# HEAT STRESS, but its not hot...



## teddy d (Apr 26, 2011)

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...


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## Dr.Dank (Apr 26, 2011)

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?


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## Dr.Dank (Apr 26, 2011)

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


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## Roddy (Apr 26, 2011)

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


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## MosesPMG (Apr 26, 2011)

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


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## The Hemp Goddess (Apr 26, 2011)

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"


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## teddy d (Apr 26, 2011)

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


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## woodydude (Apr 26, 2011)

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


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## The Hemp Goddess (Apr 26, 2011)

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


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## StoneyBud (Apr 26, 2011)

teddy d said:
			
		

> 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.
> 
> ...


 
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.


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## Roddy (Apr 26, 2011)

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!


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## teddy d (Apr 26, 2011)

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.


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## Roddy (Apr 26, 2011)

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.....


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## teddy d (Apr 26, 2011)

Roddy said:
			
		

> 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.



			
				Roddy said:
			
		

> 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.


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## StoneyBud (Apr 26, 2011)

teddy d said:
			
		

> 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.
> 
> ...


 
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.


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## Roddy (Apr 26, 2011)

teddy d said:
			
		

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



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.


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## teddy d (Apr 26, 2011)

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.


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## teddy d (Apr 26, 2011)

MosesPMG said:
			
		

> 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.


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## bho_expertz (Apr 27, 2011)

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


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## teddy d (Apr 27, 2011)

StoneyBud said:
			
		

> 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.


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## StoneyBud (Apr 27, 2011)

Cool Teddy D, watch for stretching. Don't get your light so high up that the plant starts stretching like crazy.

I guess your thermometer isn't the type you can push into the soil?

It might be a good idea to get one of those so you know what's happening in there, temp wise.

Can you take some pics of your plants and post them?


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## teddy d (Apr 27, 2011)

yeh i wil in a day or two. i use a digital thermometer  at canopy level. should i just get a glass mercury thermometer  to push into the soil?


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## StoneyBud (Apr 27, 2011)

teddy d said:
			
		

> yeh i wil in a day or two. i use a digital thermometer at canopy level. should i just get a glass mercury thermometer to push into the soil?


 
I've used a glass thermometer in soil before, but that was when I couldn't afford to do it right. Soil probe thermometers are cheap now. $10 and up, depending on how fancy you want it.

I use a BBQ remote temp sensor. It's made for sticking the probe into a hunk of meat on the grill, but it works perfectly as a water or soil temp probe also. Its accurate also. Digital, and no wires. I can put the readout anywhere while I'm watching it. I've gone ahead and bought a second one as a backup in case the first ever quits. It's been about a year now. Not bad for $30. I've measured temps from 34F to 180F using it. 

It's a "Oregon Scientific AW129 Wireless BBQ Thermometer with Probe Thermometer and Remote"





.


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## shuggy4105 (Apr 27, 2011)

too much light....Light-bleaching is what you may be experiencing.

That chart is based on established plants.

Pics would solve any diagnosis problems....

Good luck bro,   

Shug


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## teddy d (Apr 28, 2011)

the first two are what i would expect to see from heat stress.

the second two photos are the new growth. it looks exactly like when i had massive cold stress this past winter. the "claw" like curl, and large ridges making the leaves look kinda like clay is the only way i can describe it.

will a leave develop in this manner due to cold AND heat stress? 
with the cold it took me months to figure it out cuz the temp read 70F and i was given every answer under the sun even the grow shop guys didnt know.

are both these different looking symptoms heat realated? (the strain is Nebula BTW)


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## StoneyBud (Apr 28, 2011)

Your curl could be from several of, or one of:

1. RH low on leaf surface from too much air being blown on it.

2. RH of the entire room might be too low.

3. Nutrients are too strong.

4. pH too high and causing lockout.


No way I can tell from where I am, which one or ones of those is causing your problem. 

The RH is easy. Try misting the plant lightly with plain water a couple times each day. That will radically increase the RH on the surface of the leaf. If the leaf relaxes and/or the new growth shows no sign of curl, then you've found your problem.

The nutrient strength is also easy. Water with only plain, pH adjusted water for about 4 or 5 days. If the new growth has no curl and the old growth stays looking the same, then that could be it.

Test your pH and make sure its correct. Test the run-off from your container AND what you're putting into it.

Good luck man!


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## teddy d (Apr 29, 2011)

1. I did have a fan blowing on the plants because of the temps but now it just blows above the light not on the plants at all.

2. RH averages about 50%

3. using FFOF with plain water. it burned them when they were first tranplanted but they are about 10-11 inches tall now and should be able to handle that soil from past experience with this strain.

4.water ph is between 6.1-7.0 on average ( for the first few weeks i just keep it between 6-7 since FFOF is ph balanced I have never had an issue before.

yesterday I removed the heater completely, and changed the exhaust timer to run every 30 min on 30 min off. the outside basement temp is 64F. the thermometer under the light at canopy level now reeds 77F, but it feels cold as heck in the room to me (will measure room temp now). After battling stunted plants due to cold weather all winter im really nervous about any air temps/currents/drafts under 70F.

this is what I ran into before. I million different ideas about what could be causing the "claw leaves" but every issue I addressed never helped untill I put in a heater to give the room its own stable temp seperate from the radiant heat from the bulb.

I cant imagine im seeing cold stress and heat stress at the same time, but thats really how it appears to me 

i was so confident that this would be stress free given that i have dealt with just about every issue in the book and learned to diagnose most issues right away. but this claw leaf thing seems to be a "could be 100 things" issue


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## StoneyBud (Apr 29, 2011)

64F is low for the ambient temp, depending on the root-zone temps.

In a perfect world for MJ, the soil temp would be at 75F and the above ground plant temps would be the same.

If you lower the above ground temps to 80 and then lower the root-zone to 70, it's the same thing. An average of 75 for both. MJ works this way within reason.

No, you can't take the root zone to 50 and the above ground temps to 100. That's outside the safe zone on both ends. It makes no difference that they would average the needed 75F. The averaging only works in cases where both temps are within the safe zone of 65-90.

With your ambient temps being at 64F it really makes no difference if the area the plants are in measures at 77F at canopy level. Your lights are acting as heaters for you.

Directing the flow from your fans above the plants, so that the grow area temps heat it before it hits your plants is a great idea. Blowing the 64F air right on the plants might lower the canopy area temps below the 77F you're getting.

If the "claw" went away when you raised the ambient temps of the room, then I'd say that was your cure. Part of becoming a seasoned grower involves adapting to the many cause and effect possibilities that you can run into. Temps both below and above ground are very important.

It's temping to try new strains all the time and fun to have a cool selection of weed, but it has a draw-back. You never get a strain where you're completely familiar with it's characteristics during growing. 

With new strains, you always have a learning-curve where you have to react to problems for just that strain. If this type of growing is your choice, then keeping notes on exactly what works is very, very important so you don't have to guess later when you grow it again.

Hopefully, simply redirecting the fan air to not hit the plants, but so it is warmed to the 77F temp before hitting the plants will work for you to resolve the "claw".

When you do figure it out, note it for this strain. It may not work with the next strain when you have another whole set of problems.


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## teddy d (Apr 29, 2011)

no, I think you are confused.

the grow space is a room built in the basement. the actual basement is 64, after removing the heater the abient room temp(grow space) with the light as the only heat sorce is 72, and the canopy is 77.

but when the exhaust runs it creates negative pressure in the room and draws cooler 64F  air from many cracks ect. thats what creates cold drafts. i dont have an intake inlet because the room is light tight, but a far cry from air tight.


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## StoneyBud (Apr 29, 2011)

teddy d said:
			
		

> no, I think you are confused.
> 
> the grow space is a room built in the basement. the actual basement is 64, after removing the heater the ambient room temp(grow space) with the light as the only heat source is 72, and the canopy is 77.
> 
> but when the exhaust runs it creates negative pressure in the room and draws cooler 64F air from many cracks etc. that's what creates cold drafts. i don't have an intake inlet because the room is light tight, but a far cry from air tight.


 
Sorry, without pics of your grow setup, I was guessing that you had a fan in the doorway of the grow area blowing air in.

I'll just give up now. I can't picture what setup you have without pics, so I'll quit guessing.

Good luck!


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## teddy d (Apr 29, 2011)

thanks for the help.


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## shuggy4105 (Apr 29, 2011)

I think you may be confused as to what Stoney`s saying...

Your root-zone temps may be too cold whilst your canopy is in the safe temp zone. 

Also, that the gals may be perspiring at a high rate due to the fan blowing directly onto the tops ,making the RH too low (on the leaves), causing leaf curl.

Get a simple thermometer and place it on top of your soil to see the difference. A probe will do the same job.

My two cents, have you looked into Mg def? Just a thought, looking at the curl. They also look really dark in colour...

Just another wee tip for you; Try not to be so condescending when chatting in reply, the folks here are here to help.

Good luck man

P.S the pic is of a 'cold to warm' scenario.


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## teddy d (Apr 29, 2011)

yes i did not realize exactly what he meant. i thought he was telling me how to manipulate the root temp to compensate for canopy temps.
i did not realize he was saying it could be the actual problem.

condescending? at no point was I being condescending... 

i actually just thought someone was being condescending to me! when in fact he was making a joke. tone/intent is hard to detect on the net.

I highly appreciate any and all advice. nothing i ever say is meant to be taken that way, so im sorry if thats how im coming across.

im still a beginner and am just trying to learn.

(i dont think its a mag def though cuz my ph is pretty good and the soil was burning the plants up until a wekk or two ago. now they seem to be adjusting to the "hot" FFOF.


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## shuggy4105 (Apr 29, 2011)

Transplant shock, I`ve recently experienced the same problem when moving to a slightly more acidic soil, with similiar looking effects as to which you`re experiencing too.

You`re right, it`s very hard to judge someones temprament online. Just as I may have rushed to judgement myself.

Good luck though cuz, keep us updated on the progress
Shug


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## StoneyBud (Apr 29, 2011)

You're very welcome teddy d and thank you for trying to clarify, shug.

Plant biology is a fantastically complicated field. There are thousands of things that happen within and near plants that result in what we simply see as "produce".

Each problem can be a combination of conditions and rarely is it only one condition that causes radical problems in plant growth and health.

Two very important parts of the whole are the temperatures above the ground and below the ground in the root zone. Each have a huge impact on how a plant grows, uses its available nutrients and the over-all health of the plant.

The leaf curl is perhaps, as shug has said, a result of too much moisture leaving the surface of the leaves due to rapid transpiration. Slow that transpiration down and it may end the curl on new growth. The old growth will more than likely retain the curl despite your cure.

If the new growth and the over-all health of the plant are good, then it should result in a good formation of buds and yield at harvest.


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## teddy d (Apr 29, 2011)

StoneyBud said:
			
		

> Plant biology is a fantastically complicated field. There are thousands of things that happen within and near plants.



so true! after dealing with dozens of problems. I was finally confident, and was thinking:

grow all the same strain, same pots, same soil, same enviroment, same nutes. Remove as many variables as I could. I felt so confident in my ability based on my experience observing problems before they become a huge iissue.

I was reading a forum where everyone was talking about "THE CURL" AND THAT IT IS A NITROGEN TOXICITY...


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## shuggy4105 (Apr 29, 2011)

Possible, although they most likely mean downward curl, as in taking the 'claw' effect. 

Don`t get me wrong I did mention in a previous post your gals leaves look very dark. This can be a co-symptom of many deficiencies though so not full-proof by far.

Even though you`re dealing with the same strain; each plant may have very differing needs. It`s all down to the stability of the genetics.

Any joy with a solution yet, and have you looked at the defficiency charts?

here`s some further pics of heat stress and light bleaching etc...Heat stress


Light Bleaching


Also light bleaching and heat stress


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## teddy d (May 4, 2011)

shuggy4105 said:
			
		

> Possible, although they most likely mean downward curl, as in taking the 'claw' effect.


yes but if you look at the last two pics I posted they are "claw" like. i reduced the temps for a while and the deges stopped curling up. but now about half of the larger established fan leaves have downward tip curl and the new growth is full claw. 

I think its over fert.
ive noticed yellow tips all over but not cripsy. im almost positive is nute burn. I think this strain is sensitive (nebula) cuz im using ocean forest soil with plain water. when first transplanted the soil burned the crap out of these plants so im pretty firmiliar with the way nute burn looks. but these plants are going on about a month old and they are really getting quite large Im pretty surprized to see tip burn on plants this big with not additional nutes, and curling...

btw nebula is notorious for having dark green leaves with almost a deep purple look to them , and dark purple stems.


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