Yellowing with 3 weeks to go?

[static123]

Hello lovely people, here I have a purple kush auto, she has 3 weeks to go give or take and almost over night she’s gone a bit yellow, should I Flush ?

Info -
Strain Purple kush Auto
12L - soil pots with Bio bizz soil.
Nutrients - bio bizz and following their guid on amounts etc.
Lights - LED (amazing quality)
Light cycle is 18/6
She is drinking 3L every two days.
Temps are between 75 / 79
Humidity 55 70

Many thanks

 

[zigzagman1960]

LED lights require 84f ambient during lights on for proper nutrient uptake—my plants looked exactly like yours my first LED grow. Then I did the the research as should you. cal-mag seems to be required every watering as well with LEDs. You’ll probably get a ton of responses, but do look into LST for cannabis using LEDs. It’s all about leaf surface temperature.

 

[Scarred4life]

A little yellowing near the end of flower is completely normal. As the plant ages it naturally sucks nitrogen out of the leaves to finish up her flowers. She doesn't look to have any specific deficiency, she just looks terribly underfed to me. Not familiar with the nutes you're running. I'd also recommend dropping that light down to around 12 - 18 inches from her. If she's only got a few weeks left there is no point in trying to keep her green. Full intensity for the rest of her days. Feed her and blast her with light. Gas pedal to the floor, who cares, you're going to chop the car up in 3 weeks.

 

[Scarred4life]

A note about leaf surface temperature.

When it comes to LST, growers should follow these basic guidelines:​

• Most cannabis plants’ LST should fall between 72 and 86 degrees – generally warmer than the ambient air.
• LST varies depending on individual cultivar. For example, plants that have evolved in colder climates can generally tolerate cooler temperatures. The same can be said for those evolved in equatorial or temperate climates.
• CO2 availability also plays a role in LST; CO2 generally raises the target temperature for photosynthesis.

 

[Listersmeghead]

Hello lovely people, here I have a purple kush auto, she has 3 weeks to go give or take and almost over night she’s gone a bit yellow, should I Flush ?

Info -
Strain Purple kush Auto
12L - soil pots with Bio bizz soil.
Nutrients - bio bizz and following their guid on amounts etc.
Lights - LED (amazing quality)
Light cycle is 18/6
She is drinking 3L every two days.
Temps are between 75 / 79
Humidity 55 70

Many thanks

Beautiful kush plant static..
As scarred4life has said, it's quite normal for this in late flower.
The plant uses a little more potassium(k) in this phase. I personally give a little extra terpinator (k supplement) in the last 3-4 weeks.
Only a tiny bit though as it's easy to over do it.

 

[static123]

LED lights require 84f ambient during lights on for proper nutrient uptake—my plants looked exactly like yours my first LED grow. Then I did the the research as should you. cal-mag seems to be required every watering as well with LEDs. You’ll probably get a ton of responses, but do look into LST for cannabis using LEDs. It’s all about leaf surface temperature.

Hey thanks for that info I will definitely take a read online.

 

[static123]

A little yellowing near the end of flower is completely normal. As the plant ages it naturally sucks nitrogen out of the leaves to finish up her flowers. She doesn't look to have any specific deficiency, she just looks terribly underfed to me. Not familiar with the nutes you're running. I'd also recommend dropping that light down to around 12 - 18 inches from her. If she's only got a few weeks left there is no point in trying to keep her green. Full intensity for the rest of her days. Feed her and blast her with light. Gas pedal to the floor, who cares, you're going to chop the car up in 3 weeks.

Hey, I am glad there is nothing else going on apart from lack of feed, they have some nutrient burn on the tips so was a little unsure if I should up the amount of nutrients added to the water, perhaps I need to feed more frequently?

 

[static123]

A note about leaf surface temperature.

When it comes to LST, growers should follow these basic guidelines:​

• Most cannabis plants’ LST should fall between 72 and 86 degrees – generally warmer than the ambient air.
• LST varies depending on individual cultivar. For example, plants that have evolved in colder climates can generally tolerate cooler temperatures. The same can be said for those evolved in equatorial or temperate climates.
• CO2 availability also plays a role in LST; CO2 generally raises the target temperature for photosynthesis.

That’s brilliant thanks loads

 

[static123]

Beautiful kush plant static..
As scarred4life has said, it's quite normal for this in late flower.
The plant uses a little more potassium(k) in this phase. I personally give a little extra terpinator (k supplement) in the last 3-4 weeks.
Only a tiny bit though as it's easy to over do it.

Thanks for the info, I was reluctant to up the amount of nutrients as there is some nutrient burn on the tips, perhaps i should feed her more frequently?

 

[Scarred4life]

Nutrient levels can be increased as light intensity is increased. It's part of the law of minimums. Growth potential is limited by the lowest level of necessary factors. Good on you for watching for toxicity. That is the other law that concerns us. Everything you add will have an upper limit. It's our job as growers to read the plant and determine when to give it gas or back off. I don't see any burn that's significant enough that I'd worry, like I said, only got a matter of weeks to go. And always remember, everything is a learning experience, another chance to grow if you will.

 

[zigzagman1960]

A note about leaf surface temperature.

When it comes to LST, growers should follow these basic guidelines:​

• Most cannabis plants’ LST should fall between 72 and 86 degrees – generally warmer than the ambient air.
• LST varies depending on individual cultivar. For example, plants that have evolved in colder climates can generally tolerate cooler temperatures. The same can be said for those evolved in equatorial or temperate climates.
• CO2 availability also plays a role in LST; CO2 generally raises the target temperature for photosynthesis.

This does NOT address LEDs. LEDs (as I’ve said a bazillion times) require 84f for a leaf surface temp of 88f.

 

[Roy Growin]

Thanks for the info, I was reluctant to up the amount of nutrients as there is some nutrient burn on the tips, perhaps i should feed her more frequently?

The plant is pretty much using up what's stored in the leaves and will likely continue to do that whether you feed or not
The yellowing, to me, is no bad thing; In the last few weeks of flower I taper feed off, eventually to zero
Not so important with Bio, but I do see it as simply a waste of nutes since the plant slowly stops drinking>feeding towards the end of flower anyway
Just my tuppence
btw - never measured anything except ml/L and pH of nutes

 

[SmokingWings]

A little yellowing near the end of flower is completely normal. As the plant ages it naturally sucks nitrogen out of the leaves to finish up her flowers. She doesn't look to have any specific deficiency, she just looks terribly underfed to me. ......... If she's only got a few weeks left there is no point in trying to keep her green. ...

Yes.

Om top of that the roots are pretty much dying off and no longer absorbing or storing nutrients. It gets to the point where often the plant does not even take in any water as others have mentioned.

The roots shutting down is why many here state that the best thing to do is to build up a decent and healthy root mass before the plant goes into flower because what is there is all there is going to be. The plant is no longer producing enough root hormones to replace any roots that have started to die back.

 

[Scarred4life]

This does NOT address LEDs. LEDs (as I’ve said a bazillion times) require 84f for a leaf surface temp of 88f.

On the contrary. Link to the full article: Optimizing Your LED Spectrum for Leaf Surface Temperature - Cannabis Industry Journal

 

[Scarred4life]

This does NOT address LEDs. LEDs (as I’ve said a bazillion times) require 84f for a leaf surface temp of 88f.

Lst is only one part of VPD. There are too many variables, in too many cultivars to ever say that one temperature is an overarching "correct" value. While targets can be set, everything is on a curve, never a set point.