how long to grow before i sex my plants

i want to sex my plants under 2 sets of t5 ,the fixtures hold 6 tubes ,so they will be growing under 12 tubes of t5.how long do i have to grow before i can sex my plants.i only want sex them then move ouitside. thanks

as long as you want really. the question is how big of plants do you want to have?keep in mind they'll double or tripple in height.

personally, i would grow them to one foot, top them and let them grow to 1.5-2 feet or whatever, (maybe top again and after they recover) put them into flower. once you can tell the males from the females transplant the females outside and let nature take its course. they may go back into veg for a few months and then flower, but by the time you harvested you would have MONSTER bushes with 2-4 "donkey-dick" colas

You can switch the light cycle to get them to flower at any time, they won't start to show sex until they are mature however, usually at least 2 weeks. Keep in mind that they may go into shock if you put them back into veg after starting to flower this may take a while to recover from and/or cause them to hermie. If you're in the northern hemisphere you have plenty of time to take clones, flower the clones, and determine the sex of each of your plants. If you are in the southern hemisphere, I'd suggest sexing them now and get them outdoors soon.

crashcourse said:

i want to sex my plants under 2 sets of t5 ,the fixtures hold 6 tubes ,so they will be growing under 12 tubes of t5.how long do i have to grow before i can sex my plants.i only want sex them then move ouitside. thanks

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you will have to waite till they are mature befor flowering

i want to havest about 25 plants.5 spots of 5 plants.so to havest this many ,going to have to start about 5o plants so i need to sex them early cause there is so many plants in the begining.i was think let them grow to about 6 inches or 5th set of leaves.i dont want feminized seeds only cause of spoiling crop.hermies flower quickly if you dont catch them right away.
can i be able to this in one month

acually i would like to do them in 6 weeks,4 weeks to grow and 2 weeks to sex them.is this ok

I have 2 plants that will not sex. One is about 2.5 feet and the other is 2 feet. In the same group, I had 5 plants all about the same size and they did sex in one week. Do some just take longer than others?