My plants are 5 days into pre flowering. At what point can I change to a 12/12. When sex can be told or sooner (and if sooner, will sex be shown sooner)? I have my plants fighting for space and need to ditch the males to get space back.
Rule of thumb: Alternating nodes is when the plant is ready. Though they can really go in anytime they are past the seedling stage.
They can go into flower right from the seedling stage if you so choose. Put them into flower before the seed casing is gone if you like... To answer the first question, I like to see the sex. If you look real hard, and with a little experience you should be able to tell the fems and males before any pistils form from the female preflowers. I use a 24/0 light system and have my males out by around the 5 week mark of veg.