Recurring yellow leaves

[cbdhemp808]

Notice there's also yellowing at the top, so the theory of stealing N from lower leaves doesn't seem right to me.

a week ago

yesterday

Researching this a bit more... the symptoms seem consistent with sulfur (S) and Mg deficiency, both of which can be confused with N deficiency. There seems to be plenty of N, as is seen with the deep green leaves.
These leaves ... looks very much like S deficiency... a uniform fading to yellow, and necrotic tips.

This article speaks about S deficiency starting in mid-plant, and mentions S as "partially mobile". See the photo, Figure 4, in the article...

https://www.cannabisbusinesstimes.com/article/upper-leaf-chlorosis

Also, read this about Mg deficiency...

Curing Magnesium Deficiency in Cannabis - RQS Blog

Micronutrient deficiencies are avoidable and in the worst case scenario, very treatable. Magnesium deficiency is a common problem. Here’s how to solve it.

www.royalqueenseeds.com

Doc is using Langbeinite... could be exactly what this plant needs... K, Mg, and S. BUT... better to use DTE's solution grade Langbeinite in the white bag...

 

[Emilya Green]

Notice there's also yellowing at the top. Some of this looks like N, other like K.

a week ago

yesterday

What is the point you are trying to make that it is yellowing at the top? All this means is that the deficiency has reached such a point that the plant is now needing to steal from leaves even up there. This however does not point to either N or K so I don't know what you mean when you say that it "looks" like N. Sure, they look similar, but N and K can both yellow the leaves in the same way, so there is little in that color to distinguish one from the other.

The time we are at in the grow however points to something other than N being the problem. What makes you insist that it is N, in the middle of bloom when the N requirements have dramatically dropped? The tell tell signs that I see, that it is K that is being taken from the top of the plant, is the elongated necrosis at the leaf tips... so much so that some of them have curled in a full loop upward! Only a K deficiency does this.

I'm sorry to be so argumentative about this, but you got to give us more than just that it looks like N. The OP needs to know exactly why you think it looks like N to you, so that you can explain why you are diagnosing a problem that usually happens in veg. Just because some of the leaves are going totally yellow does not necessarily indicate N is the problem. All this yellowing process indicates to me is that the plant has written that leaf off, and has dutifully drained it of all goodness before casting it away. This total yellowing is not an N deficiency phenomenon, it is part of the normal process a plant uses when removing leaves.

My experience says that throwing more N at the plant at this stage is not only not going to fix this problem, but it could make things much worse. Let's make sure we take all factors into account and have an accurate diagnosis before recommending a fix.

 

[cbdhemp808]

Sorry, I just did some editing on my last reply.

more...

What is the point you are trying to make that it is yellowing at the top? All this means is that the deficiency has reached such a point that the plant is now needing to steal from leaves even up there. This however does not point to either N or K so I don't know what you mean when you say that it "looks" like N. Sure, they look similar, but N and K can both yellow the leaves in the same way, so there is little in that color to distinguish one from the other.

No, I don't think in the same way. Deficiency of N, K, Mg, S... all can yellow leaves, but not in identical ways... there are subtle and not-so-subtle differences.

The time we are at in the grow however points to something other than N being the problem. What makes you insist that it is N, in the middle of bloom when the N requirements have dramatically dropped? The tell tell signs that I see, that it is K that is being taken from the top of the plant, is the elongated necrosis at the leaf tips... so much so that some of them have curled in a full loop upward! Only a K deficiency does this.

Hmm. No, I am no longer attached to N on this diagnosis.

I'm sorry to be so argumentative about this, but you got to give us more than just that it looks like N. The OP needs to know exactly why you think it looks like N to you, so that you can explain why you are diagnosing a problem that usually happens in veg. Just because some of the leaves are going totally yellow does not necessarily indicate N is the problem. All this yellowing process indicates to me is that the plant has written that leaf off, and has dutifully drained it of all goodness before casting it away. This total yellowing is not an N deficiency phenomenon, it is part of the normal process a plant uses when removing leaves.

My experience says that throwing more N at the plant at this stage is not only not going to fix this problem, but it could make things much worse. Let's make sure we take all factors into account and have an accurate diagnosis before recommending a fix.

Yeah, I wasn't suggesting adding more N... dunno where you got that from.

 

[Emilya Green]

let me show an example from my own garden.

These plants were experiencing a potassium deficiency about a week after transplant because it wasn't getting good access to my nutes. A couple of lower leaves went totally yellow and fell off. Not being one to remove damaged leaves, I corrected the nutrition problem and watched those leaves get totally green and healthy again, and then a month later the same plants were doing amazingly well with almost totally recovered leaves.

 

[Emilya Green]

Hmm. No, I am no longer attached to N on this diagnosis.

OK, well I am not going tie up Doc's thread any more with my argument. If you are not attached to N, I am not sure what you are saying has caused the problem other than it could be a wide range of things. You are of course free to theorize some more but I think that Doc has enough now to make up his own mind. Since this isn't the first time he has had this problem, it is something he is doing consistently grow after grow. I also note that his plants looked great, until they didn't. This is a big clue that likely has a lot to do with the increased needs of the plant in late bloom and a macro nutrient that has been or is now in short supply. Do the math... the answer is here in the clues.

 

[cbdhemp808]

let me show an example from my own garden.

These plants were experiencing a potassium deficiency about a week after transplant because it wasn't getting good access to my nutes. A couple of lower leaves went totally yellow and fell off. Not being one to remove damaged leaves, I corrected the nutrition problem and watched those leaves get totally green and healthy again, and then a month later the same plants were doing amazingly well with almost totally recovered leaves.

Very nice, indeed. Looks more like early-stage Mg deficiency to me, and doesn't look a whole lot like OP's situation.

If you are not attached to N, I am not sure what you are saying has caused the problem other than it could be a wide range of things.

That's not fair. Seems you didn't read my last reply, or didn't see my edits...

Recurring yellow leaves

Notice there's also yellowing at the top, so the theory of stealing N from lower leaves doesn't seem right to me. a week ago yesterday Researching this a bit more... the symptoms seem consistent with sulfur (S) and Mg deficiency, both of which can be confused with N deficiency. There seems...

www.420magazine.com

 

[Emeraldo]

This is a good problem case to learn from! My first thought was N def, given the leaf tip burn and whole-leaf yellowing from bottom up. But the similarities of N-def and K-def complicate the diagnosis. I find the stage-of-life analysis compelling: given she is in flowering, it's more likely a K-def and not N.

@Doctor Trevor assuming a K def, you might try a foliar spray feeding of seaweed concentrate (0-0-4.5) to the underside of the leaves. That will at the very least slow the K-def and cannot harm your plant.

I also spray the leaves with epsom salt (1 tbsp per gallon of water). Adds magnesium for chlorophyll. The leaves love it. You will too. Cheers

 

[Listersmeghead]

That Langbeinite looks like a product I could make use of in flower. I have lots of calcium in my water, so In flower I'm adding separate sources of k and mag.
Might do the job.

 

[Doctor Trevor]

I appreciate everyone's participation in this thread.