i've noticed on some of our older plants which are close to harvest 2-3 wks. and my question is this. what causes the leaf stem to turn a purple/red? is thst part of the processor perhaps a indication that harvest is near?
This is ur plants way of saying "Hey I need more phosphorus!!" During flowering cannabis uses a significant amount more phosphorus and potassium than in vegetative growth. This is a common occurrence (reddened/purple petioles) in bloom (at least indoors). This is often accompanied by the upper portion of the plant's stem turning purple/red or get purple/red stripes. I would recommend upping the phosphorus (bloom nutes 2nd #) when U 1st notice this. Being that u are late into flower I wouldn't worry about it. Many people believe that this isn't a big deal. I did it so much that I thought it was normal until recently I've been working on remedying this. Click the Follow My grow link in my signature and U can see I too dealt with the exact same thing U are describing. U can still have a killer harvest, but I want to find out how much better it will be once this is corrected. Hope this helps and welcome to our forums.
at 2-3 weeks till harvest i would think it might be nitrogen because usually people don't give as much nitrogen in the flower stage and nitrogen starts to run out, the later stage of N deficiency is red stems along with the yellowing leaves
sure it could just as easy be phosphorus too. heck it could be sulfer deficiency too