ClobberWatts
Well-Known Member
Phosphorus uptake is temperature dependent. If your temps are too cold, purple stems and petioles will result. Simple as that.
Thought is was phosphorus, but didn't want to make a claim without proof. So... because I am a hydro guy and my water temperatures were the same... could that be the reason that I did not see purple in those greens I got in the cold temperatures?