Heat stress or light stress

I'm just curious does anyone know is this stress caused by light or heat? Basically the leaves did this over night but only on the very tops

I'd say light stress, to me you have what looks like the beginning of foxtailing, and not the good type.
Easy way to set minimum distance for heat.
Put your hand under the light till it gets uncomfortably hot, then slowly move your hand away until it's a comfortable warm, that's min distance.

Good luck

So how do I combat that? Best to raise my lights up and turn my extraction fan on full-time and full power to stop the heat from rising?

Like is light stress basically the same as heat stress?

Light stress … based on the pretty intense cupping of the leaves. They are not the same thing.

What lights are you using and how far above the canopy are they?

Your extraction fan should be going 24x7 as a best practice. My very first crop went sour because I did not have to fan going continually and they became the victim of the dreaded powdery mildew. I've got the fan going at a little above 50% but it is going 24x7. Exchanges the air and does reduce the internal tent temperature.

I dont think that's light stress...looks like heat stress.. and like starecase said your exhaust system should be running full time included intake...

I got a 2000w phlizon Cree COB LED light on one side, and then I have 7 bars of 48Watts each LED bars from quickgrow.com there the QG LEDS and there about a foot off the canopy and the Philzon is like 2 feet.

I've added another fan so there is 3 small ones and 1 large fan and I turned my extraction fan on full-time now and I just jacked my lights up.

I'll post a picture when the lights go on in the morning but I have an Auto flower beside this strain and it doesn't seam to have the same signs of stress

too much light..especially if you say only the very tops, will turn fat colas into little blunts

Ok so if it's to much light what should I do other then raise my lights up? Should I try turning off the COB lights? But then it's only the veg lights on.

Raise them up. One foot is too close for those leds.

These plants that are showing heat stress are both in hydroponics and then there is an Auto flower in soil beside the 2 showing heat stress, that is not showing heat stress.

So that led me to think that possibility of it bring a deficiency of mag or something or to low humidity? I'm not sure why if it's heat stress why the one doesn't show any signs of heat stress. Or is that strictly happening because it's in soil and can withstand the higher atmospheric temperature?

Your girls turned out nice man. Don't over think it. Those are some nice frosty nugs. Different plants do different things. I'd say your t3mps are a little high at canopy. Raise your lights a little next run but plants from seed will never all be 100 percent equally as healthy. And never compare autos to photos . you will learn the hard way

Which QGs do you have?I was looking at the 4000k ones combo I thinh there called.

Yea I have the Ultimate ones for the QG's 4 foot bars and 8 bars on the rack. They are great lights, and I mean great. They only do half my 5x5 tho. They don't have a lot of coverage but the canopy penetration is amazing. My buds are like tops all the way down.

I'll be getting rid of the Cree COB in another tent cuz it runs to hot and getting another 4 foot section of QG's of 8 bars.

Ya I know that the auto is a seed we just threw it in for fun and the two purple candy's in hydro are regulars but from clones

Tslim403 said:

Yea I have the Ultimate ones for the QG's 4 foot bars and 8 bars on the rack. They are great lights, and I mean great. They only do half my 5x5 tho. They don't have a lot of coverage but the canopy penetration is amazing. My buds are like tops all the way down.

I'll be getting rid of the Cree COB in another tent cuz it runs to hot and getting another 4 foot section of QG's of 8 bars.

Click to expand...

How close together do you have them?

How close together are the bars of lights?

Tslim403 said:

How close together are the bars of lights?

Click to expand...

yes,I see you have 8 in 4ft so 6" apart I assume.

No right now there is 7 I have them beside a phlizon Cree COB LED light nut that one fried my buds it's to hot so it's taking that one and using it for a 4x4 tent on its own, I think if it's at the roof it will do the whole tent. And I just purchased 3 more QG 's for a total of 10 but I think I'll put 5 on one side and 5 on the other with something blurple in the middle or I might go for a rack of 8 and 8 and have 16 in the one tent.

Here are some pictures of my existing lights and the rack I just got with the 3 new QG 's .

The boxes are new lights and the silver racks are the new ones I just got not sure if I like them compared to the old rack.

Sweet. Looks like your about 10/12” above the canopy?I only have two of the ultimate. Sure are pricey.

heat + too much light = stressed leaves



my girl's leaves displayed stress when i used both lights on the 2000w philzon cree cob
i ended up having to turn off half the lights because the very top of my buds were becoming white (light bleached.) had to remove to prevent budrot...
mfg recommends 24-30' away, yet my plant tops are 16' away from light

also wasn't monitoring PH close enough..


I'll have to buy a 7-8" tent vs my 6ft... or top a 2nd time next grow... or try main lining...