Recurring yellow leaves

[Doctor Trevor]

My CB Dutch treat, Janet, is about three weeks into flowering. She looks good except for the growing number of yellow leaves. I've given her nitrogen suppliments for the last few weeks, but the leaves keep popping up.

Any ideas?

 

[Listersmeghead]

At first glance to me doc it looks like a classic ask for potassium k.
Whether it's a simple case of raise k levels or k locked out is the next question.

 

[Doctor Trevor]

I'll get some potassium tomorrow.

I've been careful with the pH to avoid any lockout.

 

[cbdhemp808]

What's up Doc?!

I'm pretty sure this is nitrogen and/or sulfur deficiency. Also, iron is needed for proper uptake/use of N. Also, keep in mind that Fe, Zn, Mn are interrelated plant nutrients affecting uptake/use of N and S.

If this was my plant, I would fertigate with solution grade potassium sulfate, and top dress with kelp meal for iron and other micro-nutrients. Make sure she's getting enough phosphorous, too.

 

[Doctor Trevor]

I've been using Nutrigreen when I feed her as well as water her. She gets some every three days.

I use potassium metabisulfite when making wine. Is this the same potmeta you're talking about?

 

[cbdhemp808]

I've been using Nutrigreen when I feed her as well as water her. She gets some every three days.

The key is to look at what's in the fertilizer, and in what amounts. Cannabis needs specific amounts of macro and micro nutrients. I'm not familiar with Nutrigreen.

I use potassium metabisulfite when making wine. Is this the same potmeta you're talking about?

No, I use OMRI-listed potassium sulfate (K2SO4), not potassium metabisulfite (K2S2O5). I don't know if the metabisulfite can be used as a fertilizer.

 

[SmokingWings]

My CB Dutch treat, Janet, is about three weeks into flowering. She looks good

Looks really good for three weeks into flowering. To me it looks more like 5 weeks give or take.

She looks good except for the growing number of yellow leaves. I've given her nitrogen suppliments for the last few weeks, but the leaves keep popping up.

I figure that you are seeing the plant drawing nutrients from the largest leaves available. Then as the leaf gives up what it has the plant goes to the next smaller sized leaf and drains that one and the the next smaller one and so on. Eventually you will have just small leaves left, the ones along the stem and the sugar leaves.

Provide the nutrients that were suggested to try to slow down this nutrient drain which will allow the plant to keep the remaining leaves.

The next grow try to get ahead of the game and change your fertilizing schedule before the problems start to show. Make changes and add the nutrients you see in short supply now before the plant shows the signs of a problem. Switch over to flowering fertilizers at the time of the switch or beginning of the stimga/pistils showing. Or even a week or two before the switch so that the nutrients are already there for the uptake by the plant as the demand just starts to happen.

 

[Doctor Trevor]

thank you.

 

[Doctor Trevor]

I picked up a 5 lbs. box of Langbeinite, by Down to Earth. It was the only thing the gardening store had with sulphur (see photo for analysis and stuff).

The website said to add 2 tb per gallon of water. I'll be doing so tomorrow.

 

[cbdhemp808]

I picked up a 5 lbs. box of Langbeinite, by Down to Earth.

what I use!

 

[Doctor Trevor]

awesome!

 

[Doctor Trevor]

I gave Janet plenty of nitrogen, three days ago. With both Langbeinit and Nutrigreen. Leaves are still yellowing.
Today, I watered Janet and added 50% more Nutrigreen to the water than normally used.

I'm up for suggestions.

 

[cbdhemp808]

Hey Doc,
I see some nice deep green adjacent to old yellows, meaning they're getting enough N. I'd say clip off those leaves that have yellowed, so that you can see if there is any new yellowing going forward. Seems they are getting fairly close to harvest time. Good job!

 

[Emilya Green]

Nitrogen is not the problem... looks like potassium to me too.

 

[cbdhemp808]

Nitrogen is not the problem... looks like potassium to me too.

Nah, this is not potassium. K would be necrosis on the leaf margins and/or tips, and some yellowing. This is whole-leaf yellowing, starting at leaf tips, and little to no necrosis.

I'm pretty sure this is nitrogen and/or sulfur deficiency. Also, iron is needed for proper uptake/use of N. Also, keep in mind that Fe, Zn, Mn are interrelated plant nutrients affecting uptake/use of N and S.

 

[SmokingWings]

I gave Janet plenty of nitrogen, three days ago. With both Langbeinit and Nutrigreen. Leaves are still yellowing.
Today, I watered Janet and added 50% more Nutrigreen to the water than normally used.

At this stage it is highly unlikely that you will be able to turn around any of the nutrient deficiencies. It is possible that a leaf that is just starting to show a loss of color will start to return to a healthy green. But leaves that have turned a bright yellow or brown are not going to do this. An example that can be seen is watching a lawn grow before and after a fertilizing.

It took a couple of weeks to get the leaves to looking like that and it will take a couple weeks or more to see that the problems have slowed down and possibly stopped.

IOW, you should be able to slow down the changes in the leaf color which is a sign that the plant wa taking nutrients from some leaves and using those to help grow healthier buds and associated sugar leaves, stems, etc.

 

[SmokingWings]

I'm pretty sure this is nitrogen and/or sulfur deficiency. Also, iron is needed for proper uptake/use of N. Also, keep in mind that Fe, Zn, Mn are interrelated plant nutrients affecting uptake/use of N and S.

That shade of yellow and the way the leaf color has changed over almost the entire area of the leaf does look like a Nitrogen shortage.

There are other leaves on The Doctor's plant that look like a Potassium shortage. The yellow coloring is different shade, not as bright and it has started at the edges, running almost the whole length of the leaf finger, and working to cover the entire finger eventually. And there is more brown in those leaves at the early stages.

As each leaf gets used up it will die and probably fall off. The plant will move to the next largest leaf but since it uses up the biggest ones first the newly damaged leaves will keep getting smaller until eventually it is pulling from the oldest flower buds to supply the newest ones.

 

[Doctor Trevor]

I'll keep up with the Langbeinit and stop feeding her Instagreen.

Thanks.

 

[Emilya Green]

Nah, this is not potassium. K would be necrosis on the leaf margins and/or tips, and some yellowing. This is whole-leaf yellowing, starting at leaf tips, and little to no necrosis.

I'm pretty sure this is nitrogen and/or sulfur deficiency. Also, iron is needed for proper uptake/use of N. Also, keep in mind that Fe, Zn, Mn are interrelated plant nutrients affecting uptake/use of N and S.

Potassium deficiency can definitely cause whole leaf yellowing. The elongated tip burning that we see here is also a classic sign of potassium deficiency. At this stage of the grow, nitrogen is not needed nearly as much as during veg. It would be hard to have a nitrogen deficiency while in flower. Sulfur is a trace element in our grows and almost never shows as a deficiency... it can happen, but it would be extremely rare. Adding into the diagnosis that Iron, zinc and molybdenum are also deficient and adding to this problem, complicates this diagnosis to such a point that surely all of these elements could not be lacking and still have the plants look this good. The KISS rule says to simplify this to one thing, and that one thing is one of the macro nutrients needed at this stage of the grow, potassium.

Another clue is that this yellowing is progressing from bottom to top. This shows that the plant is able to go first to the storehouses in the lower fan leaves, and then move upward as more and more is needed. This shows that the element that is lacking is a "mobile" element in the plant. There are only 3 mobile elements... NP and K. It has to be one of them.

Also, its not too late to save this plant. Given the nutrient that she needs, this plant would easily recover within 3 watering cycles. You could immediately see the yellow stop progressing and the leaves stop dropping. Boiling banana peels would give you enough extra potassium to see a difference, fermenting them would give you even more. I suggest Terpinator, as it is a great source of extra potassium.

 

[cbdhemp808]

Potassium deficiency can definitely cause whole leaf yellowing. The elongated tip burning that we see here is also a classic sign of potassium deficiency. At this stage of the grow, nitrogen is not needed nearly as much as during veg.

If you google cannabis potassium deficiency, and look at various photos, from reputable websites, you'll see that OP's symptoms more closely resemble N deficiency. There could also be some K deficiency as well, depending on which leaves we're looking at. BUT... Doc has been addressing the deficiencies, so what we are talking about here may likely be what was previously deficient, which caused lower leaves to go yellow.

It would be hard to have a nitrogen deficiency while in flower.

Statistically speaking, I agree. But a percent of grows, when the plants reach flowering, may not be sufficiently fertilized with N and other nutes. I think this is probably more common than you think. There's multiple things factoring into this, not the least of which are growers relying on liquid ferts and getting confused as to what they should be using. Another factor is liquid fert products that are poorly labelled, contain unknown amounts of nutes, or are simply lacking completely in one or more nutes.

Sulfur is a trace element in our grows and almost never shows as a deficiency... it can happen, but it would be extremely rare.
Adding into the diagnosis that Iron, zinc and molybdenum are also deficient and adding to this problem, complicates this diagnosis to such a point that surely all of these elements could not be lacking and still have the plants look this good. The KISS rule says to simplify this to one thing, and that one thing is one of the macro nutrients needed at this stage of the grow, potassium.

If these trace elements have been used up, or were never there in sufficient amounts, then there will be negative effects – more or less. It all depends on what's in the growing medium, and what's being given for ferts. The key here is... depending on pot size and what were the inputs, trace elements could be depleted at this stage. Again, I would say this is probably a common occurrence. And then, a great looking plant starts to look a little shabby. Granted, that outcome is more likely to be due to macro-nutrient deficiencies, but not exclusively so.

I view micro-nutrients in a holistic way in terms of overall plant health, and not just in a simplified way regarding the appearance of symptoms, or the absence of symptoms. For example, if there's an N problem in the plant, the symptom of lower-leaf yellowing may simply be due to overall lack of N as an input, or it could be the result of a more complex interplay where available N is not being assimilated properly by the plant. Either situation could result in stealing N from lower leaves.

Another clue is that this yellowing is progressing from bottom to top. This shows that the plant is able to go first to the storehouses in the lower fan leaves, and then move upward as more and more is needed. This shows that the element that is lacking is a "mobile" element in the plant. There are only 3 mobile elements... NP and K. It has to be one of them.

Thanks for that reminder. Apparently also Mg and Mo are mobile. The upper leaves were robbing N, and possibly P & K, from the lower leaves. To my knowledge, the current yellow leaves will not become green again.

Also, its not too late to save this plant. Given the nutrient that she needs, this plant would easily recover within 3 watering cycles. You could immediately see the yellow stop progressing and the leaves stop dropping. Boiling banana peels would give you enough extra potassium to see a difference, fermenting them would give you even more. I suggest Terpinator, as it is a great source of extra potassium.

It's not clear from Doc if the yellowing is still progressing at this point. He's been keeping up on the ferts. I don't think this plant is in danger of not being saved.