Will Plants Show Sex In The Veg Stage????

Will plants show sex in their veg stage? I always thought that you had to switch to a 12/12 before the showed sex. My friend told me that thats not the case. He says that they show sex in the veg stage after about 3 weeks. Is this true, does anyone have any input?

Also, another question. Are all strains capable of the holy grail of cannabis, which is .5 grams per watt per 30 days. Im trying to pick a potent strain for a larger grow, but i want to grow some conniseur bud. But before i pick my strain i want to pick somthing with 12%thc+ but i also want to achieve the .5 per watt per 30 benchmark.

Anyhelp would be greatly apriciated, i cant find the answer to any of these questions anywhere!

 

bump bump

 

Do you know if all strains are capable of the .5 per watt per 30 days of flowering benchmark?