When the leaves turn yellow in late flower

[tstick]

When the leaves turn yellow in late flower, are the plants even taking nutrients at that point? It seems like the buds begin to feed strictly off the leaves and there isn't much response from anything added to the soil (other than water)....and even the water uptake is slowed way down. I've also noticed that the pH of the runoff is more acidic than the incoming water and is much darker in color. That suggests, to me, that the root system is losing its ability to process nutrient uptake and beginning to break down and decompose. Basically, as the buds are ripening in late flower, they are only using what the plant has stored in the leaves and they aren't receiving any nutrients from the roots.

Is this correct?

 

[Soil Growth]

That's the way I understand it, plants pull less and less out of the medium as you get to the end of flowering.

And I believe this is backed up by the study of Flushing. There wasn't much difference between plants given nutrients or no nutrients during the last couple weeks. Like the plant wasn't sucking it up.

If this is true, should we be feeding a little heavier during weeks 5 and 6 to head off potential yellowing?

 

[tstick]

That's the way I understand it, plants pull less and less out of the medium as you get to the end of flowering.

And I believe this is backed up by the study of Flushing. There wasn't much difference between plants given nutrients or no nutrients during the last couple weeks. Like the plant wasn't sucking it up.

If this is true, should we be feeding a little heavier during weeks 5 and 6 to head off potential yellowing?

Possibly. I fed the maximum dosage every time I watered so I'm sure there was plenty of nutrients....But, then, within a few days into week #8, the plants started turning that bright lemon yellow -all throughout the leaf....no spots or anything....just consistent, lemon yellow. And, then after that, they started to curl up and dry up and turn brown and crunchy and exfoliate themselves.

I also noticed that all those bright, yellow leaves was changing the color of the light inside the tent. It's definitely more yellow in there....all the reflective walls. Could this have some kind of effect on the ripening, I wonder? Yellow light doesn't get discussed much. I mean, the light fixture I am using, is set to mimic a CMH spectrum and it always looked like a more pink version of MH light to me. But with all the yellow in the tent, now, it looks like HPS light when I unzip the flap!

 

[Jjgrow420]

Plants leaves shouldn't ever go yellow. If they do then there's an issue. My plants are green until harvest. They may turn purple or black maybe some red if the temps are cool. Not yellow.

 

[Southside112]

I always get a fade towards the end of my grows as well. Some yellowing for sure. I tend to ease off the nutes towards the end as well. Ymmv.

 

[Stardog FPV]

I think it has something to do with how well dialed in your nutes are for what strain you are growing. For instance, I have 88 cherries plants that have all black leaves at week 7 of flower and a white widow with yellowing leaves at week 5. Both using the same lights and nutes.

 

[Southside112]

I think it has something to do with how well dialed in your nutes are for what strain you are growing. For instance, I have 88 cherries plants that have all black leaves at week 7 of flower and a white widow with yellowing leaves at week 5. Both using the same lights and nutes.

For sure brother. Have to factor in the genetics as well. Some plants just hearty as hell. Some little sissy girls.

 

[tstick]

Plants leaves shouldn't ever go yellow. If they do then there's an issue. My plants are green until harvest. They may turn purple or black maybe some red if the temps are cool. Not yellow.

Senescence is normal and I think it depends a lot on the strain. I've always had plants go into their "Fall color" during late flower. Sometimes, I get reds, oranges, purples and very often a bright lemon-yellow. It's a matter of the plants cannabilizing the nutrients (and water) in the leaves to feed/ripen the buds. That's why I never defoliate any of those leaves -until show me they are empty!

But, what I want to confirm is that, during late flower, when senescence starts, the plants slow their uptake of water....Instead of watering everyday, it might be 2-3 days. And the plants also don't seem to be responsive to more Nitrogen...or no Nitrogen, etc. That suggests, to me, that the root system is also changing. I notice that my runoff water looks like tea and has a slightly lower pH than the incoming water. This suggests, to me, that the tiny root hairs used for absorbing nutrients, are dying and being expelled in the runoff....plant doesn't need them anymore. That's my theory, anyway. I used to just think it was the peat moss or something in the mix that was breaking down. The roots are still able to drink water -but not very quickly.

And just to clarify...the"nug meat" remains green, but everything else, right up to the sugar leaves, changes colors for me. I can't recall a single grow that had green leaves at harvest.

 

[pegboy]

It all sounds legit to me. In fact I use the lack of water uptake as one of my main determining factors as to when to chop.

 

[waytoofaded]

Senescence is normal and I think it depends a lot on the strain. I've always had plants go into their "Fall color" during late flower. Sometimes, I get reds, oranges, purples and very often a bright lemon-yellow. It's a matter of the plants cannabilizing the nutrients (and water) in the leaves to feed/ripen the buds. That's why I never defoliate any of those leaves -until show me they are empty!

But, what I want to confirm is that, during late flower, when senescence starts, the plants slow their uptake of water....Instead of watering everyday, it might be 2-3 days. And the plants also don't seem to be responsive to more Nitrogen...or no Nitrogen, etc. That suggests, to me, that the root system is also changing. I notice that my runoff water looks like tea and has a slightly lower pH than the incoming water. This suggests, to me, that the tiny root hairs used for absorbing nutrients, are dying and being expelled in the runoff....plant doesn't need them anymore. That's my theory, anyway. I used to just think it was the peat moss or something in the mix that was breaking down. The roots are still able to drink water -but not very quickly.

And just to clarify...the"nug meat" remains green, but everything else, right up to the sugar leaves, changes colors for me. I can't recall a single grow that had green leaves at harvest.

Outdoor plants are capable of staying completely green until harvest, even the coteyledon stays green.

Anyway I think tuning the spectrum toward Fall colors will not really provide any additional benefits. When the "Fall colors" are exposed, it means the chlorophyll in the leaf has severely degraded and the carotenoids and anthocyanins are showing through. Carentoids and anthocyanins aren't photosynthesizing like chlorophyll, so having a spectrum that "matches" it doesn't make sense.

 

[tstick]

Outdoor plants are capable of staying completely green until harvest, even the coteyledon stays green.

Anyway I think tuning the spectrum toward Fall colors will not really provide any additional benefits. When the "Fall colors" are exposed, it means the chlorophyll in the leaf has severely degraded and the carotenoids and anthocyanins are showing through. Carentoids and anthocyanins aren't photosynthesizing like chlorophyll, so having a spectrum that "matches" it doesn't make sense.

I used a CMH spectrum throughout the grow. I didn't tune anything to try and get Fall colors. The plants decided that for themselves. Remember, these plants are annuals. They are designed to grow quickly, produce a lot of seeds and then die -all in one season. We, as growers manipulate things so that process doesn't get to complete itself. We do it by restricting pollination. Otherwise, the natural process/goal of the plant is always to make seeds. Once the seeds are made, there is no need for the plant to stay alive. Even if it is restricted from making seeds, the plant will eventually die -again, because they are annuals. They can't stay green indefinitely.

 

[waytoofaded]

I used a CMH spectrum throughout the grow. I didn't tune anything to try and get Fall colors. The plants decided that for themselves. Remember, these plants are annuals. They are designed to grow quickly, produce a lot of seeds and then die -all in one season. We, as growers manipulate things so that process doesn't get to complete itself. We do it by restricting pollination. Otherwise, the natural process/goal of the plant is always to make seeds. Once the seeds are made, there is no need for the plant to stay alive. Even if it is restricted from making seeds, the plant will eventually die -again, because they are annuals. They can't stay green indefinitely.

Sorry I mis-read your initial post or mixed it with something else, I thought i was responding to a thread about tuning spectrums for Fall.

They can stay green until harvest, just ask anybody that's grown outdoors. I'm in Canada, some plants won't go yellow even when I harvest in October.

 

[Hollatchaboy]

I think the better question is, what deficiency is causing yellow leaves in late flower. Nitrogen? I don't believe so, because they don't need much N in late flower, so potassium? Phosphorous?

 

[tstick]

I think the better question is, what deficiency is causing yellow leaves in late flower. Nitrogen? I don't believe so, because they don't need much N in late flower, so potassium? Phosphorous?

Well, if all went according to plan, then ALL elements should be deficient in the potting mix. And the little Triangle Kush plant on the right is in exactly the same mix/everything and it's DARK green. (But it's also 20 days younger than the Tuna Kush plants, too.) The bud meat of the Tuna Kush is beautiful green and covered in trichomes. It's going into week #10 starting tomorrow, and it's supposed to be a 7-9 week strain. There's a lot of milk, but no amber yet. And one of the two plants is still throwing white pistils, so I'd say another week or two, maybe.

 

[Hollatchaboy]

View attachment 5451234

Well, if all went according to plan, then ALL elements should be deficient in the potting mix. And the little Triangle Kush plant on the right is in exactly the same mix/everything and it's DARK green. (But it's also 20 days younger than the Tuna Kush plants, too.) The bud meat of the Tuna Kush is beautiful green and covered in trichomes. It's going into week #10 starting tomorrow, and it's supposed to be a 7-9 week strain. There's a lot of milk, but no amber yet. And one of the two plants is still throwing white pistils, so I'd say another week or two, maybe.

You noticing any foxtails, on the one still throwing out pistils?

 

[tstick]

You noticing any foxtails, on the one still throwing out pistils?

Yes, a small amount. Are you thinking maybe too much light?

 

[mandocat]

Plants leaves shouldn't ever go yellow. If they do then there's an issue. My plants are green until harvest. They may turn purple or black maybe some red if the temps are cool. Not yellow.

I get lots of yellow leaves on my outdoor cannabis grows every year, as they finish up in the ground. All the other native plants outdoors here do the same sooner or later. If you grow in soil I think it is a natural result. The plants seem to be utilizing the more readily available nitrogen at the end of their life. All I can figure, as they have every thing they need in the ground.

 

[Coldnasty]

It all sounds legit to me. In fact I use the lack of water uptake as one of my main determining factors as to when to chop.

Same, they are done done when they are not up taking water anymore

 

[Nutty sKunK]

Yellowing end of flower is due to a few reasons I suspect.

Not enough N being the obvious one if only bloom nutes are used. A mixture of grow and bloom seems to be the best ime.

Too much light.

Too much K.

I only get a fade on my plants now when I purposefully reduce the N in the last week or two.

Even this girl only slightly faded with minimal N input in the last week or so

 

[Wastei]

Plants leaves shouldn't ever go yellow. If they do then there's an issue. My plants are green until harvest. They may turn purple or black maybe some red if the temps are cool. Not yellow.

This. Cannabis grows for months in its natural habitat. If they turn yellow there is a deficiency . It's probably due to the release of acids in late flower in search for phospourus and the prodcution of phytic acid for seed production.

I've had to pH compensate in late flower since started growing decades ago. Peat becomes acidic when broken down and the same goes for Coco Coir. Even more so with Pro-mix/Peat that has a ph of 3-4 without any buffers.