What happens when humidity is too high?

Discussion in 'Growing Marijuana Indoors' started by untamedlion33, May 5, 2011.

  1. my humidity stays pretty high most of the time. anywhare between 80 to 90% when the lights shut off to 40 - 75% when the lights are on.
  2. What kind of set-up and lighting are you running first off that it drops your humidity in half? What is your medium, what is your air flow system. Lots of variables will affect this but to drop in half is a huge drop in humidity!?!?!?????!!
    No worries you have not done anything wrong. It will just take more info to help you out;)
  3. right now they are under a 150 watt hps and a couple halogen work lights. i use miracle grow and flora grow stuff.
  4. My two cents- For some reason your humidity is high as fuck. Firstly, make sure that your hygrometer is working properly. A lot of the cheaper ones don't show accurate readings. Secondly, make sure you have a fan running in the grow area. Lastly, if you suspect that your humidity really is that high, you can confirm this by putting a glass cup in the room, if the RH reaches its due point, you should see condensation on the glass.

    If it is that high, place a container of damp rid in the grow area and it should bring down the RH a few notches.

  5. Mold is very likely to set in with high RH levels. Massive amounts of info is needed before anyone can suggest how to approach the problem. Good luck.
  6. see thats the thing i have alot of fans and stuff going and havnt noticed any mold or anything. I think all this humidity is just coming from the air. buffalo gets really humid this time of year plus the heater is off so. idk i guess a better question is does high humidity make the buds smaller?
  7. as far as i know high humidty wont effect ur grow directly (could be wrong it might effect how the plant is able to breath) what it will do tho for sure is put ur chances of mold up by alot, my dehum broke on me recently day 63 into flower and it forced me to chop early as there was moldy buds and i lost maybe 15grams of green. either way it aint a good thing. more so if ur in late flowering.

  8. How high was your humidity that mold developed? I'm curious because I also have high humidity (currently 70%) but I'm 7 weeks into flowering... Just recently put a dehumidifier in there, but it's an old one and I am not sure if it still works efficiently so I am checking in a bit when lights come on.
  9. #9 sauce78, May 5, 2011
    Last edited by a moderator: May 5, 2011
    What happens at 90% humidity:
    The driving force of water moving from root hairs up the plant and out the stomata is derived from a pressure gradient. Water diffuses from areas of high concentration to areas of low concentration.

    Water potential=Sugar concentration + pressure + gravity.

    Therefore, if the humidity of the area outside of the plant is at 90%, a weak pressure gradient is created because there is little difference in concentration from the plant and the atmosphere.
    Resulting in a significant decrease of your plant’s evapotranspiration rate (ET).

    Evapotranspiration is water loss due to both evaporation of water on the plant/soil surface as well as water loss due to water transpiring out of the leaf stomata. As evapotranspiration takes place, the humidity immediately surrounding the leaves will become saturated with water vapor.

    The end result is water not being drawn up from the root zone and neither any of the nutrients. Developing fruits will not receive any of the food from the soil they need to be healthy. This is why high humidity will cause blossom rot in many veggies.

    Additional information:
    •\tHigh Humidity leads to many plant pathogens.
    •\tKeep fans oscillating and air moving to reduce humidity.
    •\tIncrease solar radiation (light) as well as temperature to increase ET.
    •\tIf temp is too high and humidity is too low, ET increases, which can cause too much water/nutrient uptake leading tip burn.
    • Keep humidity at 40-60%
    • Keep higher when the plant is not actively fruiting/reproducing.
  10. im not sure what it got up to cause my dehum had a built in hygro display, but it was very high the walls were saturated.
  11. Make sure you breath through your nose and not your mouth when you are in the room as to not add to the RH. :D

    Sorry.... couldn't resist.

  12. Ah, gotcha... Mine's down to 60%, the dehumidifier pulled out an entire bucketful of water. Really hoping not to run into that issue... no more muggy days out! >.<

    sauce78 thanks for the info... good to know!
  13. Anytime brudda, I can talk hours and hours on plants.
    One love.
  14. I'm pretty sure halogens are a waste to grow with. Are you misting your plants or the box? Do you water every day or two days?
  15. Had the same pro lem along time ago. Capacitor on dehumidifier went out on me.. spiked upwards of 80% rh.. waited for a new part so in the mean time i went and dropped about 80$ in damp rid. Dropped me back to around 55%.. from my experience the only issues that arise are how it breathes and drinks water. showed signs of classic over watering because it couldnt drink the normal amounts of water as it would in normal rh conditions. Hope this helps.
  16. Missed Missed the dates big time hahahaha...

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