I have never heard of anyone trying to grow cannabis with a blacklight. It won't work. I think your plants will die unless you give them at least some fluorescent light. High Intensity Discharge lights cost a lot more ,but are worth every penny when you look at your end results.
I know a guy trying to grow 6 plants under blacklights, He said they were growing alright,but i found it hard to believe i seen 1 of em and it was about 5" tall with 2 tiny leaves thats after 4 weeks,it looked pale and droopy and shit, I tried to tell him about it loads of times, but he dont listen LOL CWL
no good at all. a plant needs light in the red and blue wavelenghts. blacklights dont have this. buy some cheap fluros or betta still a hps light
Put it this way. using blacklights is the equivilent of waiting till your plants are done with flowering, then throwing them in the garbage, just a waist of time m8