when or how will i know if my seedlings are male or female?

[Mo. G]

I think Purple Kush is a clone only strain bro.
Sorry,I don't think you have Purple Kush if it was a seed.
Unless it was selfed?

I don't know how it works all together but my buddy had 6 seeds from his p kush harvest and gave them to me so I'm assuming their p kush right? But the question still remains. Once I determin the sex,if female do put back into veg or take cuttings once determined? I wanna mother the strian if female
Thankx to all for info!!!