HEAT STRESS, but its not hot...

[teddy d]

I have a few young clones 2 weeks old under a 600w hps about 15 inch from the canopy the termometer is saying 84-88F at the top of the center plant right under the bulb. i have a large fan blowing down on the light/plants. my exhaust runs for 15 min every hour with a passive intake because the outside air is still about 58F i also have a heater on low. I have had experience with cold stress due to cold drafts when the fan was running 24/7 thats why it only runs 15 min every hour.

all the new edges of the large fan leaves are curling up (alligator tooth style) classic heat stress but its not even WARM on my hand at the canopy level never mind hot.

is it cuz they are young? will they grow out of it?

other causes?

ph is good, FFOF soil, everything is in order...

 

[Dr.Dank]

at that young you should have them pretty far from the HID. I had mine four feet away and to the side now I always run a small 4 tube 2' T5 over my clones so I can have it directly overhead so they dont lean like crazy. but yeah your burnin em up I think any pics?

 

[Dr.Dank]

I also keep my room max 80 and as low as 55 as long as day/night isnt more than about 10 degrees difference. also your humidity for clones should be close to 100% if not in some sort of aeroponic cloning machine

 

[Roddy]

Sounds hot to me, why using a heater if it's already 80+ in there?

 

[MosesPMG]

young plants cant handle and HID. until they are about 4 weeks cfls or T5s or anything like that will work. If you are going to use the HID keep it about 2' away

 

[The Hemp Goddess]

Temps of 88 are too high--it is simply too warm in your space. You need to run your exhaust more than 15 min every hour. Air that is 58 is not too cool for your plants. I bring air that is far cooler into my space and have never had "cold stress"

 

[teddy d]

thg i had big problems this winter with sunted plants from bringing in cold air. even though my thermometer said 72 the cold drafts created by drawing cold air in was affecting leaf temp big itme but the termometer did not register those cold air currents. as soon as i put in a heater and ran exausted on a timer the came back to life. so yes i am not going to draw 58 F air in to the space constantly.

if i turn the heater off the thermometer will be in the 70s under the light but the surrounding cooler air always screws my plnats up in the past. in my experience the radiant heat from the light is not enough

it seems the room needs its own stable temp, and then I factor in the light to get my canopy temp. mostly 84f

 

[woodydude]

My friend had a problem with bringing in cold air to his room. The answer wasnt to add a heater, it was to direct the cold air at the light. This cooled the light and prevented a "micro climate" for the plants.
Difficult to advies without pics but I would suggest looking into wome way of directing your intake air at the light or at least away from the plants, perhaps the top of the room since thats where warm air goes.

Peace.W

 

[The Hemp Goddess]

Well, I can tell you that temps of 58 are not too cold for mj.

 

[StoneyBud]

I have a few young clones 2 weeks old under a 600w hps about 15 inch from the canopy the thermometer is saying 84-88F at the top of the center plant right under the bulb. i have a large fan blowing down on the light/plants. my exhaust runs for 15 min every hour with a passive intake because the outside air is still about 58F i also have a heater on low. I have had experience with cold stress due to cold drafts when the fan was running 24/7 that's why it only runs 15 min every hour.

all the new edges of the large fan leaves are curling up (alligator tooth style) classic heat stress but its not even WARM on my hand at the canopy level never mind hot.

is it cuz they are young? will they grow out of it?

other causes?

ph is good, FFOF soil, everything is in order...

HID lights put out IR light. IR light will burn plants if too much hits them. No amount of wind will do anything to IR light.

Keeping the proper distance from lamps with IR light is the only way to prevent burning by the IR light.

The "Back-of-the-hand" test isn't accurate. Many people have tolerance to heat that others don't. Use one of those new-fangled gadgets called a thermometer at canopy level to find your heat issues.

Slowly bring the light closer while watching both the thermometer and your plants for reactions to the closer positioning.

 

[Roddy]

Sounds like a lot of work to tell if it's hot, I'll stick to the tried and true back of hand!

Teddy, imho, it's too hot in that room!

 

[teddy d]

new fangled? are you being condescending? I already said I had a thermometer at the canopy. its 84F

you guys are saying thats too warm although i have had plants in the upper 90's with much less signs of stress. maybe the IR is a big part like you stated.

ill just raise the light even though it doesn't seem like i should have to. i have seen people use 4 foot parabolic reflectors dropped right on the canopy with 1000w, hot as heck at the canopy level, plants thriving!

here is a chart i found that states 8 inches is the closest you can put a 600w hps based on light (ir?) not heat.

 

[Roddy]

I don't think the thermometer comment was aimed at you lol, I'd consider Stoney a good person, don't take his comment as slanted at you in any way.

I can only tell you what my thought is and I know most in here (if not all) keep heat DOWN, not try to raise it with heaters...I know my temps were constantly at 60's during day and low 50's at night all winter, great yields and smoke! I can't recall the temps THC starts breaking down.....

 

[teddy d]

I know most in here (if not all) keep heat DOWN, not try to raise it with heaters..

. yeh most of the time. but not in a basement in harsh winter.

I can't recall the temps THC starts breaking down.....

i have mel frank's "marijuana groweres guid" and he goes in depth on this subject but says in simple terms: potency drops significantly when below 60F and above 90F.

The best test group with highest THC production he mentions in the book is 75F daytime / 75F nightime.

 

[StoneyBud]

new fangled? are you being condescending? I already said I had a thermometer at the canopy. its 84F

you guys are saying thats too warm although i have had plants in the upper 90's with much less signs of stress. maybe the IR is a big part like you stated.

ill just raise the light even though it doesn't seem like i should have to. i have seen people use 4 foot parabolic reflectors dropped right on the canopy with 1000w, hot as heck at the canopy level, plants thriving!

here is a chart i found that states 8 inches is the closest you can put a 600w hps based on light (ir?) not heat.

No, I wasn't being an a-hole man. I was trying to be funny. I don't know how close your plants are to the bulb or how much IR your specific bulb puts out, but IR can be a factor with burn. Its a big reason we acclimate plants when moving them outside in the spring. The IR from the sun is a radical change from their low IR seedling home.

84 is warm. The temperature of the root zone plays an important part in the temperature equation. Lower the root-zone temp by 5 degrees and the plants will tolerate 5 degrees warmer above the root zone. This doesn't go for extremes, but between 70 and 90F, the temps can be played a little by altering the root zone temps. The same holds true the other way around also. Put a heat mat beneath a container plant and it will tolerate a cool basement without a flinch.

If your root-zone is also 80+ and the plant above the root-zone is at 84F, then that could well be your problem. The plants entire chemistry will alter in an attempt to survive the temps. It will probably not absorb some of the required nutes and even water exchange will differ from a healthy, happy plant at 74-76F.

Man, I'd have to be standing in front of your plants to tell what is really happening, but it could be any or all of the suggested problems. IR, Heat, Root Temps, Light Distance...only time will tell after you've found the culprit(s).

The age and size of the clones are part of the issue also. Water movement in plants that size (2 weeks old), is much less than in a mature plant. If heat goes in 1/100th of an inch at "X" distance from the bulb, then when the stem is much, much smaller, the proportion of the stem that is heated will be radically increased and may be a large part of the problem.

Like I said, I can't really tell without some good pics and even better, if I was standing there looking at them.

Hey, my thermometer comment was a poke at all the gadgets there are now also. Holy hell man, they have gadgets for everything from mixing and delivering nutes to imitating the suns movement. A good old fashioned, plain old mercury thermometer has been working for a long, long time. I love simple when simple works well. They don't need calibrating and they never stop doing it right until you actually break them.

 

[Roddy]

. yeh most of the time. but not in a basement in harsh winter.



i have mel frank's "marijuana groweres guid" and he goes in depth on this subject but says in simple terms: potency drops significantly when below 60F and above 90F.

The best test group with highest THC production he mentions in the book is 75F daytime / 75F nightime.

I grow in an unheated pantry which is very drafty, I know what you're saying! I did heat my room all winter...but as I said, my temps dictated that I needed to!

Good post Stoney! You must spread some Reputation around before giving it to StoneyBud again.

 

[teddy d]

great post Stoney! that could be very helpful. the weather is starting to warm up so im learning how to deal with blistering cold, transitioning into spring/summer.

1st step: raised the light. see what happens. the plants are nicely rooted and have taken to the new soil/ pots nicely in the past 2 weeks. really flourishing in the past week so they are not really babies anymore, and loving the Ocean forest.

 

[teddy d]

young plants cant handle and HID. until they are about 4 weeks cfls or T5s or anything like that will work. If you are going to use the HID keep it about 2' away

dude. 4 weeks could be a big plant under good light. you DONT have to wait that long to give them HID lighting. no way.

 

[bho_expertz]

I give HID light since germination ... But that is all i have, no CFL for me.

 

[teddy d]

If your root-zone is also 80+ and the plant above the root-zone is at 84F, then that could well be your problem. The plants entire chemistry will alter in an attempt to survive the temps.

well they are on concrete so i would think its slightly cooler at the floor level obviously but i dont know about 5 degrees... it seems that the soil when moist is pretty cool when i push my finger into the soil.

anyway, i dont forsee a huge problem they are getting big fast and i did move the light up a good bit higher. but when i flower im going to switch from the 600w hps to 2 1000w parabolic units. so the heater is going off and the exhuast is going to be 24/7.

well see how the heat issues play out. if it becomes a problem that seems life threatening i will post pics and open the door to the rest of the basement.