I have found that with proper temps, light spectrum and 18/6 lighting and love, you can get 75% females by the end of 25-28 days...

Every single time.

Here are plants that were 40 days old... 4 outta 4 were females with my last grow which was last year.

Done properly, you only have to grow a batch about every 2-3 years to keep you up to your ears in personal stash killer smoke. Four really great plants will keep you stoned for 2 - 3 years.