Normal, or death? Northern L auto flower

[Tedmarx38]

Sprouted in early December. Temp stays at 77 max and around 40% rh. I only water when the 3 gallon fabric sack feels light and continue til it drains out the bottom (every three days, 3/4 gallon water per watering session). Feed 20-20-20 once a week. 200 Watt spider sf-2000 about 25” above it. PH adjusted down from 8.1 to 6.6.

The yellow appeared suddenly and from the top down, and per above it doesn’t fit the descriptions for over/under watering, light burn or over feeding.

Im thinking either it’s normal later-life yellowing or too little fertilizer. Appreciate your views, thanks.

 

[Sativa1970]

There three possible causes;

1)Could be at the end and it is pulling reserve nitrogen from leaves to finish the buds. check the trichomes.

2)Could be watering issue. Over watering, or uneven watering, or root rot. Sounds like you have that eliminated.

3)Could be lock out. 20-20-20 is not the right balance for flower. What nutes are you using and what medium are you in? High P will lock out N,mag and cal. Mag and cal transport N up the plant. You should be closer to 3-12-6. This is including nutrients from the soil mix if that is what you are using.

 

[Bill284]

Sprouted in early December. Temp stays at 77 max and around 40% rh. I only water when the 3 gallon fabric sack feels light and continue til it drains out the bottom (every three days, 3/4 gallon water per watering session). Feed 20-20-20 once a week. 200 Watt spider sf-2000 about 25” above it. PH adjusted down from 8.1 to 6.6.

The yellow appeared suddenly and from the top down, and per above it doesn’t fit the descriptions for over/under watering, light burn or over feeding.

Im thinking either it’s normal later-life yellowing or too little fertilizer. Appreciate your views, thanks.

Hello @Tedmarx38 beautiful lady my friend.
I do believe your feeding the wrong nutrient for her. (20-20-20)
The yellowing seems a bit premature.
What are you feeding?

Stay safe
Bill

 

[SmokingWings]

The yellow appeared suddenly and from the top down,

That is a big clue of where to start looking for a cause to the problem.

I doubt that the yellow appeared suddenly or overnight or even over a week. If it appeared suddenly then we would not know that it went from the top down. It would help if we had photographs from earlier so we could tell the progression of the yellowing across the leaf which can be another clue as to what is going on.

Going from the top down is usually a sign that an immobile nutrient is involved because new growth is affected. If it went the other way it often is a mobile nutrient because the plant can take from the older leaves causing them to turn yellow while the new leaves are green until eventually the plant takes from those leaves.

However, as the others have mentioned, the fertilizer blend could be at fault. When the Marijuana plant starts to flower it will not demand as much Nitrogen as it did during the vegetating stage. My experience with fertilizer blends that have an N-P-K of 20-20-20 are that they are not slow release. They tend to contain fast release water soluble nutrients and often the plant gets more of any or all the nutrients than it needs.

Looking at Mulder's Chart it shows that excess Nitrogen (N) can cause an 'antagonistic' reaction towards Potassium (K). The plant reacts by not being able to take up or use the K. On top of that if there is too much Phosphorus (P) then there is an antagonistic reaction towards the K again so a double whammy as some would say.

This link below shows and explains some of what 'Mobil and Immobile Nutrients' are and which is which. It is from the Northeast Region Certified Crop Adviser (NRCCA) out of Cornell University. It appears to be part of a study guide suitable for printing for an introductory class to plant nutrition but it can be read online. While it does not specifically mention Cannabis plants the info applies to most or any plant we would try to grow. As to a copy of Mulder's Chart there are all manner available for downloading. Just do a web page search using google or your favorite search engine.

https://nrcca.cals.cornell.edu/soilFertilityCA/CA1/CA1_print.html

 

[Tedmarx38]

That is a big clue of where to start looking for a cause to the problem.

I doubt that the yellow appeared suddenly or overnight or even over a week. If it appeared suddenly then we would not know that it went from the top down. It would help if we had photographs from earlier so we could tell the progression of the yellowing across the leaf which can be another clue as to what is going on.

Going from the top down is usually a sign that an immobile nutrient is involved because new growth is affected. If it went the other way it often is a mobile nutrient because the plant can take from the older leaves causing them to turn yellow while the new leaves are green until eventually the plant takes from those leaves.

However, as the others have mentioned, the fertilizer blend could be at fault. When the Marijuana plant starts to flower it will not demand as much Nitrogen as it did during the vegetating stage. My experience with fertilizer blends that have an N-P-K of 20-20-20 are that they are not slow release. They tend to contain fast release water soluble nutrients and often the plant gets more of any or all the nutrients than it needs.

Looking at Mulder's Chart it shows that excess Nitrogen (N) can cause an 'antagonistic' reaction towards Potassium (K). The plant reacts by not being able to take up or use the K. On top of that if there is too much Phosphorus (P) then there is an antagonistic reaction towards the K again so a double whammy as some would say.

This link below shows and explains some of what 'Mobil and Immobile Nutrients' are and which is which. It is from the Northeast Region Certified Crop Adviser (NRCCA) out of Cornell University. It appears to be part of a study guide suitable for printing for an introductory class to plant nutrition but it can be read online. While it does not specifically mention Cannabis plants the info applies to most or any plant we would try to grow. As to a copy of Mulder's Chart there are all manner available for downloading. Just do a web page search using google or your favorite search engine.

https://nrcca.cals.cornell.edu/soilFertilityCA/CA1/CA1_print.html

This is sensational. Many thanks to you and to all who commented. I’ll keep working on it!

 

[Sativa1970]

That is a big clue of where to start looking for a cause to the problem.

I doubt that the yellow appeared suddenly or overnight or even over a week. If it appeared suddenly then we would not know that it went from the top down. It would help if we had photographs from earlier so we could tell the progression of the yellowing across the leaf which can be another clue as to what is going on.

Going from the top down is usually a sign that an immobile nutrient is involved because new growth is affected. If it went the other way it often is a mobile nutrient because the plant can take from the older leaves causing them to turn yellow while the new leaves are green until eventually the plant takes from those leaves.

However, as the others have mentioned, the fertilizer blend could be at fault. When the Marijuana plant starts to flower it will not demand as much Nitrogen as it did during the vegetating stage. My experience with fertilizer blends that have an N-P-K of 20-20-20 are that they are not slow release. They tend to contain fast release water soluble nutrients and often the plant gets more of any or all the nutrients than it needs.

Looking at Mulder's Chart it shows that excess Nitrogen (N) can cause an 'antagonistic' reaction towards Potassium (K). The plant reacts by not being able to take up or use the K. On top of that if there is too much Phosphorus (P) then there is an antagonistic reaction towards the K again so a double whammy as some would say.

This link below shows and explains some of what 'Mobil and Immobile Nutrients' are and which is which. It is from the Northeast Region Certified Crop Adviser (NRCCA) out of Cornell University. It appears to be part of a study guide suitable for printing for an introductory class to plant nutrition but it can be read online. While it does not specifically mention Cannabis plants the info applies to most or any plant we would try to grow. As to a copy of Mulder's Chart there are all manner available for downloading. Just do a web page search using google or your favorite search engine.

https://nrcca.cals.cornell.edu/soilFertilityCA/CA1/CA1_print.html

Going to snag that link for future reference Smokingwings. These are the more simplified charts if it helps to clarify it for you Tedmarx38. Basically if you have a large crowd of one element in line at the roots the other compounds can't get up to the front of the line. Others only get in as a couple. Never know if I am over complicating or over simplifying for people.

​

 

[Tedmarx38]

Very helpful. Many thanks.

 

[KingJohnC]

As SmokingWings pointed out it is a nutrient imbalance which is nitrogen toxicity causing the new growth to yellow. In the charts supplied by Sativa1970 confirms excess nitrogen will affect new growth while leaving older leaves unaffected. Excess nutrient buildup usually causes the pH of the grow medium to continually rise requiring greater quantities of pH adjustment fluid to counteract each watering.

I believe the general vegetative nutrient blend that is being supplied has excess nitrogen which has built up in the grow medium is converting nutrients to to longer form of ammonium and is unavailable to the plant for new growth and causing the newer upper leaves to yellow.

I would flush your grow medium with pH adjusted water until the runoff is pH 5.8 for soilless and pH 6.5 for soil. A bloom nutrient formula with lower nitrogen content should be used until 1 week prior to harvest. I week prior to harvest I would either flush the plant with only either pH adjusted water or pH adjusted water with a flushing solution for 5 - 7 days before harvest.

Do you know who the breeder the northern lights seeds are and how many days of flower the seeds require? I believe that short flower period version northern lights requires 69 days of flower to mature.

 

[Tedmarx38]

I can’t thank you all enough for the detailed and helpful tips. Via an update: I switched to 10 30 20 a couple of days ago and the beast already looks better. Cheers all.

 

[Tedmarx38]

As SmokingWings pointed out it is a nutrient imbalance which is nitrogen toxicity causing the new growth to yellow. In the charts supplied by Sativa1970 confirms excess nitrogen will affect new growth while leaving older leaves unaffected. Excess nutrient buildup usually causes the pH of the grow medium to continually rise requiring greater quantities of pH adjustment fluid to counteract each watering.

I believe the general vegetative nutrient blend that is being supplied has excess nitrogen which has built up in the grow medium is converting nutrients to to longer form of ammonium and is unavailable to the plant for new growth and causing the newer upper leaves to yellow.

I would flush your grow medium with pH adjusted water until the runoff is pH 5.8 for soilless and pH 6.5 for soil. A bloom nutrient formula with lower nitrogen content should be used until 1 week prior to harvest. I week prior to harvest I would either flush the plant with only either pH adjusted water or pH adjusted water with a flushing solution for 5 - 7 days before harvest.

Do you know who the breeder the northern lights seeds are and how many days of flower the seeds require? I believe that short flower period version northern lights requires 69 days of flower to mature.

Yeah is 420 and I don’t know the flower period. They are autoflower seeds. Many thanks!

 

[beez0404]

Just my opinion, but a plant at that stage of growth needs nowhere near that much nitrogen. I'm still learning myself but checking my nutrients they have very little nitrogen for early to late bloom.