How soon can I sex?

I am growing in soil from seed
I only have 2 at the moment as genetics aren't easy to get where i am.
I'm waiting on a bunch of auto flowers from seedsman seeds.

The two I'm started so far just broke soil today
I don't want to waste my time on males so was wanting to sex them asap
If I put them into cups how soon can I put them under 12/12 to sex?
Then after I know if either of them are female i was going to put them back into veg for 5 or 6 weeks
Is this doable and when can I start ?
Any tips or advice would be greatly appreciated
Thanks in advance

As early as 4 to 6 weeks, when the nodes become asymmetrical.
I found this video the most useful.

Prince Vegeta said:

I am growing in soil from seed
I only have 2 at the moment as genetics aren't easy to get where i am.
I'm waiting on a bunch of auto flowers from seedsman seeds.

The two I'm started so far just broke soil today
I don't want to waste my time on males so was wanting to sex them asap
If I put them into cups how soon can I put them under 12/12 to sex?
Then after I know if either of them are female i was going to put them back into veg for 5 or 6 weeks
Is this doable and when can I start ?
Any tips or advice would be greatly appreciated
Thanks in advance

Click to expand...

You can run 12/12 from seed if you want, it works okay. I run 18-20 hours a day for three weeks then go to 14 hours until they show.

So then that means i CANT throw my seedlings into flower then revert my females back to veg? To cull out my males
So i just have to wait the weeks to see huh?

Prince Vegeta said:

So then that means i CANT throw my seedlings into flower then revert my females back to veg? To cull out my males
So i just have to wait the weeks to see huh?

Click to expand...

you can do that, but it takes weeks and weeks to get them to grow right again, it's not like put them into flower for a week or two then just throw them back in veg. you're starting biological processes when you put a plant in flower, it shifts gears and starts to produce different hormones. reversing that process takes at least a month, more likely two.
you could take cuttings from your plants, mark them so you know which came from which plant, and put those in flower.

Puberty is probably the earliest. Oh sorry wrong sex, the above advice is good for long time!

Might not be that helpful but:

1) Why ever bother with autoflowers when switching a lamp's timer over is super easy and gives you control over your preferred vegging period? I have been told that autoflowers produce lower yields, though have no evidence to back that up.
2) I just buy feminised seeds, so you don't have the song and dance of sexing the plants or rogue pollination.

After the second set of branches come out in the veg cycle. Look real close where the main stem is making the branch as high on the plant as you can go, and then look for what I have posted in the pics. you can sex them before without any issues. just look there you will either see the two hairs Female or a round pod like in the pics. been doing that for years hasn't failed me yet.