Quote Originally Posted by justaseed
a plant will usually show sex(preflowers) at about 4-6 weeks from seed under 24/0 or 18/6 lighting. there is no need to switch to 12/12 to sex the plant. it will show in it's own time. be patient, this is not a hobby for those who are in a hurry. it is much better to wait til a plant has preflowers and alternating nodes before switching to 12/12. preflowers and alternating nodes show the plant is mature and will be able to produce more, better quality bud when flowered.
Thats not always the way to go though, because people might not have the room to let the plants get that big.

If you have unlimited hight wise space, then just keep them in veg and they will show on their own, but if you have a hight limit, then dont worry, just put the lighting into 12/12 and they will show, then you can carry on with 12/12 for about 2 months, maybe a little more for certain strains and you'll get your bud