so i have 16 seedlings of various strains all between 2-3 weeks old, and i have to make a choice on what to do about sexing. i can a- take clones of every plant, keep track of em, and flower the clones.. or i can b- start 12/12 cycle and weed out the males then bring back to a 24/7 schedule. which is fastest? will putting into 12/12 then bringing back cause enough stress to make hermie? .. i feel that since i have several strains they will react differently and some may take longer to sex than others. what say you, grasscity?
Have you topped them? that can cause them to show sex while still in veg. If you don't want to do that, there is no problem with putting them in 12/12 until they show sex and then putting them back in veg. The only time a plant will have a problem with this is if it has already gone through a lot of stress.
Simply use a magnifier to look for preflowers. As long as you are on a light schedule with darkness (19/5 for me), mj will show preflowers by week 4 veg 100%, at least i've never grown a plant from seed that didn't show sex by week 4 veg of @100 strains grown. Many will show by week 3. I find a 7x eyelupe to be most efficient. Good luck and keep it simple!
I just weed out the males, and bring the best performing female back to veg to make her a mother plant... but I'm fairly impatient when it comes to sexing. Either way is fine, but I think flowering clones to determine sex can take a lot of unnecessary time. Most strains - not all - will show sex in veg under an 18/6 (19/5 should work just as well) light schedule around week 4. I've never heard of topping causing plants to show sex, but I have heard that using flowering nutes - like Foxfarm's Open Sesame - in week 4 of veg can induce pre-flowering.