algebraist
Well-Known Member
Hi all -- My newest growth is showing yellowed leaf tips, and I have one tiny necrotic (dead) spot on a fan leaf. So I think I am seeing the first signs of some problem, most likely a nutrient deficiency. The plants are in soil: 10 parts FFOF, 4 parts perlite, 1 part vermiculite; they were transplanted from 4" pots into 7 gallon cloth containers of this soil a little less than 3 weeks ago. As FFOF is rich, I haven't fertilized with anything yet.
Looking through "The Cannabis Encyclopedia" by Jorge Cervantes, my best guesses were Boron or Zinc deficiency, but he claims that boron deficiency is caused by "extremely poor soil," which I'm sure is not the case, and that zinc deficiency is caused by a pH above 7.0; I tested mine with a "rapitest" tester, using a sample about 3 inches below the surface, and it's 6.5 or slightly less.
They're under LED panels which I had at 22 inches above the plants; I raised them last night to 25 inches above, in case that was the problem. The LEDs include a couple of UVB diodes, and perhaps the necrotic spot could be due to a burn from the UV being too close -- maybe focused by a water droplet that got on the leaf during watering. Could the leaf tips be yellowing also from the light being too close?
Anyway, thanks for looking -- here are the pictures. You can see that I'm just barely starting to see yellowed tips, and the spot I'm talking about is tiny. But these are my girls...

Looking through "The Cannabis Encyclopedia" by Jorge Cervantes, my best guesses were Boron or Zinc deficiency, but he claims that boron deficiency is caused by "extremely poor soil," which I'm sure is not the case, and that zinc deficiency is caused by a pH above 7.0; I tested mine with a "rapitest" tester, using a sample about 3 inches below the surface, and it's 6.5 or slightly less.
They're under LED panels which I had at 22 inches above the plants; I raised them last night to 25 inches above, in case that was the problem. The LEDs include a couple of UVB diodes, and perhaps the necrotic spot could be due to a burn from the UV being too close -- maybe focused by a water droplet that got on the leaf during watering. Could the leaf tips be yellowing also from the light being too close?
Anyway, thanks for looking -- here are the pictures. You can see that I'm just barely starting to see yellowed tips, and the spot I'm talking about is tiny. But these are my girls...

