Hey Guys!
My Lower Fan leaves are starting to turn black.
Northern Lights Auto
4/5 Weeks Old
What could be going wrong please?
Probably Nitrogen deficiency. What is your water source? Do you pH? What nutrients do you use? What grow medium?
Nitrogen deficiencies usually affect the oldest, lowest leaves first , or the entire plant becomes light colored.
Nitrogen is a mobile nutrient, which means it can move throughout the plant as needed. Cannabis needs nitrogen to keep leaves green and make energy from light. All new leaves get plenty of nitrogen to make them green and help with photosynthesis. The leaves that get the most light are the newest, youngest leaves, so the plant “wants” to give those leaves priority for getting light.
If new leaves aren’t getting enough nitrogen, the plant will start to “steal” nitrogen from the older, lower leaves, so that it can give it to newer leaves. This is what causes the yellowing and wilting of a nitrogen deficiency.
Necrotic leaves: Remove them. They’ll never get better.
Tap water: ensure you dechlorinate by setting it out ~48 hrs to dissipate the chlorine (use a charcoal filter if your tap has chlorimines).
Nutrients: you have bloom nutrients for coco coir. Are you growing in coir? Regardless, you need veg nutrients.
Remove the old dying leaves. It looks almost like your leaves may have been rubbing against eachother.
Can we have a full pic of the plant and get more info about the setup? Lights, feeding schedule, PH levels, ppms, etc?
I thinking is pH problems and nute burns but @Hellraiser and @Covertgrower they can help you
@mefis It absolutely could be pH. I just assumed water is pHed and I shouldn’t have. I doubt nutrient burn because he just bought nutrients 5 weeks in.
@tistef Before attempting to diagnose any nutrient deficiency, test the water pH, as it can vary widely depending on the source. It should be between 6.0-7.0. Then, check the pH of your soil. Soil: 5.8-6.8
Disregard comment about coir above. I see you’re in soil. See chart attached for reference.
Just flush you plant if you be in soil you pH should be 6.0 to 6.5
Thanks for the replies guys!
250watt HPS in a 2x2 tent. With a small fan + extractor with carbon filter. Western Australian climate. Im doing roughly 12h light 12h darkness.
I dont have a PH tester, i will buy one asap to check!
Ill also leave my tap water out for 48hour as you recommended.
I could try swap to rain water? Ive collected some recently.
I checked and my tap water has a PH of 7.5/8 according to the watercorp website. How can i lower this?
And how does one flush?
Much appreciate the help! Thanks
Ph down, or phosphoric acid to lower ph. I don’t recommend vinegar, but some growers have used citric acid.
Flushing is where twice the amount of water goes through the medium. If it’s one gallon, 2 gallons of water goes through it. And so on.
I believe its nutrient burn due to the added fertilizer in the potting soil and then ur adding more nutrients when u water .the potting soil will have at least six months worth of fertilizer in it
You realise with autos you dont have to use the 12/12 cycle u can leave ur lights on for a cycle of 18/6 you really only use the 12/12 cycle with photoperiod plants
Thanks for all the advice everyone!
Ill do the necessary corrections, hopefully ive not done too much damage. Big noob here
Lots of great information here for sure my freind.
But if I may suggest, in your free time watch some youtube on horticulture…
“Mr grow it” is an awsome sorce for information on all things horticulture.
“PA hydroponics” is great source for helping you choose the right PH meter for you, (“tip” get a good one if you can afford it, but a $15 one is better then none)
I suggest the blue lab “bluelab truncheon” ph meter it’s pricey but it never requires calibration so accuracy is never a concern.
“420 scene” is another one if my favorites with great information and a pleasure to watch…
There are just some of my favorites, it helps me to grasp things if I can see things and youtube helps in that way…
But as to your issue, I also believe you have some deficiency going on.
Definitely give them more light, at least 18hrs a day or more, you can do a full 24 hours a day if you want to with autos, but 18 will give you the same results as 24 from my experience…
I would watch some youtube on how to flush and how to ph water. And if you’re going to use nutrients you should watch some on nutrients as well.
This is very important though…
What ever the brand of nutrients you buy says to give them… only give them half of that as they are autos and are sensitive to nutrients…
So to do list is (after you have an understanding of these of course)
- Flush
- Ph your tap water that’s been left out fir 48hr (or 24hrs if you bubble it off, another thing to youtube)
- Add nutrients at half manufacturers suggested amount (if not ÂĽ strength and work up from there if she takes to it well)
Good luck my freind, you got this!
I can’t wait to see her after you revive her and you’re going to feel so good your first time playing doctor successfully. Or it did fir me anyway 
We all make mistakes i know i still do
@1HappyPappy Thank you for all the solid pointers!
Welcome to the forum! So some folks got you on the right track for your plants health issues. But as @Aussie_autos said, you dont need to be on a 12/12 light schedule with an autoflower. Is there a reason you are only giving 12 hours of light? It won’t cause any health problems but I believe your buds would be a lot bulkier if you gave them more time in the light. 18 hours of light and 6 of of dark seem to be the crowd favorite. Though some use a 20/4, 22/2, and some even keep their lights on all the time.
@BradsBudsMT Thank you!
The 12/12 was a rough estimation. I tend to leave the light on when im at home then off when im away at work ect. Just scared the house burns down if im not around haha!
But ill be trying to give it more light as you mentioned for THICC buds!