Leaves curling after moving from induction light to DE HPS, in very cold temps

My plants seem seriously stressed out, after having them in veg for the past couple of months, waiting for my Flower room to be finished. they were under indagrow brand par 420 lights (12 of them) i just moved them yesterday afternoon to the finished flower room with 1000 watt DE HPS lights (18 of them) which i have set the balests to 60%. there are multiple different strains all seeming to act in the same way. I am worried that when i moved them it was far too cold. It is in the 0 degree F(outside) when i moved them yesterday. They had to be moved from upstairs to downstairs, but had to be brought outside to do so. Could this be a reason as to why the leaves are twisting? The plants are in an ebb and flow set up, feeding every four hours. same for Veg. I was running at around 800-900 PPM using Hydroponic Research Veg& Bloom Nutes. Also using a silica additive and the Plus Life from Hydroponic Research. My PH always ranges from 5.8-6.2. The Temp in the room overnight was right around 60 degrees F. i have turned my AC backhand he temps are rising slowly now. I will update with Pictures shortly.

Silica product is good - it helps build health/strong plants (cells,ect ) sounds like a light and temp issue and when one switches light they need to re-figure your light distance first of all - let temps level out once lighting is correct and them check tetmps

here are some photos of what i am talking about. Some of the pics were taken through my method 7 hps sunglasses lens.

I suspect it is your temps you need a difference in air temp to root zone temps to encourage your plants to drink 10f difference is ideal if your temps were in the 60’s I suspect your res is about the same they should recover as room temp climbs. The cold move certainly didn’t help them too much

What was the day time temps and the relative humidity both day and night? Have you seen the Support Ticket questionnaire?


The temps in the room before i moved them were in the mid 70’s all the time, while running between 27-35% humidity, due to the fact that i had seen some powdery mildew on a few of the plants. After i moved the plants last night, the doors remained open while doing so dropping the temps to around 50 degrees F. The temp never got above 58 degrees last night. i have since risen the heat back up to 75 degrees F. i filled out the support ticket below. thanks.

ILGM Support Ticket:

What is the strain and type Bubbleiyious, sfv-OG, Berry White, Amnesia, Northern Lights, few others.

Indoor or Outdoor? indoor

Size of space- : 29’x13’ 13’6" ceilings. moved from a slightly smaller space with 8 foot ceilings.

Soil or Hydro? Eb and Flow using Hydro Corn.

pH? Reservoir PH between 5.8-6.2

Type and strength of nutrients used? Start with R/O water at 0 PPM. using Hydroponic Research Brand Veg&Bloom base Nutrient (powder). also using the Plus Life additive from HR. also using Armor Si by General Hydroponics.

Temperature? holding steady at 73 degrees F now. last night it did not rise above 59 degrees F. It was -15 degrees F last night.

Humidity %? Day vs. night: was running between 27-40% humidity. those are the average high and lows. (this was in the smaller space) today the humidity has been around 25%: it is extremely cold and dry where i am right now (Maine)

Light system/watts/lumens/FLUX/PAR? now using sun system DE HOODs with Phantom 1000W DE HPS dimmable ballast. currently at 60% power. There are 18 lights set up in the space. Moved from using 12 each Indagrow Par 420 Induction lights.

Ventilation system? Size? CFM? CO2? AC, Humidifier, De-humidifier? the 18 HPS Hoods are being vented with 1 12 inch Max-Fan pulling air from the outside, running into 3 rows of 6 lights. each row has 8 inch max-fans at the end of the rows feeding into the exhaust system. Also bringing in cold air from the outside to cool room when needed. I have 3, 70 pint dehumidifiers set up.

Number “weeks/days” from into Season, Vegetative Growth or Bloom/flowering? most of the plants have been in the smaller veg room for a couple of months. they are averaging around 3-6 feet tall right now. Just moved into the Bigger space yesterday while it was around -5 degrees F. the plants looked fine before they were moved. They had to be moved going outside to do so. when they got to their new room, it was about 2-5 minutes before i noticed them drooping and the leaves turning up.

Ouch that’s some damn cold weather to move your poor ladies in what is you res temp like? you may have some frost bite it doesn’t take long in negative temps with thin little leaves

ilovegrowingMay '13 1

THC will not be affected by the frost. But, plant tissue can incur some damage. Temperatures that dip below 48.2F (9C) usually affect the marijuana plant in some way. Leaves will suffer damage and need to repair themselves prior to resuming growth or ripening—a process that could take a few days of good weather to complete. If cold weather persists for several days, the damage to the plant is multiplied because it is weakened and increasingly less capable of repairing itself.

To return the marijuana plant to normalcy, the temperature needs to rise into the 60’s, and the plants need to get adequate sunlight to power photosynthesis. When temperatures dip even further down to 40F (4C), leaves, flowers, and other plant parts suffer even more. It takes a couple of days for a plant to fully recover from the damage, and it’s not likely because of the generally cloudy conditions associated with fall. The energy (sunlight) available is limited and the maturation of the bud and THC production is curtailed. Stopping the production of THC helps the plant save energy, particularly when it’s not needed to protect from insects and UV light. Under these conditions, the THC that the marijuana plant already produced is not eradicated by the frost, but you won’t find any new production. Unless there is a genuine possibility of warm, sunny weather in the forecast, you’ll probably want to harvest the marijuana plants.


This is a quote from robert concerning low temperatures

thanks for the info. my res temp is at 66 degrees F, and the room is at 75 degrees F. i have a space to keep the res in a different room from the lights, so hoping i can keep those temps. unfortunately the ladies are still looking in rough shape, some of them anyway. the curled up leaves have started to dry out and become crispy…some worse than others.

You probably set yourself back 4-7 days, but they’ll return, I had to do an emergency move including a 45 min drive back in 2000, up here in Nova Scotia, -12 F. Same basic situation as far as shock to the ladies, but once back in the regulated environment a few days and voila a lovely harvest in the end. Probably increase THC level for you.


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Update. all my ladies came back very nicely. It took about a week to 10 days to really notice good improvement. I ended up keeping them in veg for around 14 days before i switched the lights over to 12/12. I was already seeing nice new growth in those two weeks. There are definitely still a good amount of yellow dead looking leaves, some of which stems are still very plump and alive. Flower formation doesn’t seem to be affected at all. Day 22 and some nice looking flowers already. I will update with some pics tomorrow.



That’s good to hear. It is what I thought you would have happen. Enjoy the rest of the show.



Very nice looking bud! Mike

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Always love bud porn :stuck_out_tongue: