Heat stress, potassium deficiency or something else?

MikeGanja

MikeGanja

Well-Known Member
Hi,

I grow two different strains in my second vertical grow, Aurora indica and White rhino. The Aurora indica thrive with no signs of heat stress or deficiency.


The White rhino however, has some kind of problem. Some of the leaves on the top of each plant is discolored. Each one of them looks the same. The tip of each leaf is yellow with dark spots. The inner part of the leaf is getting darker with a less flexible texture than a normal leaf. No mold or pest on the plant. PH in the reservoir during flower 5.6 - 6.1. Surface temperature on the discolored leaves 26.5 degrees Celsius. Grow room temperature 25.0 degrees Celsius. RH 45%.


My guess is potassium deficiency but it also looks like heat stress. Do you think this is heat stress or potassium deficiency or is it normal for White rhino in late bloom?
 

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mainliner

Well-Known Member
im not an expert potassium def but your ph is correct so you don't have ph lockout.

if you read the first few lines of this link it explains that too much calcium or to much nitrogen can cause a potassium def

http://www.growweedeasy.com/potassium-deficiency-cannabis

and i don't think its he's stress at 25°c , this is why i asked about your fans but you've had no probs with the other one so i presume its not heat realated.


you need to explain your feeding program buddy :)


hope this helps:)


it does look like potassium but also a little iron. ..... The link explains :)
 
MikeGanja

MikeGanja

Well-Known Member
Thanks for the input Mainliner!

I have a recirculating drip system using coco as grow medium.

I use GHE nutrients Flora Bloom and Flora Micro mixed in the "Lucas Formula" ratio. I do add extra CalMag to the formula since some growers says that I need extra Magnesium when growing in Coco. Every second week I replace the entire content in the reservoir. The EC fluctuate between 1.4 and 1.6.

The watering cycle is 20 minutes on followed by 3 hours off.

I think I have decent air circulation but the strongest circulation fan is connected to the same timer as the watering cycle. The rest of the time I have a smaller fan that move enough air to spread the heat from the grow lights ( 2 x 600 Watt Sylvana GroLux). Besides that I use Cool tubes to decrease the temperature.

I read the info you linked to (http://www.growweedeasy.com/potassium-deficiency-cannabis) on Potassium deficiency. Like you said, too much calcium can cause it. I didn't know that. :) Perhaps I have caused it with the extra CalMag?
 
M

mainliner

Well-Known Member
im sorry i cant help u further, i don't use cal mag or coco but you do need extra in coco but im just not sure about the amount sorry:(

someone will help but it looks like the calcium to me :)

good luck.
 
T

THE KONASSURE

Well-Known Member
is it the higher leaves or lower ones ?

Looks like a bit of under feeding to me maybe a bit more pk is needed have you run this strain before ?
 
MikeGanja

MikeGanja

Well-Known Member
Thanks for the help Mainliner, now I can exclude a few things from the list and you gave me a few ideas of what could have caused this problem.

THE KONASSURE: It's the highest leaves only. It's the second time with the White Rhino strain but the first time in a vertical setup and with coco as a medium. The last time I observed similar problems but only on few leaves and in the very last week of flowering. This time it's more obvious that something is less than optimal.

It's interesting that the other strain in this grow (aurora indica) grows extremely well. The AI grows short, dark leaves with a healthy texture and impressive buds. I think that you are right with the PK. Question is if I should slowly add more concentrated solution (Lucas formula) or if I should add some extra Potassium to the plants with the deficiency?

I expect that this grow is ready for harvest within 3-4 weeks so perhaps I just should keep this in mind to the next grow and not grow this strains together if they need different levels of PK?
 
thenotsoesoteric

thenotsoesoteric

Well-Known Member
MikeGanja said:
Thanks for the help Mainliner, now I can exclude a few things from the list and you gave me a few ideas of what could have caused this problem.

THE KONASSURE: It's the highest leaves only. It's the second time with the White Rhino strain but the first time in a vertical setup and with coco as a medium. The last time I observed similar problems but only on few leaves and in the very last week of flowering. This time it's more obvious that something is less than optimal.

It's interesting that the other strain in this grow (aurora indica) grows extremely well. The AI grows short, dark leaves with a healthy texture and impressive buds. I think that you are right with the PK. Question is if I should slowly add more concentrated solution (Lucas formula) or if I should add some extra Potassium to the plants with the deficiency?

I expect that this grow is ready for harvest within 3-4 weeks so perhaps I just should keep this in mind to the next grow and not grow this strains together if they need different levels of PK?
Click to expand...
Are you using 4ml micro and 8 ml bloom or 8 ml micro and 16 ml bloom, either way I would assume it is enough P and K. Also with coco I add 5ml extra to a gallon each and every watering.

While the PH in your reservoir might be balanced, the PH inside the plants container maybe off. Have you tried flushing that one plant out real good with fertilized and ph'd water. You might just have an imbalance inside the coco of just that one plant.
 
MikeGanja

MikeGanja

Well-Known Member
thenotsoesoteric said:
Are you using 4ml micro and 8 ml bloom or 8 ml micro and 16 ml bloom, either way I would assume it is enough P and K. Also with coco I add 5ml extra to a gallon each and every watering.

While the PH in your reservoir might be balanced, the PH inside the plants container maybe off. Have you tried flushing that one plant out real good with fertilized and ph'd water. You might just have an imbalance inside the coco of just that one plant.
Click to expand...

I flushed the whole system this weekend just to be sure that there is no imbalance in the containers. My latest theory is that there was a small imbalance combined with heat stress. Since my last post I have found one or two leaves on the other strain, with pale almost dry leaves. Those leaves was on the top on the plant facing the light. Only difference was that the hadn't the discoloration that look like deficiency. All the dry or almost dry leaves was close to the Cool tube.

I added another fan to increase the air flow and handle the heat from the grow lights.
 
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