflated only when extra insulation is needed. Would love the option of a winter basement tent. Maybe like a blanket woven into the tent liner itself? Maybe an add-on liner that slides over the standard tent? I would put up with limited access and decreased durability for increased insulation. Whether or not it would amount to an appreciable increase in temp is yet to be tested as other factors like heat loss to ventilation will come into play but worth looking into none the less. Another thing would be zippers with pulls on the inside too, I find myself walking into my bigger tent and desiring to close the door(but I can’t) as outside the tent is 55 and inside is 70’s by the time I’m done temps in tent can drop to mid 60’s, but not if I could close the door….(don’t own a mars tent so not sure if this is even applicable)
 
A different opinion?, No, but where I live is a high humidity area and I still haven't gotten a dehumidifier...no room for one......I just defoliate like crazy and run open front with lots of air movement from fans and the exhaust on high and A/C when the temps go up.....was 65% this morning (damn autopots).....usually will drop to 40-50% range after a bit....... So far have had no problems with bud rot or mold.... A new tent is in the works but sorry to say it won't be one of the MH tents, or a off the shelf.....odd size space so gotta build my own....34 inch x 52 inch
Mine is the opposite. Low humidity, no worries about mold. Although faster-growing plants definitely can't be in a small pot, I've found that if I have a large pot, I don't have to worry about it. I do cover weak seedlings or actually usually just have the light a little higher than normal until the plants are a week or so old. I think growing in a place like Florida or the tropics would be very difficult.
 
Mine is the opposite. Low humidity, no worries about mold. Although faster-growing plants definitely can't be in a small pot, I've found that if I have a large pot, I don't have to worry about it. I do cover weak seedlings or actually usually just have the light a little higher than normal until the plants are a week or so old. I think growing in a place like Florida or the tropics would be very difficult.
What would you say is having the lights a little higher than normal? I always stuff light down my plants throats from the start. My big grow I have the light 24 inches above which is higher than I would usually have them.
 
I usually grow in the 80s (as high as 88 summer time) with humidity in the 60s. Haven’t had issues with plants and all dense buds and no mold so far as a matter of fact since I started growing many years ago I’ve never had that issue of mold.
But many people have different results so whatever works for your space keep doing it :headbang: :jointman:
 
I usually grow in the 80s (as high as 88 summer time) with humidity in the 60s. Haven’t had issues with plants and all dense buds and no mold so far as a matter of fact since I started growing many years ago I’ve never had that issue of mold.
But many people have different results so whatever works for your space keep doing it :headbang: :jointman:
My humidity stays between 30-40 and temps 70-85 depending on lights on/off. No issues yet.
 
Only downside of my temp swings is EVERYTHING turns purple. Don’t get me wrong purple bud is pretty bud I want some green.
 
What would you say is having the lights a little higher than normal? I always stuff light down my plants throats from the start. My big grow I have the light 24 inches above which is higher than I would usually have them.
I've burned seedlings. So I'm easy on them for the first couple of weeks. But after that I get the light as close as possible. I don't have a meter, but I've learned that the leaves will tell you when the light is absolutely perfect.

But maybe 18 inches is higher than normal? It depends on the light too. I have a cob light that I can't get much closer than 24". But I have some cheaper lights that can get closer than 10" and my SP-3000 that stays around 14-15" I guess.
 
I've burned seedlings. So I'm easy on them for the first couple of weeks. But after that I get the light as close as possible. I don't have a meter, but I've learned that the leaves will tell you when the light is absolutely perfect.

But maybe 18 inches is higher than normal? It depends on the light too. I have a cob light that I can't get much closer than 24". But I have some cheaper lights that can get closer than 10" and my SP-3000 that stays around 14-15" I guess.
I have my sf2000 about 22 inches above my seedlings. It’s a new light so I’m not sure where to have it yet. I want a little stretch out of my seedlings just to keep the bottom leaves out of the soil but not to much.
 
Back
Top