ya growing from regular seeds, until you have a female. You will only really know after you put it in 12/12 obviously, but you still have to take clones before 12/12 because to take trimmings off a plant in 12/12 may hurt/confuse the trimmings, so always before... And this is still not to say the specific strain or other sources causing stress can still hermie a plant. so strict conditions are required. An example is i grew in a tent, the light was on during day light hours off at night time hours, so no light leak obviously, i tried to control everything from the temperature, humidity, nutes(not burning the plants),to light leak, and also not burning the plants due to having them to close to the light(which did happen on this one in particular, due to becoming to big) So doing everything a grower should do, keeping mental notes of what you did or anything that has happened to the plants during flowering. Some of the conditions for my plant in particular, were, before flower she was semi-root bound, cleared that up and waited 10 days to put her in 12/12. also the size issue, over a period of time the plant was heat stressed some, the top was also removed (it was past the light and pretty much died) and the rest was bent down(this happens around 6 or 7 weeks tho) so
then i determined how far along i started seeing male flowers. which came around 12 weeks, just before harvest. This was a Sativa maybe sativa Dom. from a bagseed tho.
Overall this plant never really showed signs and maybe did this stunt because this is sometimes it's natual mechanism to produce seeds, or that it has hermie genes, i dont think its was left in to long either, due to what i was reading through to scope, it really wanted to go 3-4 more weeks, which is perfectly fine for some Sativa strains, and only under a 400 watt hps is not the best. So clones were still kept and going to try once more and see before i dump it or collect pollen then this next time, to put with another nice strain i have, this strain was still really awesome, with a few seeds lol ,
try and message me if you'd like to know more, or try to go see a few of my posts, where there are some pics, Hope some of that helps